Syllabus
TENNARD
v.
DRETKE, DIRECTOR, TEXAS DEPARTMENT OF CRIMINAL JUSTICE, CORRECTIONAL
INSTITUTIONS DIVISION
During his capital murder trials penalty phase, petitioner Tennard presented evidence that he had an IQ of 67. The jury was instructed to determine the appropriate punishment by considering two special issues, which inquired into whether the crime was committed deliberately and whether the defendant posed a risk of future dangerousness. These were materially identical to two special issues found insufficient, in Penry v. Lynaugh, 492 U. S. 302, for the jury to give effect to Penrys mitigating mental retardation and childhood abuse evidence. Tennards jury answered both special issues affirmatively and Tennard was sentenced to death. The Federal District Court denied Tennards federal habeas petition in which he claimed that his death sentence violated the Eighth Amendment as interpreted in Penry, and denied a certificate of appealability (COA). The Fifth Circuit agreed that Tennard was not entitled to a COA. It applied a threshold test to Tennards mitigating evidence, asking whether it met the Fifth Circuits standard of constitutional relevance in Penry casesthat is, whether it was evidence of a uniquely severe permanent handicap that bore a nexus to the crime. The court concluded that (1) low IQ evidence alone does not constitute a uniquely severe condition, and no evidence tied Tennards IQ to retardation, and (2) even if his low IQ amounted to mental retardation evidence, Tennard did not show that his crime was attributable to it. After this Court vacated the judgment and remanded for further consideration in light of Atkins v. Virginia, 536 U. S. 304, the Fifth Circuit reinstated its prior opinion.
Held: Because reasonable jurists would find the district courts assessment of the constitutional claims debatable or wrong, Slack v. McDaniel, 529 U. S. 473, a COA should have issued. Pp. 715.
(a) A COA should issue if an applicant has made a substantial showing of the denial of a constitutional right, 28 U. S. C. §2253(c)(2), by demonstrating that reasonable jurists would find the district courts assessment of the constitutional claims debatable or wrong, 529 U. S., at 484. Relief may not be granted unless the state court adjudication was contrary to, or involved an unreasonable application of, clearly established Federal law, as determined by this Court. §2254(d)(1). Pp. 78.
(b) The Fifth Circuit assessed Tennards Penry claim under an improper standard. Its threshold constitutional relevance screening test has no foundation in this Courts decisions. Relevance was not at issue in Penry. And this Court spoke in the most expansive terms when addressing the relevance standard directly in McKoy v. North Carolina, 494 U. S. 433, finding applicable the general evidentiary standard that any tendency to make the existence of any fact that is of consequence to the determination of the action more probable or less probable than it would be without the evidence, id., at 440. Once this low relevance threshold is met, the Eighth Amendment requires that the jury must be able to consider and give effect to a capital defendants mitigating evidence. Boyde v. California, 494 U. S. 370. The Fifth Circuits test is inconsistent with these principles. Thus, neither the uniquely severe nor the nexus element of the Fifth Circuits test was a proper reason not to reach the substance of Tennards Penry claims. Pp. 813.
(c) Turning to the analysis that the Fifth Circuit should have conducted, reasonable jurists could conclude that Tennards low IQ evidence was relevant mitigating evidence, and that the Texas Court of Criminal Appeals application of Penry was unreasonable, since the relationship between the special issues and Tennards low IQ evidence has the same essential features as that between those issues and Penrys mental retardation evidence. Impaired intellectual functioning has mitigating dimension beyond the impact it has on the ability to act deliberately. A reasonable jurist could conclude that the jury might have given the low IQ evidence aggravating effect in considering Tennards future dangerousness. Indeed, the prosecutor pressed exactly the most problematic interpretation of the special issues, suggesting that Tennards low IQ was irrelevant in mitigation, but relevant to future dangerousness. Pp. 1315.
317 F. 3d 476, reversed and remanded.
OConnor, J., delivered the opinion of the Court, in which Stevens, Kennedy, Souter, Ginsburg, and Breyer, JJ., joined. Rehnquist, C. J., Scalia, J., and Thomas, J., filed dissenting opinions.
Opinion
ROBERT JAMES TENNARD, PETITIONER
v.
DOUG
DRETKE, DIRECTOR, TEXAS DEPARTMENT OF
CRIMINAL JUSTICE, CORRECTIONAL
INSTITUTIONS DIVISION
Justice OConnor delivered the opinion of the Court.
In Penry v. Lynaugh, 492 U. S. 302 (1989) (Penry I), we held that the Texas capital sentencing scheme provided a constitutionally inadequate vehicle for jurors to consider and give effect to the mitigating evidence of mental retardation and childhood abuse the petitioner had presented. The petitioner in this case argues that the same scheme was inadequate for jurors to give effect to his evidence of low intelligence. The Texas courts rejected his claim, and a Federal District Court denied his petition for a writ of habeas corpus. We conclude that reasonable jurists would find the district courts assessment of the constitutional claims debatable or wrong, Slack v. McDaniel , 529 U. S. 473, 484 (2000) , and therefore hold that a certificate of appealability should have issued.
I
Petitioner Robert Tennard was convicted by a jury of capital murder in October 1986. The evidence presented at trial indicated that Tennard and two accomplices killed two of his neighbors and robbed their house. Tennard himself stabbed one of the victims to death, and one of the accomplices killed the other victim with a hatchet.
During the penalty phase of the trial, defense counsel called only one witnessTennards parole officerwho testified that Tennards Department of Corrections record from a prior incarceration indicated that he had an IQ of 67. App. 2829. He testified that the IQ test would have been administered as a matter of course. Ibid. The report, which indicated that Tennard was 17 years old at the time it was prepared, was admitted into evidence. On cross-examination, the parole officer testified that he did not know who had administered the test. Id., at 30. The government introduced evidence in the penalty phase regarding a prior conviction for rape, committed when Tennard was 16. The rape victim testified that she had escaped through a window after Tennard permitted her to go to the bathroom to take a bath, promising him she wouldnt run away. Id., at 1617.
The jury was instructed to consider the appropriate punishment by answering the two special issues used at the time in Texas to establish whether a sentence of life imprisonment or death would be imposed:
Was the conduct of the defendant, Robert James Tennard, that caused the death of the deceased committed deliberately and with the reasonable expectation that the death of the deceased or another would result? Id., at 69 (the deliberateness special issue).
Is there a probability that the defendant, Robert James Tennard, would commit criminal acts of violence that would constitute a continuing threat to society? Id., at 70 (the future dangerousness special issue).
  And he believed her. This guy with the 67 IQ, and she goes in and, sure enough, she escapes, just like she should have. That is uncontroverted testimony before you, that we have got a man before us that has got an intelligence quotient . . . that is that low. Id., at 51.
In rebuttal, the prosecution suggested that the low IQ evidence was simply irrelevant to the question of mitigation:
But whether he has a low IQ or not is not really the issue. Because the legislature, in asking you to address that question [the future dangerousness special issue], the reasons why he became a danger are not really relevant. The fact that he is a danger, that the evidence shows hes a danger, is the criteria to use in answering that question. Id., at 60.
The jury answered both special issues in the affirmative, and Tennard was accordingly sentenced to death.
Unsuccessful on direct appeal, Tennard sought state postconviction relief. He argued that, in light of the instructions given to the jury, his death sentence had been obtained in violation of the Eighth Amendment as interpreted by this Court in Penry I . In that case, we had held that it is not enough simply to allow the defendant to present mitigating evidence to the sentencer. The sentencer must also be able to consider and give effect to that evidence in imposing sentence. Penry I , supra, at 319; see also Penry v. Johnson, 532 U. S. 782, 797 (2001) (Penry II) (describing give effect to language of Penry I as the key to that decision). We concluded that the same two special issues that were presented to Tennards jury (plus a third immaterial to the questions now before us) were insufficient for the jury in Penrys case to consider and give effect to Penrys evidence of mental retardation and childhood abuse, and therefore ran afoul of the Eighth Amendment. Penry I , 492 U. S., at 319328. His mental retardation evidence, we held, had relevance to [his] moral culpability beyond the scope of the [deliberateness] special verdict questio[n] because [p]ersonal culpability is not solely a function of a defendants capacity to act deliberately. Id. , at 322 (some brackets in original). Moreover, because the evidence concerning Penrys mental retardation indicated that one effect of his retardation is his inability to learn from his mistakes, his retardation was relevant to the future dangerousness special issue only as an aggravating factor. Id., at 323. As to the evidence of childhood abuse, we held that the two special issues simply failed to provide a vehicle for the jury to give [it] mitigating effect. Id., at 322324.
The Texas Court of Criminal Appeals rejected Tennards Penry claim. Ex parte Tennard , 960 S. W. 2d 57 (1997) (en banc). Writing for a plurality of four, Presiding Judge McCormick observed that the definition of mental retardation adopted in Texas involves three components ((1) subaverage general intellectual functioning; (2) concurrent deficits in adaptive behavior; and (3) onset during the early development period, id., at 60), and concluded: [Tennards] evidence of a low IQ score, standing alone, does not meet this definition. Qualitatively and quantitatively, [Tennards] low IQ evidence does not approach the level of Johnny Paul Penrys evidence of mental retardation… . [W]e find no evidence in this record that applicant is mentally retarded. Id., at 61.
The plurality went on to consider whether Tennard would be entitled to relief under Penry even if his low IQ fell within Penry s definition of mental retardation. 960 S. W. 2d, at 61. It held that he would not. The court explained that, unlike the evidence presented in Penrys case, there is no evidence … [that Tennards] low IQ rendered him unable to appreciate the wrongfulness of his conduct when he committed the offense, or that his low IQ rendered him unable to learn from his mistakes … or control his impulses … . Id., at 62. It found there was no danger that the jury would have given the evidence only aggravating effect in answering the future dangerousness special issue, and that the low IQ and gullibility evidence was not beyond the jurys effective reach because the jury could have used this evidence for a no answer to the deliberateness special issue. Ibid.
Two judges concurred separately, and wrote that this Court has sustained a Penry claim only when there is evidence of mental retardation. But even in those cases, the evidence of mental retardation was always something more than what was presented in this case. 960 S. W. 2d, at 64 (opinion of Meyers, J.) (citations omitted). Taking a more permissive view of evidence of impaired intellectual functioning than did the plurality ([F]or Penry purposes, courts should not distinguish between mental retardation and dementia, even though the onset of the latter may occur after age eighteen, id., at 65), the concurring judges nevertheless concluded that the record does not contain sufficient evidence to support Tennards Penry claim. 960 S. W. 2d , at 63. The concurring judges also rejected Tennards contention that evidence of an IQ of below 70 alone requires a Penry instruction because published opinions of the Texas courts had uniformly required more. Id., at 67.
Judge Baird dissented, maintaining that the Court of Criminal Appeals had consistent[ly] held, in the wake of Penry I , that evidence of mental retardation cannot be adequately considered within the statutory special issues. 960 S. W. 2d, at 67. The court had strayed from its precedent, Judge Baird wrote, and instead of asking simply whether the jury had a vehicle for considering the mitigating evidence, had weigh[ed] the sufficiency of [Tennards] mitigating evidence. Id., at 70. Judges Overstreet and Womack dissented without opinion. Id., at 63.
Tennard sought federal habeas corpus relief. The District Court denied his petition. Tennard v. Johnson, Civ. Action No. H984238 (S D Tex., July 25, 2000), App. 121. The court began by observing that [e]vidence of a single low score on an unidentified intelligence test is not evidence that Tennard was mentally retarded. Id., at 128. It then considered whether the 67 IQ score was within the effective reach of the jury. Ibid. Noting that Tennards low IQ score was not concealed from the jury; it was in evidence, and both sides argued its significance for punishment, the court concluded that the jury had adequate means, in the two special issues, by which to give effect to that mitigating evidence. Id., at 129. The court subsequently denied Tennard a certificate of appealability (COA). Civ. Action No. H984238 (S D Tex. Oct. 17, 2000), see App. 2.
The Court of Appeals for the Fifth Circuit, after full briefing and oral argument, issued an opinion holding that Tennard was not entitled to a COA because his Penry claim was not debatable among jurists of reason. Tennard v. Cockrell, 284 F. 3d 591 (2002). The court began by stating the test applied in the Fifth Circuit to Penry claims, which involves a threshold inquiry into whether the petitioner presented constitutionally relevant mitigating evidence, that is, evidence of a uniquely severe permanent handicap with which the defendant was burdened through no fault of his own, and evidence that the criminal act was attributable to this severe permanent condition. 284 F. 3d, at 595.
The court then held that Tennard was not entitled to a COA, for two reasons: First, it held that evidence of low IQ alone does not constitute a uniquely severe condition, and rejected Tennards claim that his evidence was of mental retardation, not just low IQ, because no evidence had been introduced tying his IQ score to retardation. Id., at 596. Second, it held that even if Tennards evidence was mental retardation evidence, his claim must fail because he did not show that the crime he committed was attributable to his low IQ. Id., at 596597. Judge Dennis dissented, concluding that the Texas courts application of Penry was unreasonable and that Tennard was entitled to habeas relief. 284 F. 3d, at 597604.
Tennard filed a petition for certiorari, and this Court granted the writ, vacated the judgment, and remanded for further consideration in light of Atkins v. Virginia, 536 U. S. 304 (2002) . Tennard v. Cockrell, 537 U. S. 802 (2002) . The Fifth Circuit took the remand to be for consideration of a substantive Atkins claim. It observed that Tennard has never argued that the Eighth Amendment prohibits his execution and reinstated its prior panel opinion. 317 F. 3d 476, 477 (2003). We again granted certiorari. 540 U. S. 945 (2003) .
II
A
A COA should issue if the applicant has made a substantial showing of the denial of a constitutional right, 28 U. S. C. §2253(c)(2), which we have interpreted to require that the petitioner must demonstrate that reasonable jurists would find the district courts assessment of the constitutional claims debatable or wrong. Slack v. McDaniel , 529 U. S., at 484; see also Miller-El v. Cockrell, 537 U. S. 322, 336 (2003) (Under the controlling standard, a petitioner must sho[w] that reasonable jurists could debate whether (or, for that matter, agree that) the petition should have been resolved in a different manner or that the issues presented were adequate to deserve encouragement to proceed further ). The petitioners arguments ultimately must be assessed under the deferential standard required by 28 U. S. C. §2254(d)(1): Relief may not be granted unless the state court adjudication resulted in a decision that was contrary to, or involved an unreasonable application of, clearly established Federal law, as determined by the Supreme Court of the United States.
The State has never disputed that Tennards Penry claim was properly preserved for federal habeas review. Not only did the state court consider the question on the merits, we note that the issue was also raised by defense counsel prior to trial in a motion to set aside the indictment on the ground, among others, that the Texas capital murder statutes do not explicitly allow the consideration of any specific mitigating circumstances at the punishment phase of the prosecution and, consequently, are violative of the accuseds right to be free from cruel and unusual punishment and are also void for vagueness. Defendants Motion to Set Aside the Indictment, in Cause No. 431127 (248th Jud. Dist. Ct. Harris County, Tex., May 28, 1986), p. 4.
B
Despite paying lipservice to the principles guiding issuance of a COA, Tennard v. Cockrell, supra, at 594, the Fifth Circuits analysis proceeded along a distinctly different track. Rather than examining the District Courts analysis of the Texas court decision, it invoked its own restrictive gloss on Penry I:
In reviewing a Penry claim, we must determine whether the mitigating evidence introduced at trial was constitutionally relevant and beyond the effective reach of the jury. … To be constitutionally relevant, the evidence must show (1) a uniquely severe permanent handicap with which the defendant was burdened through no fault of his own, … and (2) that the criminal act was attributable to this severe permanent condition. 284 F. 3d, at 595 (quoting Davis v. Scott, 51 F. 3d, 457, 460461 (CA5 1998)).
This test for constitutional relevance, characterized by the State at oral argument as a threshold screening test, Tr. of Oral Arg.10, 28, appears to be applied uniformly in the Fifth Circuit to Penry claims. See, e.g., Bigby v. Cockrell , 340 F. 3d 259, 273 (2003); Robertson v. Cockrell , 325 F. 3d 243, 251 (2003) (en banc); Smith v. Cockrell , 311 F. 3d 661, 680 (2002); Blue v. Cockrell , 298 F. 3d 318, 320321 (2002); Davis v. Scott , 51 F. 3d 457, 460461 (1995). Only after the court finds that certain mitigating evidence is constitutionally relevant will it consider whether that evidence was within the effective reach of the jur[y]. E.g., Smith, supra, at 680 (court asks whether evidence was constitutionally relevant and, if so, will consider whether it was within jurys effective reach). In the decision below, the Fifth Circuit concluded that Tennard was precluded from establishing a Penry claim because his low IQ evidence bore no nexus to the crime, and so did not move on to the effective reach question. 284 F. 3d, at 597.
The Fifth Circuits test has no foundation in the decisions of this Court. Neither Penry I nor its progeny screened mitigating evidence for constitutional relevance before considering whether the jury instructions comported with the Eighth Amendment. Indeed, the mitigating evidence presented in Penry I was concededly relevant, see Tr. of Oral Arg., O. T. 1988, No. 876177, pp. 3436, so even if limiting principles regarding relevance were suggested in our opinionand we do not think they werethey could not have been material to the holding.
When we addressed directly the relevance standard applicable to mitigating evidence in capital cases in McKoy v. North Carolina, 494 U. S. 433, 440441 (1990) , we spoke in the most expansive terms. We established that the meaning of relevance is no different in the context of mitigating evidence introduced in a capital sentencing proceeding than in any other context, and thus the general evidentiary standard any tendency to make the existence of any fact that is of consequence to the determination of the action more probable or less probable than it would be without the evidence applies. Id., at 440 (quoting New Jersey v. T. L. O., 469 U. S. 325, 345 (1985) ). We quoted approvingly from a dissenting opinion in the state court: Relevant mitigating evidence is evidence which tends logically to prove or disprove some fact or circumstance which a fact-finder could reasonably deem to have mitigating value. 494 U. S., at 440 (quoting State v. McKoy , 323 N. C. 1, 5556, 372 S. E. 2d, 12, 45 (1988) (opinion of Exum, C. J.)). Thus, a State cannot bar the consideration of … evidence if the sentencer could reasonably find that it warrants a sentence less than death. 494 U. S., at 441.
Once this low threshold for relevance is met, the Eighth Amendment requires that the jury be able to consider and give effect to a capital defendants mitigating evidence. Boyde v. California, 494 U. S. 370, 377378 (1990) (citing Lockett v. Ohio, 438 U. S. 586 (1978) ; Eddings v. Oklahoma, 455 U. S. 104 (1982) ; Penry I, 492 U. S. 302 (1989) ); see also Payne v. Tennessee, 501 U. S. 808, 822 (1991) (We have held that a State cannot preclude the sentencer from considering any relevant mitigating evidence that the defendant proffers in support of a sentence less than death… . [V]irtually no limits are placed on the relevant mitigating evidence a capital defendant may introduce concerning his own circumstances (quoting Eddings , supra , at 114)).
The Fifth Circuits test is inconsistent with these principles. Most obviously, the test will screen out any positive aspect of a defendants character, because good character traits are neither handicap[s] nor typically traits to which criminal activity is attributable. In Skipper v. South Carolina, 476 U. S. 1, 5 (1986) , however, we made clear that good-character evidence can be evidence that, [u]nder Eddings , … may not be excluded from the sentencers consideration. We observed that even though the petitioners evidence of good conduct in jail did not relate specifically to petitioners culpability for the crime he committed, there is no question but that such [evidence] … would be mitigating in the sense that [it] might serve as a basis for a sentence less than death. Lockett , supra , at 604 id., at 45 (citation omitted). Such evidence, we said, of a defendants disposition to make a well-behaved and peaceful adjustment to life in prison is … by its nature relevant to the sentencing determination. Id., at 7. Of course, the Texas courts might reasonably conclude that evidence of good conduct in jail was within the jurys effective reach via the future dangerousness special issue. See Franklin v. Lynaugh, 487 U. S. 164, 177178 (1988) (plurality opinion); id., at 185186 ( OConnor, J. , concurring in judgment). But under the Fifth Circuits test, the evidence would have been screened out before the time came to consider that question.
In Tennards case, the Fifth Circuit invoked both the uniquely severe and the nexus elements of its test to deny him relief under Penry I . Tennard v. Cockrell, 284 F. 3d, at 596 (contrasting Tennards low IQ evidence, which did not constitute a uniquely severe condition, with mental retardation, a severe permanent condition); id., at 596597 (concluding that Penry claims must fail because [Tennard] made no showing at trial that the criminal act was attributable to his condition).* * Neither ground provided an adequate reason to fail to reach the heart of Tennards Penry claims.
We have never denied that gravity has a place in the relevance analysis, insofar as evidence of a trivial feature of the defendants character or the circumstances of the crime is unlikely to have any tendency to mitigate the defendants culpability. See Skipper , supra, at 7, n. 2 (We do not hold that all facets of the defendants ability to adjust to prison life must be treated as relevant and potentially mitigating. For example, we have no quarrel with the statement … that how often [the defendant] will take a shower is irrelevant to the sentencing determination (quoting State v. Plath , 281 S. C. 1, 15, 313 S. E. 2d 619, 627 (1984)). However, to say that only those features and circumstances that a panel of federal appellate judges deems to be severe (let alone uniquely severe) could have such a tendency is incorrect. Rather, the question is simply whether the evidence is of such a character that it might serve as a basis for a sentence less than death, Skipper , supra, at 5.
The Fifth Circuit was likewise wrong to have refused to consider the debatability of the Penry question on the ground that Tennard had not adduced evidence that his crime was attributable to his low IQ. In Atkins v.   Equally, we cannot countenance the suggestion that low IQ evidence is not relevant mitigating evidenceand thus that the Penry question need not even be askedunless the defendant also establishes a nexus to the crime.
The State claims that the Fifth Circuits Penry I jurisprudence is not at issue in this case. Brief for Respondent 35, n. 21; Tr. of Oral Arg. 33. To the contrary, that jurisprudence is directly at issue because the Fifth Circuit denied Tennard relief on the ground that he did not satisfy the requirements imposed by its constitutional relevance test. As we have explained, the Fifth Circuits screening test has no basis in our precedents and, indeed, is inconsistent with the standard we have adopted for relevance in the capital sentencing context. We therefore hold that the Fifth Circuit assessed Tennards Penry claim under an improper legal standard. Cf. Miller-El v. Cockrell, 537 U. S., at 341 (holding, on certiorari review of the denial of a COA, that the Fifth Circuit had applied an incorrect standard by improperly merging the requirements of two statutory sections).
C
We turn to the analysis the Fifth Circuit should have conducted: Has Tennard demonstrate[d] that reasonable jurists would find the district courts assessment of the constitutional claims debatable or wrong? Slack v. McDaniel , 529 U. S., at 484. We conclude that he has.
Reasonable jurists could conclude that the low IQ evidence Tennard presented was relevant mitigating evidence. Evidence of significantly impaired intellectual functioning is obviously evidence that might serve as a basis for a sentence less than death, Skipper , 476 U. S., at 5; see also, e.g., Wiggins v. Smith, 539 U. S. 510, 535 (2003) (observing, with respect to individual with IQ of 79, that Wiggins[] … diminished mental capacitie[s] further augment his mitigation case); Burger v. Kemp, 483 U. S. 776 n. 7 (1987) (noting that petitioner had an IQ of 82 and functioned at the level of a 12-year-old child, and later that [i]n light of petitioners youth at the time of the offense, … testimony that his mental and emotional development were at a level several years below his chronological age could not have been excluded by the state court (quoting Eddings , 455 U. S., at 116)).
Reasonable jurists also could conclude that the Texas Court of Criminal Appeals application of Penry to the facts of Tennards case was unreasonable. The relationship between the special issues and Tennards low IQ evidence has the same essential features as the relationship between the special issues and Penrys mental retardation evidence. Impaired intellectual functioning has mitigating dimension beyond the impact it has on the individuals ability to act deliberately. See Penry I , 492 U. S., at 322. A reasonable jurist could conclude that the jury might well have given Tennards low IQ evidence aggravating effect in considering his future dangerousness, not only as a matter of probable inference from the evidence but also because the prosecutor told them to do so: [W]hether he has a low IQ or not is not really the issue. Because the legislature, in asking you to address that question, the reasons why he became a danger are not really relevant. The fact that he is a danger, that the evidence shows hes a danger, is the criteria to use in answering that question. App 60. Indeed, the prosecutors comments pressed exactly the most problematic interpretation of the special issues, suggesting that Tennards low IQ was irrelevant in mitigation, but relevant to the question whether he posed a future danger.
* * *
We hold that the Fifth Circuits uniquely severe permanent handicap and nexus tests are incorrect, and we reject them. We hold that reasonable jurists would find debatable or wrong the District Courts disposition of Tennards low-IQ-based Penry claim, and that Tennard is therefore entitled to a certificate of appealability. The judgment of the United States Court of Appeals for the Fifth Circuit is reversed, and the case is remanded for further proceedings consistent with this opinion.
It is so ordered.
* * The Fifth Circuit stated that a majority of the Court of Criminal Appeals found no evidence in this record that [Tennard] is mentally retarded. 284 F. 3d, at 596597. As described above, however, that was the conclusion of a four-judge plurality; the narrowest and thus controlling opinion on this point, correctly described by the Fifth Circuit as conclud[ing] that there was not enough evidence of mental retardation in the record to support Tennards claim, id., at 596, n. 5 (emphasis added), is Judge Meyers concurring opinion.
Opinion
ROBERT JAMES TENNARD, PETITIONER
v.
DOUG
DRETKE, DIRECTOR, TEXAS DEPARTMENT OF
CRIMINAL JUSTICE, CORRECTIONAL
INSTITUTIONS DIVISION
Justice OConnor delivered the opinion of the Court.
In Penry v. Lynaugh, 492 U. S. 302 (1989) (Penry I), we held that the Texas capital sentencing scheme provided a constitutionally inadequate vehicle for jurors to consider and give effect to the mitigating evidence of mental retardation and childhood abuse the petitioner had presented. The petitioner in this case argues that the same scheme was inadequate for jurors to give effect to his evidence of low intelligence. The Texas courts rejected his claim, and a Federal District Court denied his petition for a writ of habeas corpus. We conclude that reasonable jurists would find the district courts assessment of the constitutional claims debatable or wrong, Slack v. McDaniel , 529 U. S. 473, 484 (2000) , and therefore hold that a certificate of appealability should have issued.
I
Petitioner Robert Tennard was convicted by a jury of capital murder in October 1986. The evidence presented at trial indicated that Tennard and two accomplices killed two of his neighbors and robbed their house. Tennard himself stabbed one of the victims to death, and one of the accomplices killed the other victim with a hatchet.
During the penalty phase of the trial, defense counsel called only one witnessTennards parole officerwho testified that Tennards Department of Corrections record from a prior incarceration indicated that he had an IQ of 67. App. 2829. He testified that the IQ test would have been administered as a matter of course. Ibid. The report, which indicated that Tennard was 17 years old at the time it was prepared, was admitted into evidence. On cross-examination, the parole officer testified that he did not know who had administered the test. Id., at 30. The government introduced evidence in the penalty phase regarding a prior conviction for rape, committed when Tennard was 16. The rape victim testified that she had escaped through a window after Tennard permitted her to go to the bathroom to take a bath, promising him she wouldnt run away. Id., at 1617.
The jury was instructed to consider the appropriate punishment by answering the two special issues used at the time in Texas to establish whether a sentence of life imprisonment or death would be imposed:
Was the conduct of the defendant, Robert James Tennard, that caused the death of the deceased committed deliberately and with the reasonable expectation that the death of the deceased or another would result? Id., at 69 (the deliberateness special issue).
Is there a probability that the defendant, Robert James Tennard, would commit criminal acts of violence that would constitute a continuing threat to society? Id., at 70 (the future dangerousness special issue).
  And he believed her. This guy with the 67 IQ, and she goes in and, sure enough, she escapes, just like she should have. That is uncontroverted testimony before you, that we have got a man before us that has got an intelligence quotient . . . that is that low. Id., at 51.
In rebuttal, the prosecution suggested that the low IQ evidence was simply irrelevant to the question of mitigation:
But whether he has a low IQ or not is not really the issue. Because the legislature, in asking you to address that question [the future dangerousness special issue], the reasons why he became a danger are not really relevant. The fact that he is a danger, that the evidence shows hes a danger, is the criteria to use in answering that question. Id., at 60.
The jury answered both special issues in the affirmative, and Tennard was accordingly sentenced to death.
Unsuccessful on direct appeal, Tennard sought state postconviction relief. He argued that, in light of the instructions given to the jury, his death sentence had been obtained in violation of the Eighth Amendment as interpreted by this Court in Penry I . In that case, we had held that it is not enough simply to allow the defendant to present mitigating evidence to the sentencer. The sentencer must also be able to consider and give effect to that evidence in imposing sentence. Penry I , supra, at 319; see also Penry v. Johnson, 532 U. S. 782, 797 (2001) (Penry II) (describing give effect to language of Penry I as the key to that decision). We concluded that the same two special issues that were presented to Tennards jury (plus a third immaterial to the questions now before us) were insufficient for the jury in Penrys case to consider and give effect to Penrys evidence of mental retardation and childhood abuse, and therefore ran afoul of the Eighth Amendment. Penry I , 492 U. S., at 319328. His mental retardation evidence, we held, had relevance to [his] moral culpability beyond the scope of the [deliberateness] special verdict questio[n] because [p]ersonal culpability is not solely a function of a defendants capacity to act deliberately. Id. , at 322 (some brackets in original). Moreover, because the evidence concerning Penrys mental retardation indicated that one effect of his retardation is his inability to learn from his mistakes, his retardation was relevant to the future dangerousness special issue only as an aggravating factor. Id., at 323. As to the evidence of childhood abuse, we held that the two special issues simply failed to provide a vehicle for the jury to give [it] mitigating effect. Id., at 322324.
The Texas Court of Criminal Appeals rejected Tennards Penry claim. Ex parte Tennard , 960 S. W. 2d 57 (1997) (en banc). Writing for a plurality of four, Presiding Judge McCormick observed that the definition of mental retardation adopted in Texas involves three components ((1) subaverage general intellectual functioning; (2) concurrent deficits in adaptive behavior; and (3) onset during the early development period, id., at 60), and concluded: [Tennards] evidence of a low IQ score, standing alone, does not meet this definition. Qualitatively and quantitatively, [Tennards] low IQ evidence does not approach the level of Johnny Paul Penrys evidence of mental retardation… . [W]e find no evidence in this record that applicant is mentally retarded. Id., at 61.
The plurality went on to consider whether Tennard would be entitled to relief under Penry even if his low IQ fell within Penry s definition of mental retardation. 960 S. W. 2d, at 61. It held that he would not. The court explained that, unlike the evidence presented in Penrys case, there is no evidence … [that Tennards] low IQ rendered him unable to appreciate the wrongfulness of his conduct when he committed the offense, or that his low IQ rendered him unable to learn from his mistakes … or control his impulses … . Id., at 62. It found there was no danger that the jury would have given the evidence only aggravating effect in answering the future dangerousness special issue, and that the low IQ and gullibility evidence was not beyond the jurys effective reach because the jury could have used this evidence for a no answer to the deliberateness special issue. Ibid.
Two judges concurred separately, and wrote that this Court has sustained a Penry claim only when there is evidence of mental retardation. But even in those cases, the evidence of mental retardation was always something more than what was presented in this case. 960 S. W. 2d, at 64 (opinion of Meyers, J.) (citations omitted). Taking a more permissive view of evidence of impaired intellectual functioning than did the plurality ([F]or Penry purposes, courts should not distinguish between mental retardation and dementia, even though the onset of the latter may occur after age eighteen, id., at 65), the concurring judges nevertheless concluded that the record does not contain sufficient evidence to support Tennards Penry claim. 960 S. W. 2d , at 63. The concurring judges also rejected Tennards contention that evidence of an IQ of below 70 alone requires a Penry instruction because published opinions of the Texas courts had uniformly required more. Id., at 67.
Judge Baird dissented, maintaining that the Court of Criminal Appeals had consistent[ly] held, in the wake of Penry I , that evidence of mental retardation cannot be adequately considered within the statutory special issues. 960 S. W. 2d, at 67. The court had strayed from its precedent, Judge Baird wrote, and instead of asking simply whether the jury had a vehicle for considering the mitigating evidence, had weigh[ed] the sufficiency of [Tennards] mitigating evidence. Id., at 70. Judges Overstreet and Womack dissented without opinion. Id., at 63.
Tennard sought federal habeas corpus relief. The District Court denied his petition. Tennard v. Johnson, Civ. Action No. H984238 (S D Tex., July 25, 2000), App. 121. The court began by observing that [e]vidence of a single low score on an unidentified intelligence test is not evidence that Tennard was mentally retarded. Id., at 128. It then considered whether the 67 IQ score was within the effective reach of the jury. Ibid. Noting that Tennards low IQ score was not concealed from the jury; it was in evidence, and both sides argued its significance for punishment, the court concluded that the jury had adequate means, in the two special issues, by which to give effect to that mitigating evidence. Id., at 129. The court subsequently denied Tennard a certificate of appealability (COA). Civ. Action No. H984238 (S D Tex. Oct. 17, 2000), see App. 2.
The Court of Appeals for the Fifth Circuit, after full briefing and oral argument, issued an opinion holding that Tennard was not entitled to a COA because his Penry claim was not debatable among jurists of reason. Tennard v. Cockrell, 284 F. 3d 591 (2002). The court began by stating the test applied in the Fifth Circuit to Penry claims, which involves a threshold inquiry into whether the petitioner presented constitutionally relevant mitigating evidence, that is, evidence of a uniquely severe permanent handicap with which the defendant was burdened through no fault of his own, and evidence that the criminal act was attributable to this severe permanent condition. 284 F. 3d, at 595.
The court then held that Tennard was not entitled to a COA, for two reasons: First, it held that evidence of low IQ alone does not constitute a uniquely severe condition, and rejected Tennards claim that his evidence was of mental retardation, not just low IQ, because no evidence had been introduced tying his IQ score to retardation. Id., at 596. Second, it held that even if Tennards evidence was mental retardation evidence, his claim must fail because he did not show that the crime he committed was attributable to his low IQ. Id., at 596597. Judge Dennis dissented, concluding that the Texas courts application of Penry was unreasonable and that Tennard was entitled to habeas relief. 284 F. 3d, at 597604.
Tennard filed a petition for certiorari, and this Court granted the writ, vacated the judgment, and remanded for further consideration in light of Atkins v. Virginia, 536 U. S. 304 (2002) . Tennard v. Cockrell, 537 U. S. 802 (2002) . The Fifth Circuit took the remand to be for consideration of a substantive Atkins claim. It observed that Tennard has never argued that the Eighth Amendment prohibits his execution and reinstated its prior panel opinion. 317 F. 3d 476, 477 (2003). We again granted certiorari. 540 U. S. 945 (2003) .
II
A
A COA should issue if the applicant has made a substantial showing of the denial of a constitutional right, 28 U. S. C. §2253(c)(2), which we have interpreted to require that the petitioner must demonstrate that reasonable jurists would find the district courts assessment of the constitutional claims debatable or wrong. Slack v. McDaniel , 529 U. S., at 484; see also Miller-El v. Cockrell, 537 U. S. 322, 336 (2003) (Under the controlling standard, a petitioner must sho[w] that reasonable jurists could debate whether (or, for that matter, agree that) the petition should have been resolved in a different manner or that the issues presented were adequate to deserve encouragement to proceed further ). The petitioners arguments ultimately must be assessed under the deferential standard required by 28 U. S. C. §2254(d)(1): Relief may not be granted unless the state court adjudication resulted in a decision that was contrary to, or involved an unreasonable application of, clearly established Federal law, as determined by the Supreme Court of the United States.
The State has never disputed that Tennards Penry claim was properly preserved for federal habeas review. Not only did the state court consider the question on the merits, we note that the issue was also raised by defense counsel prior to trial in a motion to set aside the indictment on the ground, among others, that the Texas capital murder statutes do not explicitly allow the consideration of any specific mitigating circumstances at the punishment phase of the prosecution and, consequently, are violative of the accuseds right to be free from cruel and unusual punishment and are also void for vagueness. Defendants Motion to Set Aside the Indictment, in Cause No. 431127 (248th Jud. Dist. Ct. Harris County, Tex., May 28, 1986), p. 4.
B
Despite paying lipservice to the principles guiding issuance of a COA, Tennard v. Cockrell, supra, at 594, the Fifth Circuits analysis proceeded along a distinctly different track. Rather than examining the District Courts analysis of the Texas court decision, it invoked its own restrictive gloss on Penry I:
In reviewing a Penry claim, we must determine whether the mitigating evidence introduced at trial was constitutionally relevant and beyond the effective reach of the jury. … To be constitutionally relevant, the evidence must show (1) a uniquely severe permanent handicap with which the defendant was burdened through no fault of his own, … and (2) that the criminal act was attributable to this severe permanent condition. 284 F. 3d, at 595 (quoting Davis v. Scott, 51 F. 3d, 457, 460461 (CA5 1998)).
This test for constitutional relevance, characterized by the State at oral argument as a threshold screening test, Tr. of Oral Arg.10, 28, appears to be applied uniformly in the Fifth Circuit to Penry claims. See, e.g., Bigby v. Cockrell , 340 F. 3d 259, 273 (2003); Robertson v. Cockrell , 325 F. 3d 243, 251 (2003) (en banc); Smith v. Cockrell , 311 F. 3d 661, 680 (2002); Blue v. Cockrell , 298 F. 3d 318, 320321 (2002); Davis v. Scott , 51 F. 3d 457, 460461 (1995). Only after the court finds that certain mitigating evidence is constitutionally relevant will it consider whether that evidence was within the effective reach of the jur[y]. E.g., Smith, supra, at 680 (court asks whether evidence was constitutionally relevant and, if so, will consider whether it was within jurys effective reach). In the decision below, the Fifth Circuit concluded that Tennard was precluded from establishing a Penry claim because his low IQ evidence bore no nexus to the crime, and so did not move on to the effective reach question. 284 F. 3d, at 597.
The Fifth Circuits test has no foundation in the decisions of this Court. Neither Penry I nor its progeny screened mitigating evidence for constitutional relevance before considering whether the jury instructions comported with the Eighth Amendment. Indeed, the mitigating evidence presented in Penry I was concededly relevant, see Tr. of Oral Arg., O. T. 1988, No. 876177, pp. 3436, so even if limiting principles regarding relevance were suggested in our opinionand we do not think they werethey could not have been material to the holding.
When we addressed directly the relevance standard applicable to mitigating evidence in capital cases in McKoy v. North Carolina, 494 U. S. 433, 440441 (1990) , we spoke in the most expansive terms. We established that the meaning of relevance is no different in the context of mitigating evidence introduced in a capital sentencing proceeding than in any other context, and thus the general evidentiary standard any tendency to make the existence of any fact that is of consequence to the determination of the action more probable or less probable than it would be without the evidence applies. Id., at 440 (quoting New Jersey v. T. L. O., 469 U. S. 325, 345 (1985) ). We quoted approvingly from a dissenting opinion in the state court: Relevant mitigating evidence is evidence which tends logically to prove or disprove some fact or circumstance which a fact-finder could reasonably deem to have mitigating value. 494 U. S., at 440 (quoting State v. McKoy , 323 N. C. 1, 5556, 372 S. E. 2d, 12, 45 (1988) (opinion of Exum, C. J.)). Thus, a State cannot bar the consideration of … evidence if the sentencer could reasonably find that it warrants a sentence less than death. 494 U. S., at 441.
Once this low threshold for relevance is met, the Eighth Amendment requires that the jury be able to consider and give effect to a capital defendants mitigating evidence. Boyde v. California, 494 U. S. 370, 377378 (1990) (citing Lockett v. Ohio, 438 U. S. 586 (1978) ; Eddings v. Oklahoma, 455 U. S. 104 (1982) ; Penry I, 492 U. S. 302 (1989) ); see also Payne v. Tennessee, 501 U. S. 808, 822 (1991) (We have held that a State cannot preclude the sentencer from considering any relevant mitigating evidence that the defendant proffers in support of a sentence less than death… . [V]irtually no limits are placed on the relevant mitigating evidence a capital defendant may introduce concerning his own circumstances (quoting Eddings , supra , at 114)).
The Fifth Circuits test is inconsistent with these principles. Most obviously, the test will screen out any positive aspect of a defendants character, because good character traits are neither handicap[s] nor typically traits to which criminal activity is attributable. In Skipper v. South Carolina, 476 U. S. 1, 5 (1986) , however, we made clear that good-character evidence can be evidence that, [u]nder Eddings , … may not be excluded from the sentencers consideration. We observed that even though the petitioners evidence of good conduct in jail did not relate specifically to petitioners culpability for the crime he committed, there is no question but that such [evidence] … would be mitigating in the sense that [it] might serve as a basis for a sentence less than death. Lockett , supra , at 604 id., at 45 (citation omitted). Such evidence, we said, of a defendants disposition to make a well-behaved and peaceful adjustment to life in prison is … by its nature relevant to the sentencing determination. Id., at 7. Of course, the Texas courts might reasonably conclude that evidence of good conduct in jail was within the jurys effective reach via the future dangerousness special issue. See Franklin v. Lynaugh, 487 U. S. 164, 177178 (1988) (plurality opinion); id., at 185186 ( OConnor, J. , concurring in judgment). But under the Fifth Circuits test, the evidence would have been screened out before the time came to consider that question.
In Tennards case, the Fifth Circuit invoked both the uniquely severe and the nexus elements of its test to deny him relief under Penry I . Tennard v. Cockrell, 284 F. 3d, at 596 (contrasting Tennards low IQ evidence, which did not constitute a uniquely severe condition, with mental retardation, a severe permanent condition); id., at 596597 (concluding that Penry claims must fail because [Tennard] made no showing at trial that the criminal act was attributable to his condition).* * Neither ground provided an adequate reason to fail to reach the heart of Tennards Penry claims.
We have never denied that gravity has a place in the relevance analysis, insofar as evidence of a trivial feature of the defendants character or the circumstances of the crime is unlikely to have any tendency to mitigate the defendants culpability. See Skipper , supra, at 7, n. 2 (We do not hold that all facets of the defendants ability to adjust to prison life must be treated as relevant and potentially mitigating. For example, we have no quarrel with the statement … that how often [the defendant] will take a shower is irrelevant to the sentencing determination (quoting State v. Plath , 281 S. C. 1, 15, 313 S. E. 2d 619, 627 (1984)). However, to say that only those features and circumstances that a panel of federal appellate judges deems to be severe (let alone uniquely severe) could have such a tendency is incorrect. Rather, the question is simply whether the evidence is of such a character that it might serve as a basis for a sentence less than death, Skipper , supra, at 5.
The Fifth Circuit was likewise wrong to have refused to consider the debatability of the Penry question on the ground that Tennard had not adduced evidence that his crime was attributable to his low IQ. In Atkins v.   Equally, we cannot countenance the suggestion that low IQ evidence is not relevant mitigating evidenceand thus that the Penry question need not even be askedunless the defendant also establishes a nexus to the crime.
The State claims that the Fifth Circuits Penry I jurisprudence is not at issue in this case. Brief for Respondent 35, n. 21; Tr. of Oral Arg. 33. To the contrary, that jurisprudence is directly at issue because the Fifth Circuit denied Tennard relief on the ground that he did not satisfy the requirements imposed by its constitutional relevance test. As we have explained, the Fifth Circuits screening test has no basis in our precedents and, indeed, is inconsistent with the standard we have adopted for relevance in the capital sentencing context. We therefore hold that the Fifth Circuit assessed Tennards Penry claim under an improper legal standard. Cf. Miller-El v. Cockrell, 537 U. S., at 341 (holding, on certiorari review of the denial of a COA, that the Fifth Circuit had applied an incorrect standard by improperly merging the requirements of two statutory sections).
C
We turn to the analysis the Fifth Circuit should have conducted: Has Tennard demonstrate[d] that reasonable jurists would find the district courts assessment of the constitutional claims debatable or wrong? Slack v. McDaniel , 529 U. S., at 484. We conclude that he has.
Reasonable jurists could conclude that the low IQ evidence Tennard presented was relevant mitigating evidence. Evidence of significantly impaired intellectual functioning is obviously evidence that might serve as a basis for a sentence less than death, Skipper , 476 U. S., at 5; see also, e.g., Wiggins v. Smith, 539 U. S. 510, 535 (2003) (observing, with respect to individual with IQ of 79, that Wiggins[] … diminished mental capacitie[s] further augment his mitigation case); Burger v. Kemp, 483 U. S. 776 n. 7 (1987) (noting that petitioner had an IQ of 82 and functioned at the level of a 12-year-old child, and later that [i]n light of petitioners youth at the time of the offense, … testimony that his mental and emotional development were at a level several years below his chronological age could not have been excluded by the state court (quoting Eddings , 455 U. S., at 116)).
Reasonable jurists also could conclude that the Texas Court of Criminal Appeals application of Penry to the facts of Tennards case was unreasonable. The relationship between the special issues and Tennards low IQ evidence has the same essential features as the relationship between the special issues and Penrys mental retardation evidence. Impaired intellectual functioning has mitigating dimension beyond the impact it has on the individuals ability to act deliberately. See Penry I , 492 U. S., at 322. A reasonable jurist could conclude that the jury might well have given Tennards low IQ evidence aggravating effect in considering his future dangerousness, not only as a matter of probable inference from the evidence but also because the prosecutor told them to do so: [W]hether he has a low IQ or not is not really the issue. Because the legislature, in asking you to address that question, the reasons why he became a danger are not really relevant. The fact that he is a danger, that the evidence shows hes a danger, is the criteria to use in answering that question. App 60. Indeed, the prosecutors comments pressed exactly the most problematic interpretation of the special issues, suggesting that Tennards low IQ was irrelevant in mitigation, but relevant to the question whether he posed a future danger.
* * *
We hold that the Fifth Circuits uniquely severe permanent handicap and nexus tests are incorrect, and we reject them. We hold that reasonable jurists would find debatable or wrong the District Courts disposition of Tennards low-IQ-based Penry claim, and that Tennard is therefore entitled to a certificate of appealability. The judgment of the United States Court of Appeals for the Fifth Circuit is reversed, and the case is remanded for further proceedings consistent with this opinion.
It is so ordered.
* * The Fifth Circuit stated that a majority of the Court of Criminal Appeals found no evidence in this record that [Tennard] is mentally retarded. 284 F. 3d, at 596597. As described above, however, that was the conclusion of a four-judge plurality; the narrowest and thus controlling opinion on this point, correctly described by the Fifth Circuit as conclud[ing] that there was not enough evidence of mental retardation in the record to support Tennards claim, id., at 596, n. 5 (emphasis added), is Judge Meyers concurring opinion.
Opinion
ROBERT JAMES TENNARD, PETITIONER
v.
DOUG
DRETKE, DIRECTOR, TEXAS DEPARTMENT OF
CRIMINAL JUSTICE, CORRECTIONAL
INSTITUTIONS DIVISION
Justice OConnor delivered the opinion of the Court.
In Penry v. Lynaugh, 492 U. S. 302 (1989) (Penry I), we held that the Texas capital sentencing scheme provided a constitutionally inadequate vehicle for jurors to consider and give effect to the mitigating evidence of mental retardation and childhood abuse the petitioner had presented. The petitioner in this case argues that the same scheme was inadequate for jurors to give effect to his evidence of low intelligence. The Texas courts rejected his claim, and a Federal District Court denied his petition for a writ of habeas corpus. We conclude that reasonable jurists would find the district courts assessment of the constitutional claims debatable or wrong, Slack v. McDaniel , 529 U. S. 473, 484 (2000) , and therefore hold that a certificate of appealability should have issued.
I
Petitioner Robert Tennard was convicted by a jury of capital murder in October 1986. The evidence presented at trial indicated that Tennard and two accomplices killed two of his neighbors and robbed their house. Tennard himself stabbed one of the victims to death, and one of the accomplices killed the other victim with a hatchet.
During the penalty phase of the trial, defense counsel called only one witnessTennards parole officerwho testified that Tennards Department of Corrections record from a prior incarceration indicated that he had an IQ of 67. App. 2829. He testified that the IQ test would have been administered as a matter of course. Ibid. The report, which indicated that Tennard was 17 years old at the time it was prepared, was admitted into evidence. On cross-examination, the parole officer testified that he did not know who had administered the test. Id., at 30. The government introduced evidence in the penalty phase regarding a prior conviction for rape, committed when Tennard was 16. The rape victim testified that she had escaped through a window after Tennard permitted her to go to the bathroom to take a bath, promising him she wouldnt run away. Id., at 1617.
The jury was instructed to consider the appropriate punishment by answering the two special issues used at the time in Texas to establish whether a sentence of life imprisonment or death would be imposed:
Was the conduct of the defendant, Robert James Tennard, that caused the death of the deceased committed deliberately and with the reasonable expectation that the death of the deceased or another would result? Id., at 69 (the deliberateness special issue).
Is there a probability that the defendant, Robert James Tennard, would commit criminal acts of violence that would constitute a continuing threat to society? Id., at 70 (the future dangerousness special issue).
  And he believed her. This guy with the 67 IQ, and she goes in and, sure enough, she escapes, just like she should have. That is uncontroverted testimony before you, that we have got a man before us that has got an intelligence quotient . . . that is that low. Id., at 51.
In rebuttal, the prosecution suggested that the low IQ evidence was simply irrelevant to the question of mitigation:
But whether he has a low IQ or not is not really the issue. Because the legislature, in asking you to address that question [the future dangerousness special issue], the reasons why he became a danger are not really relevant. The fact that he is a danger, that the evidence shows hes a danger, is the criteria to use in answering that question. Id., at 60.
The jury answered both special issues in the affirmative, and Tennard was accordingly sentenced to death.
Unsuccessful on direct appeal, Tennard sought state postconviction relief. He argued that, in light of the instructions given to the jury, his death sentence had been obtained in violation of the Eighth Amendment as interpreted by this Court in Penry I . In that case, we had held that it is not enough simply to allow the defendant to present mitigating evidence to the sentencer. The sentencer must also be able to consider and give effect to that evidence in imposing sentence. Penry I , supra, at 319; see also Penry v. Johnson, 532 U. S. 782, 797 (2001) (Penry II) (describing give effect to language of Penry I as the key to that decision). We concluded that the same two special issues that were presented to Tennards jury (plus a third immaterial to the questions now before us) were insufficient for the jury in Penrys case to consider and give effect to Penrys evidence of mental retardation and childhood abuse, and therefore ran afoul of the Eighth Amendment. Penry I , 492 U. S., at 319328. His mental retardation evidence, we held, had relevance to [his] moral culpability beyond the scope of the [deliberateness] special verdict questio[n] because [p]ersonal culpability is not solely a function of a defendants capacity to act deliberately. Id. , at 322 (some brackets in original). Moreover, because the evidence concerning Penrys mental retardation indicated that one effect of his retardation is his inability to learn from his mistakes, his retardation was relevant to the future dangerousness special issue only as an aggravating factor. Id., at 323. As to the evidence of childhood abuse, we held that the two special issues simply failed to provide a vehicle for the jury to give [it] mitigating effect. Id., at 322324.
The Texas Court of Criminal Appeals rejected Tennards Penry claim. Ex parte Tennard , 960 S. W. 2d 57 (1997) (en banc). Writing for a plurality of four, Presiding Judge McCormick observed that the definition of mental retardation adopted in Texas involves three components ((1) subaverage general intellectual functioning; (2) concurrent deficits in adaptive behavior; and (3) onset during the early development period, id., at 60), and concluded: [Tennards] evidence of a low IQ score, standing alone, does not meet this definition. Qualitatively and quantitatively, [Tennards] low IQ evidence does not approach the level of Johnny Paul Penrys evidence of mental retardation… . [W]e find no evidence in this record that applicant is mentally retarded. Id., at 61.
The plurality went on to consider whether Tennard would be entitled to relief under Penry even if his low IQ fell within Penry s definition of mental retardation. 960 S. W. 2d, at 61. It held that he would not. The court explained that, unlike the evidence presented in Penrys case, there is no evidence … [that Tennards] low IQ rendered him unable to appreciate the wrongfulness of his conduct when he committed the offense, or that his low IQ rendered him unable to learn from his mistakes … or control his impulses … . Id., at 62. It found there was no danger that the jury would have given the evidence only aggravating effect in answering the future dangerousness special issue, and that the low IQ and gullibility evidence was not beyond the jurys effective reach because the jury could have used this evidence for a no answer to the deliberateness special issue. Ibid.
Two judges concurred separately, and wrote that this Court has sustained a Penry claim only when there is evidence of mental retardation. But even in those cases, the evidence of mental retardation was always something more than what was presented in this case. 960 S. W. 2d, at 64 (opinion of Meyers, J.) (citations omitted). Taking a more permissive view of evidence of impaired intellectual functioning than did the plurality ([F]or Penry purposes, courts should not distinguish between mental retardation and dementia, even though the onset of the latter may occur after age eighteen, id., at 65), the concurring judges nevertheless concluded that the record does not contain sufficient evidence to support Tennards Penry claim. 960 S. W. 2d , at 63. The concurring judges also rejected Tennards contention that evidence of an IQ of below 70 alone requires a Penry instruction because published opinions of the Texas courts had uniformly required more. Id., at 67.
Judge Baird dissented, maintaining that the Court of Criminal Appeals had consistent[ly] held, in the wake of Penry I , that evidence of mental retardation cannot be adequately considered within the statutory special issues. 960 S. W. 2d, at 67. The court had strayed from its precedent, Judge Baird wrote, and instead of asking simply whether the jury had a vehicle for considering the mitigating evidence, had weigh[ed] the sufficiency of [Tennards] mitigating evidence. Id., at 70. Judges Overstreet and Womack dissented without opinion. Id., at 63.
Tennard sought federal habeas corpus relief. The District Court denied his petition. Tennard v. Johnson, Civ. Action No. H984238 (S D Tex., July 25, 2000), App. 121. The court began by observing that [e]vidence of a single low score on an unidentified intelligence test is not evidence that Tennard was mentally retarded. Id., at 128. It then considered whether the 67 IQ score was within the effective reach of the jury. Ibid. Noting that Tennards low IQ score was not concealed from the jury; it was in evidence, and both sides argued its significance for punishment, the court concluded that the jury had adequate means, in the two special issues, by which to give effect to that mitigating evidence. Id., at 129. The court subsequently denied Tennard a certificate of appealability (COA). Civ. Action No. H984238 (S D Tex. Oct. 17, 2000), see App. 2.
The Court of Appeals for the Fifth Circuit, after full briefing and oral argument, issued an opinion holding that Tennard was not entitled to a COA because his Penry claim was not debatable among jurists of reason. Tennard v. Cockrell, 284 F. 3d 591 (2002). The court began by stating the test applied in the Fifth Circuit to Penry claims, which involves a threshold inquiry into whether the petitioner presented constitutionally relevant mitigating evidence, that is, evidence of a uniquely severe permanent handicap with which the defendant was burdened through no fault of his own, and evidence that the criminal act was attributable to this severe permanent condition. 284 F. 3d, at 595.
The court then held that Tennard was not entitled to a COA, for two reasons: First, it held that evidence of low IQ alone does not constitute a uniquely severe condition, and rejected Tennards claim that his evidence was of mental retardation, not just low IQ, because no evidence had been introduced tying his IQ score to retardation. Id., at 596. Second, it held that even if Tennards evidence was mental retardation evidence, his claim must fail because he did not show that the crime he committed was attributable to his low IQ. Id., at 596597. Judge Dennis dissented, concluding that the Texas courts application of Penry was unreasonable and that Tennard was entitled to habeas relief. 284 F. 3d, at 597604.
Tennard filed a petition for certiorari, and this Court granted the writ, vacated the judgment, and remanded for further consideration in light of Atkins v. Virginia, 536 U. S. 304 (2002) . Tennard v. Cockrell, 537 U. S. 802 (2002) . The Fifth Circuit took the remand to be for consideration of a substantive Atkins claim. It observed that Tennard has never argued that the Eighth Amendment prohibits his execution and reinstated its prior panel opinion. 317 F. 3d 476, 477 (2003). We again granted certiorari. 540 U. S. 945 (2003) .
II
A
A COA should issue if the applicant has made a substantial showing of the denial of a constitutional right, 28 U. S. C. §2253(c)(2), which we have interpreted to require that the petitioner must demonstrate that reasonable jurists would find the district courts assessment of the constitutional claims debatable or wrong. Slack v. McDaniel , 529 U. S., at 484; see also Miller-El v. Cockrell, 537 U. S. 322, 336 (2003) (Under the controlling standard, a petitioner must sho[w] that reasonable jurists could debate whether (or, for that matter, agree that) the petition should have been resolved in a different manner or that the issues presented were adequate to deserve encouragement to proceed further ). The petitioners arguments ultimately must be assessed under the deferential standard required by 28 U. S. C. §2254(d)(1): Relief may not be granted unless the state court adjudication resulted in a decision that was contrary to, or involved an unreasonable application of, clearly established Federal law, as determined by the Supreme Court of the United States.
The State has never disputed that Tennards Penry claim was properly preserved for federal habeas review. Not only did the state court consider the question on the merits, we note that the issue was also raised by defense counsel prior to trial in a motion to set aside the indictment on the ground, among others, that the Texas capital murder statutes do not explicitly allow the consideration of any specific mitigating circumstances at the punishment phase of the prosecution and, consequently, are violative of the accuseds right to be free from cruel and unusual punishment and are also void for vagueness. Defendants Motion to Set Aside the Indictment, in Cause No. 431127 (248th Jud. Dist. Ct. Harris County, Tex., May 28, 1986), p. 4.
B
Despite paying lipservice to the principles guiding issuance of a COA, Tennard v. Cockrell, supra, at 594, the Fifth Circuits analysis proceeded along a distinctly different track. Rather than examining the District Courts analysis of the Texas court decision, it invoked its own restrictive gloss on Penry I:
In reviewing a Penry claim, we must determine whether the mitigating evidence introduced at trial was constitutionally relevant and beyond the effective reach of the jury. … To be constitutionally relevant, the evidence must show (1) a uniquely severe permanent handicap with which the defendant was burdened through no fault of his own, … and (2) that the criminal act was attributable to this severe permanent condition. 284 F. 3d, at 595 (quoting Davis v. Scott, 51 F. 3d, 457, 460461 (CA5 1998)).
This test for constitutional relevance, characterized by the State at oral argument as a threshold screening test, Tr. of Oral Arg.10, 28, appears to be applied uniformly in the Fifth Circuit to Penry claims. See, e.g., Bigby v. Cockrell , 340 F. 3d 259, 273 (2003); Robertson v. Cockrell , 325 F. 3d 243, 251 (2003) (en banc); Smith v. Cockrell , 311 F. 3d 661, 680 (2002); Blue v. Cockrell , 298 F. 3d 318, 320321 (2002); Davis v. Scott , 51 F. 3d 457, 460461 (1995). Only after the court finds that certain mitigating evidence is constitutionally relevant will it consider whether that evidence was within the effective reach of the jur[y]. E.g., Smith, supra, at 680 (court asks whether evidence was constitutionally relevant and, if so, will consider whether it was within jurys effective reach). In the decision below, the Fifth Circuit concluded that Tennard was precluded from establishing a Penry claim because his low IQ evidence bore no nexus to the crime, and so did not move on to the effective reach question. 284 F. 3d, at 597.
The Fifth Circuits test has no foundation in the decisions of this Court. Neither Penry I nor its progeny screened mitigating evidence for constitutional relevance before considering whether the jury instructions comported with the Eighth Amendment. Indeed, the mitigating evidence presented in Penry I was concededly relevant, see Tr. of Oral Arg., O. T. 1988, No. 876177, pp. 3436, so even if limiting principles regarding relevance were suggested in our opinionand we do not think they werethey could not have been material to the holding.
When we addressed directly the relevance standard applicable to mitigating evidence in capital cases in McKoy v. North Carolina, 494 U. S. 433, 440441 (1990) , we spoke in the most expansive terms. We established that the meaning of relevance is no different in the context of mitigating evidence introduced in a capital sentencing proceeding than in any other context, and thus the general evidentiary standard any tendency to make the existence of any fact that is of consequence to the determination of the action more probable or less probable than it would be without the evidence applies. Id., at 440 (quoting New Jersey v. T. L. O., 469 U. S. 325, 345 (1985) ). We quoted approvingly from a dissenting opinion in the state court: Relevant mitigating evidence is evidence which tends logically to prove or disprove some fact or circumstance which a fact-finder could reasonably deem to have mitigating value. 494 U. S., at 440 (quoting State v. McKoy , 323 N. C. 1, 5556, 372 S. E. 2d, 12, 45 (1988) (opinion of Exum, C. J.)). Thus, a State cannot bar the consideration of … evidence if the sentencer could reasonably find that it warrants a sentence less than death. 494 U. S., at 441.
Once this low threshold for relevance is met, the Eighth Amendment requires that the jury be able to consider and give effect to a capital defendants mitigating evidence. Boyde v. California, 494 U. S. 370, 377378 (1990) (citing Lockett v. Ohio, 438 U. S. 586 (1978) ; Eddings v. Oklahoma, 455 U. S. 104 (1982) ; Penry I, 492 U. S. 302 (1989) ); see also Payne v. Tennessee, 501 U. S. 808, 822 (1991) (We have held that a State cannot preclude the sentencer from considering any relevant mitigating evidence that the defendant proffers in support of a sentence less than death… . [V]irtually no limits are placed on the relevant mitigating evidence a capital defendant may introduce concerning his own circumstances (quoting Eddings , supra , at 114)).
The Fifth Circuits test is inconsistent with these principles. Most obviously, the test will screen out any positive aspect of a defendants character, because good character traits are neither handicap[s] nor typically traits to which criminal activity is attributable. In Skipper v. South Carolina, 476 U. S. 1, 5 (1986) , however, we made clear that good-character evidence can be evidence that, [u]nder Eddings , … may not be excluded from the sentencers consideration. We observed that even though the petitioners evidence of good conduct in jail did not relate specifically to petitioners culpability for the crime he committed, there is no question but that such [evidence] … would be mitigating in the sense that [it] might serve as a basis for a sentence less than death. Lockett , supra , at 604 id., at 45 (citation omitted). Such evidence, we said, of a defendants disposition to make a well-behaved and peaceful adjustment to life in prison is … by its nature relevant to the sentencing determination. Id., at 7. Of course, the Texas courts might reasonably conclude that evidence of good conduct in jail was within the jurys effective reach via the future dangerousness special issue. See Franklin v. Lynaugh, 487 U. S. 164, 177178 (1988) (plurality opinion); id., at 185186 ( OConnor, J. , concurring in judgment). But under the Fifth Circuits test, the evidence would have been screened out before the time came to consider that question.
In Tennards case, the Fifth Circuit invoked both the uniquely severe and the nexus elements of its test to deny him relief under Penry I . Tennard v. Cockrell, 284 F. 3d, at 596 (contrasting Tennards low IQ evidence, which did not constitute a uniquely severe condition, with mental retardation, a severe permanent condition); id., at 596597 (concluding that Penry claims must fail because [Tennard] made no showing at trial that the criminal act was attributable to his condition).* * Neither ground provided an adequate reason to fail to reach the heart of Tennards Penry claims.
We have never denied that gravity has a place in the relevance analysis, insofar as evidence of a trivial feature of the defendants character or the circumstances of the crime is unlikely to have any tendency to mitigate the defendants culpability. See Skipper , supra, at 7, n. 2 (We do not hold that all facets of the defendants ability to adjust to prison life must be treated as relevant and potentially mitigating. For example, we have no quarrel with the statement … that how often [the defendant] will take a shower is irrelevant to the sentencing determination (quoting State v. Plath , 281 S. C. 1, 15, 313 S. E. 2d 619, 627 (1984)). However, to say that only those features and circumstances that a panel of federal appellate judges deems to be severe (let alone uniquely severe) could have such a tendency is incorrect. Rather, the question is simply whether the evidence is of such a character that it might serve as a basis for a sentence less than death, Skipper , supra, at 5.
The Fifth Circuit was likewise wrong to have refused to consider the debatability of the Penry question on the ground that Tennard had not adduced evidence that his crime was attributable to his low IQ. In Atkins v.   Equally, we cannot countenance the suggestion that low IQ evidence is not relevant mitigating evidenceand thus that the Penry question need not even be askedunless the defendant also establishes a nexus to the crime.
The State claims that the Fifth Circuits Penry I jurisprudence is not at issue in this case. Brief for Respondent 35, n. 21; Tr. of Oral Arg. 33. To the contrary, that jurisprudence is directly at issue because the Fifth Circuit denied Tennard relief on the ground that he did not satisfy the requirements imposed by its constitutional relevance test. As we have explained, the Fifth Circuits screening test has no basis in our precedents and, indeed, is inconsistent with the standard we have adopted for relevance in the capital sentencing context. We therefore hold that the Fifth Circuit assessed Tennards Penry claim under an improper legal standard. Cf. Miller-El v. Cockrell, 537 U. S., at 341 (holding, on certiorari review of the denial of a COA, that the Fifth Circuit had applied an incorrect standard by improperly merging the requirements of two statutory sections).
C
We turn to the analysis the Fifth Circuit should have conducted: Has Tennard demonstrate[d] that reasonable jurists would find the district courts assessment of the constitutional claims debatable or wrong? Slack v. McDaniel , 529 U. S., at 484. We conclude that he has.
Reasonable jurists could conclude that the low IQ evidence Tennard presented was relevant mitigating evidence. Evidence of significantly impaired intellectual functioning is obviously evidence that might serve as a basis for a sentence less than death, Skipper , 476 U. S., at 5; see also, e.g., Wiggins v. Smith, 539 U. S. 510, 535 (2003) (observing, with respect to individual with IQ of 79, that Wiggins[] … diminished mental capacitie[s] further augment his mitigation case); Burger v. Kemp, 483 U. S. 776 n. 7 (1987) (noting that petitioner had an IQ of 82 and functioned at the level of a 12-year-old child, and later that [i]n light of petitioners youth at the time of the offense, … testimony that his mental and emotional development were at a level several years below his chronological age could not have been excluded by the state court (quoting Eddings , 455 U. S., at 116)).
Reasonable jurists also could conclude that the Texas Court of Criminal Appeals application of Penry to the facts of Tennards case was unreasonable. The relationship between the special issues and Tennards low IQ evidence has the same essential features as the relationship between the special issues and Penrys mental retardation evidence. Impaired intellectual functioning has mitigating dimension beyond the impact it has on the individuals ability to act deliberately. See Penry I , 492 U. S., at 322. A reasonable jurist could conclude that the jury might well have given Tennards low IQ evidence aggravating effect in considering his future dangerousness, not only as a matter of probable inference from the evidence but also because the prosecutor told them to do so: [W]hether he has a low IQ or not is not really the issue. Because the legislature, in asking you to address that question, the reasons why he became a danger are not really relevant. The fact that he is a danger, that the evidence shows hes a danger, is the criteria to use in answering that question. App 60. Indeed, the prosecutors comments pressed exactly the most problematic interpretation of the special issues, suggesting that Tennards low IQ was irrelevant in mitigation, but relevant to the question whether he posed a future danger.
* * *
We hold that the Fifth Circuits uniquely severe permanent handicap and nexus tests are incorrect, and we reject them. We hold that reasonable jurists would find debatable or wrong the District Courts disposition of Tennards low-IQ-based Penry claim, and that Tennard is therefore entitled to a certificate of appealability. The judgment of the United States Court of Appeals for the Fifth Circuit is reversed, and the case is remanded for further proceedings consistent with this opinion.
It is so ordered.
* * The Fifth Circuit stated that a majority of the Court of Criminal Appeals found no evidence in this record that [Tennard] is mentally retarded. 284 F. 3d, at 596597. As described above, however, that was the conclusion of a four-judge plurality; the narrowest and thus controlling opinion on this point, correctly described by the Fifth Circuit as conclud[ing] that there was not enough evidence of mental retardation in the record to support Tennards claim, id., at 596, n. 5 (emphasis added), is Judge Meyers concurring opinion.
Opinion
ROBERT JAMES TENNARD, PETITIONER
v.
DOUG
DRETKE, DIRECTOR, TEXAS DEPARTMENT OF
CRIMINAL JUSTICE, CORRECTIONAL
INSTITUTIONS DIVISION
Justice OConnor delivered the opinion of the Court.
In Penry v. Lynaugh, 492 U. S. 302 (1989) (Penry I), we held that the Texas capital sentencing scheme provided a constitutionally inadequate vehicle for jurors to consider and give effect to the mitigating evidence of mental retardation and childhood abuse the petitioner had presented. The petitioner in this case argues that the same scheme was inadequate for jurors to give effect to his evidence of low intelligence. The Texas courts rejected his claim, and a Federal District Court denied his petition for a writ of habeas corpus. We conclude that reasonable jurists would find the district courts assessment of the constitutional claims debatable or wrong, Slack v. McDaniel , 529 U. S. 473, 484 (2000) , and therefore hold that a certificate of appealability should have issued.
I
Petitioner Robert Tennard was convicted by a jury of capital murder in October 1986. The evidence presented at trial indicated that Tennard and two accomplices killed two of his neighbors and robbed their house. Tennard himself stabbed one of the victims to death, and one of the accomplices killed the other victim with a hatchet.
During the penalty phase of the trial, defense counsel called only one witnessTennards parole officerwho testified that Tennards Department of Corrections record from a prior incarceration indicated that he had an IQ of 67. App. 2829. He testified that the IQ test would have been administered as a matter of course. Ibid. The report, which indicated that Tennard was 17 years old at the time it was prepared, was admitted into evidence. On cross-examination, the parole officer testified that he did not know who had administered the test. Id., at 30. The government introduced evidence in the penalty phase regarding a prior conviction for rape, committed when Tennard was 16. The rape victim testified that she had escaped through a window after Tennard permitted her to go to the bathroom to take a bath, promising him she wouldnt run away. Id., at 1617.
The jury was instructed to consider the appropriate punishment by answering the two special issues used at the time in Texas to establish whether a sentence of life imprisonment or death would be imposed:
Was the conduct of the defendant, Robert James Tennard, that caused the death of the deceased committed deliberately and with the reasonable expectation that the death of the deceased or another would result? Id., at 69 (the deliberateness special issue).
Is there a probability that the defendant, Robert James Tennard, would commit criminal acts of violence that would constitute a continuing threat to society? Id., at 70 (the future dangerousness special issue).
  And he believed her. This guy with the 67 IQ, and she goes in and, sure enough, she escapes, just like she should have. That is uncontroverted testimony before you, that we have got a man before us that has got an intelligence quotient . . . that is that low. Id., at 51.
In rebuttal, the prosecution suggested that the low IQ evidence was simply irrelevant to the question of mitigation:
But whether he has a low IQ or not is not really the issue. Because the legislature, in asking you to address that question [the future dangerousness special issue], the reasons why he became a danger are not really relevant. The fact that he is a danger, that the evidence shows hes a danger, is the criteria to use in answering that question. Id., at 60.
The jury answered both special issues in the affirmative, and Tennard was accordingly sentenced to death.
Unsuccessful on direct appeal, Tennard sought state postconviction relief. He argued that, in light of the instructions given to the jury, his death sentence had been obtained in violation of the Eighth Amendment as interpreted by this Court in Penry I . In that case, we had held that it is not enough simply to allow the defendant to present mitigating evidence to the sentencer. The sentencer must also be able to consider and give effect to that evidence in imposing sentence. Penry I , supra, at 319; see also Penry v. Johnson, 532 U. S. 782, 797 (2001) (Penry II) (describing give effect to language of Penry I as the key to that decision). We concluded that the same two special issues that were presented to Tennards jury (plus a third immaterial to the questions now before us) were insufficient for the jury in Penrys case to consider and give effect to Penrys evidence of mental retardation and childhood abuse, and therefore ran afoul of the Eighth Amendment. Penry I , 492 U. S., at 319328. His mental retardation evidence, we held, had relevance to [his] moral culpability beyond the scope of the [deliberateness] special verdict questio[n] because [p]ersonal culpability is not solely a function of a defendants capacity to act deliberately. Id. , at 322 (some brackets in original). Moreover, because the evidence concerning Penrys mental retardation indicated that one effect of his retardation is his inability to learn from his mistakes, his retardation was relevant to the future dangerousness special issue only as an aggravating factor. Id., at 323. As to the evidence of childhood abuse, we held that the two special issues simply failed to provide a vehicle for the jury to give [it] mitigating effect. Id., at 322324.
The Texas Court of Criminal Appeals rejected Tennards Penry claim. Ex parte Tennard , 960 S. W. 2d 57 (1997) (en banc). Writing for a plurality of four, Presiding Judge McCormick observed that the definition of mental retardation adopted in Texas involves three components ((1) subaverage general intellectual functioning; (2) concurrent deficits in adaptive behavior; and (3) onset during the early development period, id., at 60), and concluded: [Tennards] evidence of a low IQ score, standing alone, does not meet this definition. Qualitatively and quantitatively, [Tennards] low IQ evidence does not approach the level of Johnny Paul Penrys evidence of mental retardation… . [W]e find no evidence in this record that applicant is mentally retarded. Id., at 61.
The plurality went on to consider whether Tennard would be entitled to relief under Penry even if his low IQ fell within Penry s definition of mental retardation. 960 S. W. 2d, at 61. It held that he would not. The court explained that, unlike the evidence presented in Penrys case, there is no evidence … [that Tennards] low IQ rendered him unable to appreciate the wrongfulness of his conduct when he committed the offense, or that his low IQ rendered him unable to learn from his mistakes … or control his impulses … . Id., at 62. It found there was no danger that the jury would have given the evidence only aggravating effect in answering the future dangerousness special issue, and that the low IQ and gullibility evidence was not beyond the jurys effective reach because the jury could have used this evidence for a no answer to the deliberateness special issue. Ibid.
Two judges concurred separately, and wrote that this Court has sustained a Penry claim only when there is evidence of mental retardation. But even in those cases, the evidence of mental retardation was always something more than what was presented in this case. 960 S. W. 2d, at 64 (opinion of Meyers, J.) (citations omitted). Taking a more permissive view of evidence of impaired intellectual functioning than did the plurality ([F]or Penry purposes, courts should not distinguish between mental retardation and dementia, even though the onset of the latter may occur after age eighteen, id., at 65), the concurring judges nevertheless concluded that the record does not contain sufficient evidence to support Tennards Penry claim. 960 S. W. 2d , at 63. The concurring judges also rejected Tennards contention that evidence of an IQ of below 70 alone requires a Penry instruction because published opinions of the Texas courts had uniformly required more. Id., at 67.
Judge Baird dissented, maintaining that the Court of Criminal Appeals had consistent[ly] held, in the wake of Penry I , that evidence of mental retardation cannot be adequately considered within the statutory special issues. 960 S. W. 2d, at 67. The court had strayed from its precedent, Judge Baird wrote, and instead of asking simply whether the jury had a vehicle for considering the mitigating evidence, had weigh[ed] the sufficiency of [Tennards] mitigating evidence. Id., at 70. Judges Overstreet and Womack dissented without opinion. Id., at 63.
Tennard sought federal habeas corpus relief. The District Court denied his petition. Tennard v. Johnson, Civ. Action No. H984238 (S D Tex., July 25, 2000), App. 121. The court began by observing that [e]vidence of a single low score on an unidentified intelligence test is not evidence that Tennard was mentally retarded. Id., at 128. It then considered whether the 67 IQ score was within the effective reach of the jury. Ibid. Noting that Tennards low IQ score was not concealed from the jury; it was in evidence, and both sides argued its significance for punishment, the court concluded that the jury had adequate means, in the two special issues, by which to give effect to that mitigating evidence. Id., at 129. The court subsequently denied Tennard a certificate of appealability (COA). Civ. Action No. H984238 (S D Tex. Oct. 17, 2000), see App. 2.
The Court of Appeals for the Fifth Circuit, after full briefing and oral argument, issued an opinion holding that Tennard was not entitled to a COA because his Penry claim was not debatable among jurists of reason. Tennard v. Cockrell, 284 F. 3d 591 (2002). The court began by stating the test applied in the Fifth Circuit to Penry claims, which involves a threshold inquiry into whether the petitioner presented constitutionally relevant mitigating evidence, that is, evidence of a uniquely severe permanent handicap with which the defendant was burdened through no fault of his own, and evidence that the criminal act was attributable to this severe permanent condition. 284 F. 3d, at 595.
The court then held that Tennard was not entitled to a COA, for two reasons: First, it held that evidence of low IQ alone does not constitute a uniquely severe condition, and rejected Tennards claim that his evidence was of mental retardation, not just low IQ, because no evidence had been introduced tying his IQ score to retardation. Id., at 596. Second, it held that even if Tennards evidence was mental retardation evidence, his claim must fail because he did not show that the crime he committed was attributable to his low IQ. Id., at 596597. Judge Dennis dissented, concluding that the Texas courts application of Penry was unreasonable and that Tennard was entitled to habeas relief. 284 F. 3d, at 597604.
Tennard filed a petition for certiorari, and this Court granted the writ, vacated the judgment, and remanded for further consideration in light of Atkins v. Virginia, 536 U. S. 304 (2002) . Tennard v. Cockrell, 537 U. S. 802 (2002) . The Fifth Circuit took the remand to be for consideration of a substantive Atkins claim. It observed that Tennard has never argued that the Eighth Amendment prohibits his execution and reinstated its prior panel opinion. 317 F. 3d 476, 477 (2003). We again granted certiorari. 540 U. S. 945 (2003) .
II
A
A COA should issue if the applicant has made a substantial showing of the denial of a constitutional right, 28 U. S. C. §2253(c)(2), which we have interpreted to require that the petitioner must demonstrate that reasonable jurists would find the district courts assessment of the constitutional claims debatable or wrong. Slack v. McDaniel , 529 U. S., at 484; see also Miller-El v. Cockrell, 537 U. S. 322, 336 (2003) (Under the controlling standard, a petitioner must sho[w] that reasonable jurists could debate whether (or, for that matter, agree that) the petition should have been resolved in a different manner or that the issues presented were adequate to deserve encouragement to proceed further ). The petitioners arguments ultimately must be assessed under the deferential standard required by 28 U. S. C. §2254(d)(1): Relief may not be granted unless the state court adjudication resulted in a decision that was contrary to, or involved an unreasonable application of, clearly established Federal law, as determined by the Supreme Court of the United States.
The State has never disputed that Tennards Penry claim was properly preserved for federal habeas review. Not only did the state court consider the question on the merits, we note that the issue was also raised by defense counsel prior to trial in a motion to set aside the indictment on the ground, among others, that the Texas capital murder statutes do not explicitly allow the consideration of any specific mitigating circumstances at the punishment phase of the prosecution and, consequently, are violative of the accuseds right to be free from cruel and unusual punishment and are also void for vagueness. Defendants Motion to Set Aside the Indictment, in Cause No. 431127 (248th Jud. Dist. Ct. Harris County, Tex., May 28, 1986), p. 4.
B
Despite paying lipservice to the principles guiding issuance of a COA, Tennard v. Cockrell, supra, at 594, the Fifth Circuits analysis proceeded along a distinctly different track. Rather than examining the District Courts analysis of the Texas court decision, it invoked its own restrictive gloss on Penry I:
In reviewing a Penry claim, we must determine whether the mitigating evidence introduced at trial was constitutionally relevant and beyond the effective reach of the jury. … To be constitutionally relevant, the evidence must show (1) a uniquely severe permanent handicap with which the defendant was burdened through no fault of his own, … and (2) that the criminal act was attributable to this severe permanent condition. 284 F. 3d, at 595 (quoting Davis v. Scott, 51 F. 3d, 457, 460461 (CA5 1998)).
This test for constitutional relevance, characterized by the State at oral argument as a threshold screening test, Tr. of Oral Arg.10, 28, appears to be applied uniformly in the Fifth Circuit to Penry claims. See, e.g., Bigby v. Cockrell , 340 F. 3d 259, 273 (2003); Robertson v. Cockrell , 325 F. 3d 243, 251 (2003) (en banc); Smith v. Cockrell , 311 F. 3d 661, 680 (2002); Blue v. Cockrell , 298 F. 3d 318, 320321 (2002); Davis v. Scott , 51 F. 3d 457, 460461 (1995). Only after the court finds that certain mitigating evidence is constitutionally relevant will it consider whether that evidence was within the effective reach of the jur[y]. E.g., Smith, supra, at 680 (court asks whether evidence was constitutionally relevant and, if so, will consider whether it was within jurys effective reach). In the decision below, the Fifth Circuit concluded that Tennard was precluded from establishing a Penry claim because his low IQ evidence bore no nexus to the crime, and so did not move on to the effective reach question. 284 F. 3d, at 597.
The Fifth Circuits test has no foundation in the decisions of this Court. Neither Penry I nor its progeny screened mitigating evidence for constitutional relevance before considering whether the jury instructions comported with the Eighth Amendment. Indeed, the mitigating evidence presented in Penry I was concededly relevant, see Tr. of Oral Arg., O. T. 1988, No. 876177, pp. 3436, so even if limiting principles regarding relevance were suggested in our opinionand we do not think they werethey could not have been material to the holding.
When we addressed directly the relevance standard applicable to mitigating evidence in capital cases in McKoy v. North Carolina, 494 U. S. 433, 440441 (1990) , we spoke in the most expansive terms. We established that the meaning of relevance is no different in the context of mitigating evidence introduced in a capital sentencing proceeding than in any other context, and thus the general evidentiary standard any tendency to make the existence of any fact that is of consequence to the determination of the action more probable or less probable than it would be without the evidence applies. Id., at 440 (quoting New Jersey v. T. L. O., 469 U. S. 325, 345 (1985) ). We quoted approvingly from a dissenting opinion in the state court: Relevant mitigating evidence is evidence which tends logically to prove or disprove some fact or circumstance which a fact-finder could reasonably deem to have mitigating value. 494 U. S., at 440 (quoting State v. McKoy , 323 N. C. 1, 5556, 372 S. E. 2d, 12, 45 (1988) (opinion of Exum, C. J.)). Thus, a State cannot bar the consideration of … evidence if the sentencer could reasonably find that it warrants a sentence less than death. 494 U. S., at 441.
Once this low threshold for relevance is met, the Eighth Amendment requires that the jury be able to consider and give effect to a capital defendants mitigating evidence. Boyde v. California, 494 U. S. 370, 377378 (1990) (citing Lockett v. Ohio, 438 U. S. 586 (1978) ; Eddings v. Oklahoma, 455 U. S. 104 (1982) ; Penry I, 492 U. S. 302 (1989) ); see also Payne v. Tennessee, 501 U. S. 808, 822 (1991) (We have held that a State cannot preclude the sentencer from considering any relevant mitigating evidence that the defendant proffers in support of a sentence less than death… . [V]irtually no limits are placed on the relevant mitigating evidence a capital defendant may introduce concerning his own circumstances (quoting Eddings , supra , at 114)).
The Fifth Circuits test is inconsistent with these principles. Most obviously, the test will screen out any positive aspect of a defendants character, because good character traits are neither handicap[s] nor typically traits to which criminal activity is attributable. In Skipper v. South Carolina, 476 U. S. 1, 5 (1986) , however, we made clear that good-character evidence can be evidence that, [u]nder Eddings , … may not be excluded from the sentencers consideration. We observed that even though the petitioners evidence of good conduct in jail did not relate specifically to petitioners culpability for the crime he committed, there is no question but that such [evidence] … would be mitigating in the sense that [it] might serve as a basis for a sentence less than death. Lockett , supra , at 604 id., at 45 (citation omitted). Such evidence, we said, of a defendants disposition to make a well-behaved and peaceful adjustment to life in prison is … by its nature relevant to the sentencing determination. Id., at 7. Of course, the Texas courts might reasonably conclude that evidence of good conduct in jail was within the jurys effective reach via the future dangerousness special issue. See Franklin v. Lynaugh, 487 U. S. 164, 177178 (1988) (plurality opinion); id., at 185186 ( OConnor, J. , concurring in judgment). But under the Fifth Circuits test, the evidence would have been screened out before the time came to consider that question.
In Tennards case, the Fifth Circuit invoked both the uniquely severe and the nexus elements of its test to deny him relief under Penry I . Tennard v. Cockrell, 284 F. 3d, at 596 (contrasting Tennards low IQ evidence, which did not constitute a uniquely severe condition, with mental retardation, a severe permanent condition); id., at 596597 (concluding that Penry claims must fail because [Tennard] made no showing at trial that the criminal act was attributable to his condition).* * Neither ground provided an adequate reason to fail to reach the heart of Tennards Penry claims.
We have never denied that gravity has a place in the relevance analysis, insofar as evidence of a trivial feature of the defendants character or the circumstances of the crime is unlikely to have any tendency to mitigate the defendants culpability. See Skipper , supra, at 7, n. 2 (We do not hold that all facets of the defendants ability to adjust to prison life must be treated as relevant and potentially mitigating. For example, we have no quarrel with the statement … that how often [the defendant] will take a shower is irrelevant to the sentencing determination (quoting State v. Plath , 281 S. C. 1, 15, 313 S. E. 2d 619, 627 (1984)). However, to say that only those features and circumstances that a panel of federal appellate judges deems to be severe (let alone uniquely severe) could have such a tendency is incorrect. Rather, the question is simply whether the evidence is of such a character that it might serve as a basis for a sentence less than death, Skipper , supra, at 5.
The Fifth Circuit was likewise wrong to have refused to consider the debatability of the Penry question on the ground that Tennard had not adduced evidence that his crime was attributable to his low IQ. In Atkins v.   Equally, we cannot countenance the suggestion that low IQ evidence is not relevant mitigating evidenceand thus that the Penry question need not even be askedunless the defendant also establishes a nexus to the crime.
The State claims that the Fifth Circuits Penry I jurisprudence is not at issue in this case. Brief for Respondent 35, n. 21; Tr. of Oral Arg. 33. To the contrary, that jurisprudence is directly at issue because the Fifth Circuit denied Tennard relief on the ground that he did not satisfy the requirements imposed by its constitutional relevance test. As we have explained, the Fifth Circuits screening test has no basis in our precedents and, indeed, is inconsistent with the standard we have adopted for relevance in the capital sentencing context. We therefore hold that the Fifth Circuit assessed Tennards Penry claim under an improper legal standard. Cf. Miller-El v. Cockrell, 537 U. S., at 341 (holding, on certiorari review of the denial of a COA, that the Fifth Circuit had applied an incorrect standard by improperly merging the requirements of two statutory sections).
C
We turn to the analysis the Fifth Circuit should have conducted: Has Tennard demonstrate[d] that reasonable jurists would find the district courts assessment of the constitutional claims debatable or wrong? Slack v. McDaniel , 529 U. S., at 484. We conclude that he has.
Reasonable jurists could conclude that the low IQ evidence Tennard presented was relevant mitigating evidence. Evidence of significantly impaired intellectual functioning is obviously evidence that might serve as a basis for a sentence less than death, Skipper , 476 U. S., at 5; see also, e.g., Wiggins v. Smith, 539 U. S. 510, 535 (2003) (observing, with respect to individual with IQ of 79, that Wiggins[] … diminished mental capacitie[s] further augment his mitigation case); Burger v. Kemp, 483 U. S. 776 n. 7 (1987) (noting that petitioner had an IQ of 82 and functioned at the level of a 12-year-old child, and later that [i]n light of petitioners youth at the time of the offense, … testimony that his mental and emotional development were at a level several years below his chronological age could not have been excluded by the state court (quoting Eddings , 455 U. S., at 116)).
Reasonable jurists also could conclude that the Texas Court of Criminal Appeals application of Penry to the facts of Tennards case was unreasonable. The relationship between the special issues and Tennards low IQ evidence has the same essential features as the relationship between the special issues and Penrys mental retardation evidence. Impaired intellectual functioning has mitigating dimension beyond the impact it has on the individuals ability to act deliberately. See Penry I , 492 U. S., at 322. A reasonable jurist could conclude that the jury might well have given Tennards low IQ evidence aggravating effect in considering his future dangerousness, not only as a matter of probable inference from the evidence but also because the prosecutor told them to do so: [W]hether he has a low IQ or not is not really the issue. Because the legislature, in asking you to address that question, the reasons why he became a danger are not really relevant. The fact that he is a danger, that the evidence shows hes a danger, is the criteria to use in answering that question. App 60. Indeed, the prosecutors comments pressed exactly the most problematic interpretation of the special issues, suggesting that Tennards low IQ was irrelevant in mitigation, but relevant to the question whether he posed a future danger.
* * *
We hold that the Fifth Circuits uniquely severe permanent handicap and nexus tests are incorrect, and we reject them. We hold that reasonable jurists would find debatable or wrong the District Courts disposition of Tennards low-IQ-based Penry claim, and that Tennard is therefore entitled to a certificate of appealability. The judgment of the United States Court of Appeals for the Fifth Circuit is reversed, and the case is remanded for further proceedings consistent with this opinion.
It is so ordered.
* * The Fifth Circuit stated that a majority of the Court of Criminal Appeals found no evidence in this record that [Tennard] is mentally retarded. 284 F. 3d, at 596597. As described above, however, that was the conclusion of a four-judge plurality; the narrowest and thus controlling opinion on this point, correctly described by the Fifth Circuit as conclud[ing] that there was not enough evidence of mental retardation in the record to support Tennards claim, id., at 596, n. 5 (emphasis added), is Judge Meyers concurring opinion.
Opinion
ROBERT JAMES TENNARD, PETITIONER
v.
DOUG
DRETKE, DIRECTOR, TEXAS DEPARTMENT OF
CRIMINAL JUSTICE, CORRECTIONAL
INSTITUTIONS DIVISION
Justice OConnor delivered the opinion of the Court.
In Penry v. Lynaugh, 492 U. S. 302 (1989) (Penry I), we held that the Texas capital sentencing scheme provided a constitutionally inadequate vehicle for jurors to consider and give effect to the mitigating evidence of mental retardation and childhood abuse the petitioner had presented. The petitioner in this case argues that the same scheme was inadequate for jurors to give effect to his evidence of low intelligence. The Texas courts rejected his claim, and a Federal District Court denied his petition for a writ of habeas corpus. We conclude that reasonable jurists would find the district courts assessment of the constitutional claims debatable or wrong, Slack v. McDaniel , 529 U. S. 473, 484 (2000) , and therefore hold that a certificate of appealability should have issued.
I
Petitioner Robert Tennard was convicted by a jury of capital murder in October 1986. The evidence presented at trial indicated that Tennard and two accomplices killed two of his neighbors and robbed their house. Tennard himself stabbed one of the victims to death, and one of the accomplices killed the other victim with a hatchet.
During the penalty phase of the trial, defense counsel called only one witnessTennards parole officerwho testified that Tennards Department of Corrections record from a prior incarceration indicated that he had an IQ of 67. App. 2829. He testified that the IQ test would have been administered as a matter of course. Ibid. The report, which indicated that Tennard was 17 years old at the time it was prepared, was admitted into evidence. On cross-examination, the parole officer testified that he did not know who had administered the test. Id., at 30. The government introduced evidence in the penalty phase regarding a prior conviction for rape, committed when Tennard was 16. The rape victim testified that she had escaped through a window after Tennard permitted her to go to the bathroom to take a bath, promising him she wouldnt run away. Id., at 1617.
The jury was instructed to consider the appropriate punishment by answering the two special issues used at the time in Texas to establish whether a sentence of life imprisonment or death would be imposed:
Was the conduct of the defendant, Robert James Tennard, that caused the death of the deceased committed deliberately and with the reasonable expectation that the death of the deceased or another would result? Id., at 69 (the deliberateness special issue).
Is there a probability that the defendant, Robert James Tennard, would commit criminal acts of violence that would constitute a continuing threat to society? Id., at 70 (the future dangerousness special issue).
  And he believed her. This guy with the 67 IQ, and she goes in and, sure enough, she escapes, just like she should have. That is uncontroverted testimony before you, that we have got a man before us that has got an intelligence quotient . . . that is that low. Id., at 51.
In rebuttal, the prosecution suggested that the low IQ evidence was simply irrelevant to the question of mitigation:
But whether he has a low IQ or not is not really the issue. Because the legislature, in asking you to address that question [the future dangerousness special issue], the reasons why he became a danger are not really relevant. The fact that he is a danger, that the evidence shows hes a danger, is the criteria to use in answering that question. Id., at 60.
The jury answered both special issues in the affirmative, and Tennard was accordingly sentenced to death.
Unsuccessful on direct appeal, Tennard sought state postconviction relief. He argued that, in light of the instructions given to the jury, his death sentence had been obtained in violation of the Eighth Amendment as interpreted by this Court in Penry I . In that case, we had held that it is not enough simply to allow the defendant to present mitigating evidence to the sentencer. The sentencer must also be able to consider and give effect to that evidence in imposing sentence. Penry I , supra, at 319; see also Penry v. Johnson, 532 U. S. 782, 797 (2001) (Penry II) (describing give effect to language of Penry I as the key to that decision). We concluded that the same two special issues that were presented to Tennards jury (plus a third immaterial to the questions now before us) were insufficient for the jury in Penrys case to consider and give effect to Penrys evidence of mental retardation and childhood abuse, and therefore ran afoul of the Eighth Amendment. Penry I , 492 U. S., at 319328. His mental retardation evidence, we held, had relevance to [his] moral culpability beyond the scope of the [deliberateness] special verdict questio[n] because [p]ersonal culpability is not solely a function of a defendants capacity to act deliberately. Id. , at 322 (some brackets in original). Moreover, because the evidence concerning Penrys mental retardation indicated that one effect of his retardation is his inability to learn from his mistakes, his retardation was relevant to the future dangerousness special issue only as an aggravating factor. Id., at 323. As to the evidence of childhood abuse, we held that the two special issues simply failed to provide a vehicle for the jury to give [it] mitigating effect. Id., at 322324.
The Texas Court of Criminal Appeals rejected Tennards Penry claim. Ex parte Tennard , 960 S. W. 2d 57 (1997) (en banc). Writing for a plurality of four, Presiding Judge McCormick observed that the definition of mental retardation adopted in Texas involves three components ((1) subaverage general intellectual functioning; (2) concurrent deficits in adaptive behavior; and (3) onset during the early development period, id., at 60), and concluded: [Tennards] evidence of a low IQ score, standing alone, does not meet this definition. Qualitatively and quantitatively, [Tennards] low IQ evidence does not approach the level of Johnny Paul Penrys evidence of mental retardation… . [W]e find no evidence in this record that applicant is mentally retarded. Id., at 61.
The plurality went on to consider whether Tennard would be entitled to relief under Penry even if his low IQ fell within Penry s definition of mental retardation. 960 S. W. 2d, at 61. It held that he would not. The court explained that, unlike the evidence presented in Penrys case, there is no evidence … [that Tennards] low IQ rendered him unable to appreciate the wrongfulness of his conduct when he committed the offense, or that his low IQ rendered him unable to learn from his mistakes … or control his impulses … . Id., at 62. It found there was no danger that the jury would have given the evidence only aggravating effect in answering the future dangerousness special issue, and that the low IQ and gullibility evidence was not beyond the jurys effective reach because the jury could have used this evidence for a no answer to the deliberateness special issue. Ibid.
Two judges concurred separately, and wrote that this Court has sustained a Penry claim only when there is evidence of mental retardation. But even in those cases, the evidence of mental retardation was always something more than what was presented in this case. 960 S. W. 2d, at 64 (opinion of Meyers, J.) (citations omitted). Taking a more permissive view of evidence of impaired intellectual functioning than did the plurality ([F]or Penry purposes, courts should not distinguish between mental retardation and dementia, even though the onset of the latter may occur after age eighteen, id., at 65), the concurring judges nevertheless concluded that the record does not contain sufficient evidence to support Tennards Penry claim. 960 S. W. 2d , at 63. The concurring judges also rejected Tennards contention that evidence of an IQ of below 70 alone requires a Penry instruction because published opinions of the Texas courts had uniformly required more. Id., at 67.
Judge Baird dissented, maintaining that the Court of Criminal Appeals had consistent[ly] held, in the wake of Penry I , that evidence of mental retardation cannot be adequately considered within the statutory special issues. 960 S. W. 2d, at 67. The court had strayed from its precedent, Judge Baird wrote, and instead of asking simply whether the jury had a vehicle for considering the mitigating evidence, had weigh[ed] the sufficiency of [Tennards] mitigating evidence. Id., at 70. Judges Overstreet and Womack dissented without opinion. Id., at 63.
Tennard sought federal habeas corpus relief. The District Court denied his petition. Tennard v. Johnson, Civ. Action No. H984238 (S D Tex., July 25, 2000), App. 121. The court began by observing that [e]vidence of a single low score on an unidentified intelligence test is not evidence that Tennard was mentally retarded. Id., at 128. It then considered whether the 67 IQ score was within the effective reach of the jury. Ibid. Noting that Tennards low IQ score was not concealed from the jury; it was in evidence, and both sides argued its significance for punishment, the court concluded that the jury had adequate means, in the two special issues, by which to give effect to that mitigating evidence. Id., at 129. The court subsequently denied Tennard a certificate of appealability (COA). Civ. Action No. H984238 (S D Tex. Oct. 17, 2000), see App. 2.
The Court of Appeals for the Fifth Circuit, after full briefing and oral argument, issued an opinion holding that Tennard was not entitled to a COA because his Penry claim was not debatable among jurists of reason. Tennard v. Cockrell, 284 F. 3d 591 (2002). The court began by stating the test applied in the Fifth Circuit to Penry claims, which involves a threshold inquiry into whether the petitioner presented constitutionally relevant mitigating evidence, that is, evidence of a uniquely severe permanent handicap with which the defendant was burdened through no fault of his own, and evidence that the criminal act was attributable to this severe permanent condition. 284 F. 3d, at 595.
The court then held that Tennard was not entitled to a COA, for two reasons: First, it held that evidence of low IQ alone does not constitute a uniquely severe condition, and rejected Tennards claim that his evidence was of mental retardation, not just low IQ, because no evidence had been introduced tying his IQ score to retardation. Id., at 596. Second, it held that even if Tennards evidence was mental retardation evidence, his claim must fail because he did not show that the crime he committed was attributable to his low IQ. Id., at 596597. Judge Dennis dissented, concluding that the Texas courts application of Penry was unreasonable and that Tennard was entitled to habeas relief. 284 F. 3d, at 597604.
Tennard filed a petition for certiorari, and this Court granted the writ, vacated the judgment, and remanded for further consideration in light of Atkins v. Virginia, 536 U. S. 304 (2002) . Tennard v. Cockrell, 537 U. S. 802 (2002) . The Fifth Circuit took the remand to be for consideration of a substantive Atkins claim. It observed that Tennard has never argued that the Eighth Amendment prohibits his execution and reinstated its prior panel opinion. 317 F. 3d 476, 477 (2003). We again granted certiorari. 540 U. S. 945 (2003) .
II
A
A COA should issue if the applicant has made a substantial showing of the denial of a constitutional right, 28 U. S. C. §2253(c)(2), which we have interpreted to require that the petitioner must demonstrate that reasonable jurists would find the district courts assessment of the constitutional claims debatable or wrong. Slack v. McDaniel , 529 U. S., at 484; see also Miller-El v. Cockrell, 537 U. S. 322, 336 (2003) (Under the controlling standard, a petitioner must sho[w] that reasonable jurists could debate whether (or, for that matter, agree that) the petition should have been resolved in a different manner or that the issues presented were adequate to deserve encouragement to proceed further ). The petitioners arguments ultimately must be assessed under the deferential standard required by 28 U. S. C. §2254(d)(1): Relief may not be granted unless the state court adjudication resulted in a decision that was contrary to, or involved an unreasonable application of, clearly established Federal law, as determined by the Supreme Court of the United States.
The State has never disputed that Tennards Penry claim was properly preserved for federal habeas review. Not only did the state court consider the question on the merits, we note that the issue was also raised by defense counsel prior to trial in a motion to set aside the indictment on the ground, among others, that the Texas capital murder statutes do not explicitly allow the consideration of any specific mitigating circumstances at the punishment phase of the prosecution and, consequently, are violative of the accuseds right to be free from cruel and unusual punishment and are also void for vagueness. Defendants Motion to Set Aside the Indictment, in Cause No. 431127 (248th Jud. Dist. Ct. Harris County, Tex., May 28, 1986), p. 4.
B
Despite paying lipservice to the principles guiding issuance of a COA, Tennard v. Cockrell, supra, at 594, the Fifth Circuits analysis proceeded along a distinctly different track. Rather than examining the District Courts analysis of the Texas court decision, it invoked its own restrictive gloss on Penry I:
In reviewing a Penry claim, we must determine whether the mitigating evidence introduced at trial was constitutionally relevant and beyond the effective reach of the jury. … To be constitutionally relevant, the evidence must show (1) a uniquely severe permanent handicap with which the defendant was burdened through no fault of his own, … and (2) that the criminal act was attributable to this severe permanent condition. 284 F. 3d, at 595 (quoting Davis v. Scott, 51 F. 3d, 457, 460461 (CA5 1998)).
This test for constitutional relevance, characterized by the State at oral argument as a threshold screening test, Tr. of Oral Arg.10, 28, appears to be applied uniformly in the Fifth Circuit to Penry claims. See, e.g., Bigby v. Cockrell , 340 F. 3d 259, 273 (2003); Robertson v. Cockrell , 325 F. 3d 243, 251 (2003) (en banc); Smith v. Cockrell , 311 F. 3d 661, 680 (2002); Blue v. Cockrell , 298 F. 3d 318, 320321 (2002); Davis v. Scott , 51 F. 3d 457, 460461 (1995). Only after the court finds that certain mitigating evidence is constitutionally relevant will it consider whether that evidence was within the effective reach of the jur[y]. E.g., Smith, supra, at 680 (court asks whether evidence was constitutionally relevant and, if so, will consider whether it was within jurys effective reach). In the decision below, the Fifth Circuit concluded that Tennard was precluded from establishing a Penry claim because his low IQ evidence bore no nexus to the crime, and so did not move on to the effective reach question. 284 F. 3d, at 597.
The Fifth Circuits test has no foundation in the decisions of this Court. Neither Penry I nor its progeny screened mitigating evidence for constitutional relevance before considering whether the jury instructions comported with the Eighth Amendment. Indeed, the mitigating evidence presented in Penry I was concededly relevant, see Tr. of Oral Arg., O. T. 1988, No. 876177, pp. 3436, so even if limiting principles regarding relevance were suggested in our opinionand we do not think they werethey could not have been material to the holding.
When we addressed directly the relevance standard applicable to mitigating evidence in capital cases in McKoy v. North Carolina, 494 U. S. 433, 440441 (1990) , we spoke in the most expansive terms. We established that the meaning of relevance is no different in the context of mitigating evidence introduced in a capital sentencing proceeding than in any other context, and thus the general evidentiary standard any tendency to make the existence of any fact that is of consequence to the determination of the action more probable or less probable than it would be without the evidence applies. Id., at 440 (quoting New Jersey v. T. L. O., 469 U. S. 325, 345 (1985) ). We quoted approvingly from a dissenting opinion in the state court: Relevant mitigating evidence is evidence which tends logically to prove or disprove some fact or circumstance which a fact-finder could reasonably deem to have mitigating value. 494 U. S., at 440 (quoting State v. McKoy , 323 N. C. 1, 5556, 372 S. E. 2d, 12, 45 (1988) (opinion of Exum, C. J.)). Thus, a State cannot bar the consideration of … evidence if the sentencer could reasonably find that it warrants a sentence less than death. 494 U. S., at 441.
Once this low threshold for relevance is met, the Eighth Amendment requires that the jury be able to consider and give effect to a capital defendants mitigating evidence. Boyde v. California, 494 U. S. 370, 377378 (1990) (citing Lockett v. Ohio, 438 U. S. 586 (1978) ; Eddings v. Oklahoma, 455 U. S. 104 (1982) ; Penry I, 492 U. S. 302 (1989) ); see also Payne v. Tennessee, 501 U. S. 808, 822 (1991) (We have held that a State cannot preclude the sentencer from considering any relevant mitigating evidence that the defendant proffers in support of a sentence less than death… . [V]irtually no limits are placed on the relevant mitigating evidence a capital defendant may introduce concerning his own circumstances (quoting Eddings , supra , at 114)).
The Fifth Circuits test is inconsistent with these principles. Most obviously, the test will screen out any positive aspect of a defendants character, because good character traits are neither handicap[s] nor typically traits to which criminal activity is attributable. In Skipper v. South Carolina, 476 U. S. 1, 5 (1986) , however, we made clear that good-character evidence can be evidence that, [u]nder Eddings , … may not be excluded from the sentencers consideration. We observed that even though the petitioners evidence of good conduct in jail did not relate specifically to petitioners culpability for the crime he committed, there is no question but that such [evidence] … would be mitigating in the sense that [it] might serve as a basis for a sentence less than death. Lockett , supra , at 604 id., at 45 (citation omitted). Such evidence, we said, of a defendants disposition to make a well-behaved and peaceful adjustment to life in prison is … by its nature relevant to the sentencing determination. Id., at 7. Of course, the Texas courts might reasonably conclude that evidence of good conduct in jail was within the jurys effective reach via the future dangerousness special issue. See Franklin v. Lynaugh, 487 U. S. 164, 177178 (1988) (plurality opinion); id., at 185186 ( OConnor, J. , concurring in judgment). But under the Fifth Circuits test, the evidence would have been screened out before the time came to consider that question.
In Tennards case, the Fifth Circuit invoked both the uniquely severe and the nexus elements of its test to deny him relief under Penry I . Tennard v. Cockrell, 284 F. 3d, at 596 (contrasting Tennards low IQ evidence, which did not constitute a uniquely severe condition, with mental retardation, a severe permanent condition); id., at 596597 (concluding that Penry claims must fail because [Tennard] made no showing at trial that the criminal act was attributable to his condition).* * Neither ground provided an adequate reason to fail to reach the heart of Tennards Penry claims.
We have never denied that gravity has a place in the relevance analysis, insofar as evidence of a trivial feature of the defendants character or the circumstances of the crime is unlikely to have any tendency to mitigate the defendants culpability. See Skipper , supra, at 7, n. 2 (We do not hold that all facets of the defendants ability to adjust to prison life must be treated as relevant and potentially mitigating. For example, we have no quarrel with the statement … that how often [the defendant] will take a shower is irrelevant to the sentencing determination (quoting State v. Plath , 281 S. C. 1, 15, 313 S. E. 2d 619, 627 (1984)). However, to say that only those features and circumstances that a panel of federal appellate judges deems to be severe (let alone uniquely severe) could have such a tendency is incorrect. Rather, the question is simply whether the evidence is of such a character that it might serve as a basis for a sentence less than death, Skipper , supra, at 5.
The Fifth Circuit was likewise wrong to have refused to consider the debatability of the Penry question on the ground that Tennard had not adduced evidence that his crime was attributable to his low IQ. In Atkins v.   Equally, we cannot countenance the suggestion that low IQ evidence is not relevant mitigating evidenceand thus that the Penry question need not even be askedunless the defendant also establishes a nexus to the crime.