TENNARD v. DRETKE, DIRECTOR, TEXAS DEPART- MENT OF CRIMINAL JUSTICE, CORRECTIONAL INSTITUTIONS DIVISION

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Syllabus
TENNARD v. DRETKE, DIRECTOR, TEXAS DEPART-
MENT OF CRIMINAL JUSTICE, CORRECTIONAL
INSTITUTIONS DIVISION
certiorari to the united states court of appeals for
the fifth circuit
No. 02–10038. Argued March 22, 2004—Decided June 24, 2004
During his capital murder trial’s penalty phase, petitioner Tennard pre-
sented evidence that he had an IQ of 67. The jury was instructed to
determine the appropriate punishment by considering two “special is-
sues,” which inquired into whether the crime was committed deliber-
ately 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 Penry’s
mitigating mental retardation and childhood abuse evidence. Tennard’s
jury answered both special issues affirmatively, and Tennard was sen-
tenced to death. The Federal District Court denied Tennard’s 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 Tennard’s mitigating
evidence, asking whether it met the Fifth Circuit’s standard of “consti-
tutional relevance” in Penry cases—that 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 Tennard’s
IQ to retardation, and (2) even if his low IQ amounted to mental retarda-
tion 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 court’s assess-
ment of the constitutional claims debatable or wrong,” Slack v. McDan-
iel, 529 U. S. 473, 484, a COA should have issued. Pp. 282–289.
(a) A COA should issue if an applicant has “made a substantial show-
ing of the denial of a constitutional right,” 28 U. S. C. § 2253(c)(2), by
demonstrating “that reasonable jurists would find the district court’s
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

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Syllabus
established Federal law, as determined by” this Court. § 2254(d)(1).
Pp. 282–283.
(b) The Fifth Circuit assessed Tennard’s Penry claim under an im-
proper standard. Its threshold “constitutional relevance” screening
test has no foundation in this Court’s 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, 440–441, finding applicable the general eviden-
tiary 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 re-
quires that the jury be able to consider and give effect to” a capital
defendant’s mitigating evidence. Boyde v. California, 494 U. S. 370,
377–378. The Fifth Circuit’s test is inconsistent with these principles.
Thus, neither the “uniquely severe” nor the “nexus” element of the Fifth
Circuit’s test was a proper reason not to reach the substance of Ten-
nard’s Penry claims. Pp. 283–288.
(c) Turning to the analysis that the Fifth Circuit should have con-
ducted, reasonable jurists could conclude that Tennard’s 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 Tennard’s low IQ evidence has the same
essential features as that between those issues and Penry’s mental re-
tardation evidence. Impaired intellectual functioning has mitigating di-
mension 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 Tennard’s future danger-
ousness. Indeed, the prosecutor pressed exactly the most problematic
interpretation of the special issues, suggesting that Tennard’s low IQ
was irrelevant in mitigation, but relevant to future dangerousness.
Pp. 288–289.
317 F. 3d 476, reversed and remanded.
O’Connor, J., delivered the opinion of the Court, in which Stevens,
Kennedy, Souter, Ginsburg, and Breyer, JJ., joined. Rehnquist,
C. J., post, p. 289, Scalia, J., post, p. 293, and Thomas, J., post, p. 294, filed
dissenting opinions.
Robert C. Owen argued the cause for petitioner. With
him on the briefs were Jordan M. Steiker and Richard H.
Burr.

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Edward L. Marshall, Assistant Attorney General of
Texas, argued the cause for respondent. With him on the
brief were Greg Abbott, Attorney General, Barry R. McBee,
First Assistant Attorney General, Don Clemmer, Acting
Deputy Attorney General, and Gena Bunn and Tommy L.
Skaggs, Assistant Attorneys General.*
Justice O’Connor 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 peti-
tioner in this case argues that the same scheme was inade-
quate for jurors to give effect to his evidence of low intelli-
gence. 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
court’s 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 capi-
tal 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.
*Briefs of amici curiae urging reversal were filed for the American
Association on Mental Retardation et al. by James W. Ellis, Michael B.
Browde, Christian G. Fritz, April Land, and Robert L. Schwartz; for the
National Mental Health Association by J. Brett Busby, Claudia Wilson
Frost, and Charles S. Kelley; and for the Texas Defender Service et al. by
Peter Buscemi, Anthony C. Roth, and Jeffrey J. Pokorak.

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During the penalty phase of the trial, defense counsel
called only one witness—Tennard’s parole officer—who testi-
fied that Tennard’s Department of Corrections record from a
prior incarceration indicated that he had an IQ of 67. App.
28–29. He testified that the IQ test would have been admin-
istered as a matter of course. Ibid. The report, which indi-
cated that Tennard was 17 years old at the time it was pre-
pared, 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 intro-
duced evidence in the penalty phase regarding a prior con-
viction 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 would not run away. Id., at 16–17.
The jury was instructed to consider the appropriate pun-
ishment by answering the two “special issues” used at the
time in Texas to establish whether a sentence of life impris-
onment or death would be imposed:
“Was the conduct of the defendant, Robert James Ten-
nard, 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”).
In his penalty phase closing argument, defense counsel re-
lied on both the IQ score and the rape victim’s testimony to
suggest that Tennard’s limited mental faculties and gullible
nature mitigated his culpability:
“Tennard has got a 67 IQ. The same guy that told this
poor unfortunate woman [the rape victim] that was try-
ing to work that day, ‘Well, if I let you in there, will you

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leave?’ 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 be-
fore 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 rele-
vant. The fact that he is a danger, that the evidence
shows he’s 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 post-
conviction 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 sen-
tence.” 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 pre-
sented to Tennard’s jury (plus a third immaterial to the ques-
tions now before us) were insufficient for the jury in Penry’s
case to consider and give effect to Penry’s evidence of mental
retardation and childhood abuse, and therefore ran afoul of
the Eighth Amendment. Penry I, 492 U. S., at 319–328.
His mental retardation evidence, we held, “ ‘had relevance to
[his] moral culpability beyond the scope of the [deliberate-

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ness] special verdict questio[n]’ ” because “[p]ersonal culpa-
bility is not solely a function of a defendant’s capacity to
act ‘deliberately.’ ” Id., at 322 (some brackets in original).
Moreover, because the “evidence concerning Penry’s mental
retardation indicated that one effect of his retardation is his
inability to learn from his mistakes,” his retardation was rel-
evant 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 322–324.
The Texas Court of Criminal Appeals rejected Tennard’s
Penry claim. Ex parte Tennard, 960 S. W. 2d 57 (1997) (en
banc). Writing for a plurality of four, Presiding Judge Mc-
Cormick 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 develop-
ment period,” id., at 60), and concluded: “[Tennard’s] evi-
dence of a low IQ score, standing alone, does not meet this
definition. Qualitatively and quantitatively [Tennard’s] low
IQ evidence does not approach the level of Johnny Paul Pen-
ry’s 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 Penry’s case, “there is
no evidence [that Tennard’s] low IQ rendered him unable to
appreciate the wrongfulness of his conduct when he com-
mitted 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

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answering” the future dangerousness special issue, and that
the low IQ and gullibility evidence was not beyond the jury’s
effective reach because the jury “could have used this evi-
dence 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 evi-
dence 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 func-
tioning than did the plurality (“[F]or Penry purposes, courts
should not distinguish between mental retardation and de-
mentia,” 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 evi-
dence to support” Tennard’s Penry claim. 960 S. W. 2d,
at 63. The concurring judges also rejected Tennard’s con-
tention 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 ade-
quately 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 [Tennard’s] mitigating evi-
dence.” Id., at 70. Judges Overstreet and Womack dis-
sented without opinion. Id., at 63.
Tennard sought federal habeas corpus relief. The District
Court denied his petition. Tennard v. Johnson, Civ. Action
No. H–98–4238 (SD Tex., July 25, 2000), App. 121. The
court began by observing that “[e]vidence of a single low

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score on an unidentified intelligence test is not evidence that
Tennard was mentally retarded.” Id., at 128. It then con-
sidered whether the 67 IQ score was “within ‘the effective
reach’ of the jury.” Ibid. Noting that “Tennard’s 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 mitigat-
ing evidence. Id., at 129. The court subsequently denied
Tennard a certificate of appealability (COA). Civ. Action
No. H–98–4238 (SD 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 pre-
sented “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 Tennard’s claim that his evidence was of mental re-
tardation, not just low IQ, because no evidence had been in-
troduced tying his IQ score to retardation. Id., at 596.
Second, it held that even if Tennard’s 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 596–597. Judge Dennis dissented, conclud-
ing that the Texas court’s application of Penry was unreason-
able and that Tennard was entitled to habeas relief. 284
F. 3d, at 597–604.

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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 exe-
cution” and reinstated its prior panel opinion. Tennard v.
Cockrell, 317 F. 3d 476, 477 (2003). We again granted certio-
rari. 540 U. S. 945 (2003).
II
A
A COA should issue if the applicant has “made a substan-
tial 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 ju-
rists would find the district court’s assessment of the consti-
tutional 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 fur-
ther” ’ ”). The petitioner’s 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 con-
trary 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 Tennard’s 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

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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 accused’s right to be
free from cruel and unusual punishment and are also void
for vagueness.” Defendant’s Motion to Set Aside the In-
dictment in Cause No. 431127 (248th Jud. Dist. Ct. Harris
County, Tex., May 28, 1986), p. 4.
B
Despite paying lipservice to the principles guiding issu-
ance of a COA, Tennard v. Cockrell, 284 F. 3d, at 594, the
Fifth Circuit’s analysis proceeded along a distinctly different
track. Rather than examining the District Court’s 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 evi-
dence must show (1) a uniquely severe permanent handi-
cap 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.’ ” Id.,
at 595 (quoting Davis v. Scott, 51 F. 3d 457, 460–461
(CA5 1995)).
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. Cock-
rell, 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, 320–321 (2002);
Davis, supra, at 460–461. Only after the court finds that

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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 jury’s effective reach).
In Tennard v. Cockrell, the Fifth Circuit concluded that Ten-
nard was “precluded from establishing a Penry claim” be-
cause 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 Circuit’s test has no foundation in the decisions
of this Court. Neither Penry I nor its progeny screened
mitigating evidence for “constitutional relevance” before con-
sidering whether the jury instructions comported with the
Eighth Amendment. Indeed, the mitigating evidence pre-
sented in Penry I was concededly relevant, see Tr. of Oral
Arg., O. T. 1988, No. 87–6177, pp. 34–36, so even if limiting
principles regarding relevance were suggested in our opin-
ion—and we do not think they were—they could not have
been material to the holding.
When we addressed directly the relevance standard appli-
cable to mitigating evidence in capital cases in McKoy v.
North Carolina, 494 U. S. 433, 440–441 (1990), we spoke in
the most expansive terms. We established that the “mean-
ing 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 stand-
ard—“ ‘ “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 miti-
gating 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

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440 (quoting State v. McKoy, 323 N. C. 1, 55–56, 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 defendant’s mitigating evidence.
Boyde v. California, 494 U. S. 370, 377–378 (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 prof-
fers 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 circum-
stances” (quoting Eddings, supra, at 114)).
The Fifth Circuit’s test is inconsistent with these princi-
ples. Most obviously, the test will screen out any positive
aspect of a defendant’s character, because good character
traits are neither “handicap[s]” nor typically traits to which
criminal activity is “attributable.” In Skipper v. South Car-
olina, 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 sentencer’s con-
sideration.” We observed that even though the petitioner’s
evidence of good conduct in jail did “not relate specifically to
petitioner’s 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 4–5 (citation
omitted). Such evidence, we said, of “a defendant’s disposi-
tion to make a well-behaved and peaceful adjustment to life
in prison is . . . by its nature relevant to the sentencing deter-
mination.” Id., at 7. Of course, the Texas courts might

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reasonably conclude that evidence of good conduct in jail was
within the jury’s effective reach via the future dangerous-
ness special issue. See Franklin v. Lynaugh, 487 U. S. 164,
177–178 (1988) (plurality opinion); id., at 185–186 (O’Connor,
J., concurring in judgment). But under the Fifth Circuit’s
test, the evidence would have been screened out before the
time came to consider that question.
In Tennard’s 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 Tennard’s low IQ evidence, which
did “not constitute a uniquely severe condition,” with mental
retardation, a “severe permanent condition”); id., at 596–597
(concluding that Penry claims “must fail because [Tennard]
made no showing at trial that the criminal act was attribut-
able” to his condition).* Neither ground provided an ade-
quate reason to fail to reach the heart of Tennard’s Penry
claims.
We have never denied that gravity has a place in the rele-
vance analysis, insofar as evidence of a trivial feature of the
defendant’s character or the circumstances of the crime is
unlikely to have any tendency to mitigate the defendant’s
culpability. See Skipper, supra, at 7, n. 2 (“We do not hold
that all facets of the defendant’s 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
*The Fifth Circuit stated that “a majority of the Court of Criminal
Appeals found ‘no evidence in this record that [Tennard] is mentally re-
tarded.’ ” 284 F. 3d, at 596–597. 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 Tennard’s claim,” id., at 596, n. 5 (emphasis added), is
Judge Meyers’ concurring opinion.

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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 sen-
tence 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. Virginia,
536 U. S., at 316, we explained that impaired intellectual
functioning is inherently mitigating: “[T]oday our society
views mentally retarded offenders as categorically less cul-
pable than the average criminal.” Nothing in our opinion
suggested that a mentally retarded individual must establish
a nexus between her mental capacity and her crime before
the Eighth Amendment prohibition on executing her is trig-
gered. Equally, we cannot countenance the suggestion that
low IQ evidence is not relevant mitigating evidence—and
thus that the Penry question need not even be asked—unless
the defendant also establishes a nexus to the crime.
The State claims that “the Fifth Circuit’s Penry I juris-
prudence is not at issue” in this case. Brief for Respondent
35, n. 21; Tr. of Oral Arg. 33. To the contrary, that jurispru-
dence is directly at issue because the Fifth Circuit denied
Tennard relief on the ground that he did not satisfy the re-
quirements imposed by its “constitutional relevance” test.
As we have explained, the Fifth Circuit’s 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 Cir-
cuit assessed Tennard’s Penry claim under an improper legal
standard. Cf. Miller-El v. Cockrell, 537 U. S., at 341 (hold-
ing, on certiorari review of the denial of a COA, that the

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288 TENNARD v. DRETKE
Opinion of the Court
Fifth Circuit had applied an incorrect standard by improp-
erly merging the requirements of two statutory sections).
C
We turn to the analysis the Fifth Circuit should have con-
ducted: Has Tennard “demonstrate[d] that reasonable jurists
would find the district court’s assessment of the constitu-
tional 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. Evi-
dence of significantly impaired intellectual functioning is ob-
viously evidence that “might serve ‘as a basis for a sentence
less than death,’ ” Skipper, 476 U. S., at 5; see also, e. g., Wig-
gins v. Smith, 539 U. S. 510, 535 (2003) (observing, with re-
spect to individual with IQ of 79, that “Wiggins[’] . . . dimin-
ished mental capacitie[s] further augment his mitigation
case”); Burger v. Kemp, 483 U. S. 776, 779, 789, 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
petitioner’s 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 Tennard’s case was unreasonable. The relationship be-
tween the special issues and Tennard’s low IQ evidence has
the same essential features as the relationship between the
special issues and Penry’s mental retardation evidence. Im-
paired intellectual functioning has mitigating dimension be-
yond the impact it has on the individual’s ability to act delib-
erately. See Penry I, 492 U. S., at 322. A reasonable jurist
could conclude that the jury might well have given Tennard’s
low IQ evidence aggravating effect in considering his future

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289 Cite as: 542 U. S. 274 (2004)
Rehnquist, C. J., dissenting
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 he’s a danger, is the criteria to use in answering that
question.” App. 60. Indeed, the prosecutor’s comments
pressed exactly the most problematic interpretation of the
special issues, suggesting that Tennard’s low IQ was irrele-
vant in mitigation, but relevant to the question whether he
posed a future danger.
* * *
We hold that the Fifth Circuit’s “uniquely severe perma-
nent handicap” and “nexus” tests are incorrect, and we
reject them. We hold that reasonable jurists would find
debatable or wrong the District Court’s disposition of
Tennard’s low-IQ-based Penry claim, and that Tennard is
therefore entitled to a COA. 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.
Chief Justice Rehnquist, dissenting.
A certificate of appealability may only issue if the appli-
cant has “made a substantial showing of the denial of a con-
stitutional right,” 28 U. S. C. § 2253(c)(2). “Where a district
court has rejected the constitutional claims on the merits,
the showing required to satisfy § 2253(c) is straightforward:
The petitioner must demonstrate that reasonable jurists
would find the district court’s assessment of the constitu-
tional claims debatable or wrong.” Slack v. McDaniel, 529
U. S. 473, 484 (2000). Because I believe that reasonable ju-

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290 TENNARD v. DRETKE
Rehnquist, C. J., dissenting
rists would not find the District Court’s assessment of the
constitutional claims debatable or wrong, I dissent.
The District Court conducted the proper inquiry by exam-
ining whether Tennard’s evidence of low intelligence was
“within ‘the effective reach’ ” of the jury. App. 128 (quoting
Johnson v. Texas, 509 U. S. 350, 368 (1993)). And the Dis-
trict Court came to the correct result; that is, the special
issues allowed the jury to give some mitigating effect to Ten-
nard’s evidence of low intelligence. Id., at 369; Graham v.
Collins, 506 U. S. 461, 475 (1993).
In Jurek v. Texas, 428 U. S. 262 (1976), this Court held
that the Texas special issues system, as a general matter, is
constitutional. The special issues system guides the jury’s
consideration of mitigating evidence at sentencing. We
have stated:
“Although Lockett [v. Ohio, 438 U. S. 586 (1978),] and
Eddings [v. Oklahoma, 455 U. S. 104 (1982),] prevent a
State from placing relevant mitigating evidence ‘beyond
the effective reach of the sentencer,’ Graham, supra, at
475, those cases and others in that decisional line do not
bar a State from guiding the sentencer’s consideration
of mitigating evidence. Indeed, we have held that
‘there is no . . . constitutional requirement of unfettered
sentencing discretion in the jury, and States are free to
structure and shape consideration of mitigating evidence
“in an effort to achieve a more rational and equitable
administration of the death penalty.” ’ Boyde v. Cali-
fornia, 494 U. S. 370, 377 (1990) (quoting Franklin v.
Lynaugh, 487 U. S. 164, 181 (1988) (plurality opinion)).”
Johnson, supra, at 362.
In Penry v. Lynaugh, 492 U. S. 302 (1989) (Penry I), the
Court concluded that the Texas special issues were too lim-
ited to give effect to Penry’s mitigating evidence of his men-
tal retardation and severe childhood abuse. But we have
noted that Penry I did not “effec[t] a sea change in this

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291 Cite as: 542 U. S. 274 (2004)
Rehnquist, C. J., dissenting
Court’s view of the constitutionality of the former Texas
death penalty statute,” Graham, supra, at 474. Tennard’s
evidence of low intelligence simply does not present the same
difficulty that Penry’s evidence did.
There is no dispute that Tennard’s low intelligence is a
relevant mitigating circumstance, and that the sentencing
jury must be allowed to consider that mitigating evidence.
See, e. g., Eddings v. Oklahoma, 455 U. S. 104, 110 (1982)
(“ ‘[T]he sentencer . . . [may] not be precluded from consider-
ing, as a mitigating factor, any aspect of a defendant’s charac-
ter or record and any of the circumstances of the offense’ ”
(emphasis deleted) (quoting Lockett v. Ohio, 438 U. S. 586,
604 (1978))). But the Constitution does not require that
“a jury be able to give effect to mitigating evidence in every
conceivable manner in which the evidence [may] be relevant.”
Johnson, supra, at 372. The only question in this case is
whether reasonable jurists would find the District Court’s
assessment that Tennard’s evidence of low intelligence was
within the effective reach of the jury via the Texas special
issues debatable or wrong.
The Court concludes that “[t]he relationship between the
special issues and Tennard’s low IQ evidence has the same
essential features as the relationship between the special is-
sues and Penry’s mental retardation evidence.” Ante, at
288. I disagree. The first special issue asked whether Ten-
nard had caused the death of the victim “ ‘deliberately and
with the reasonable expectation that the death of the de-
ceased or another would result.’ ” Ante, at 277. As the
Court of Criminal Appeals of Texas noted and the District
Court agreed, the mitigating evidence of Tennard’s low intel-
ligence could be given effect by the jury through this deliber-
ateness special issue. It does not follow from the Court’s
conclusion in Penry I that mental retardation had relevance
to Penry’s moral culpability beyond the scope of the deliber-
ateness special issue that evidence of low intelligence has the
same relevance. And, after Johnson and Graham, it is clear

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292 TENNARD v. DRETKE
Rehnquist, C. J., dissenting
that the question is simply whether the jury could give some
effect to the mitigating evidence through the special issues.
Johnson, supra, at 369 (rejecting the petitioner’s claim that
a special instruction was necessary because his evidence of
youth had relevance outside the special issue framework);
Graham, supra, at 476–477 (“[R]eading Penry [I] as peti-
tioner urges—and thereby holding that a defendant is enti-
tled to special instructions whenever he can offer mitigating
evidence that has some arguable relevance beyond the spe-
cial issues—would be to require in all cases that a fourth
‘special issue’ be put to the jury: ‘ “Does any mitigating evi-
dence before you, whether or not relevant to the [other spe-
cial issues], lead you to believe that the death penalty should
not be imposed?” ’ The Franklin [v. Lynaugh, 487 U. S. 164
(1988),] plurality rejected precisely this contention, finding it
irreconcilable with the Court’s holding in Jurek, see Frank-
lin, supra, at 180, n. 10, and we affirm that conclusion
today”).
The second special issue asked “ ‘[i]s there a probability
that the defendant . . . would commit criminal acts of vio-
lence that would constitute a continuing threat to society?’ ”
Ante, at 277. Here, too, this case is very different from
Penry I, where there was expert medical testimony that
Penry’s condition prevented him from learning from experi-
ence. 492 U. S., at 308–309. Here, no such evidence was
presented. Given the evidence, the jury could have con-
cluded that low intelligence meant that Tennard is a slow
learner, but with the proper instruction, he could conform
his behavior to social norms. It also could have concluded,
as the Court of Criminal Appeals of Texas noted, that Ten-
nard was a “ ‘follower’ ” rather than a “ ‘leader,’ ” App. 91,
and that he again could conform his behavior in the proper
environment. In either case—contrary to Penry I—the evi-
dence could be given mitigating effect in the second special
issue. In short, low intelligence is not the same as mental

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293 Cite as: 542 U. S. 274 (2004)
Scalia, J., dissenting
retardation and does not necessarily create the Penry I
“two-edged sword.” 492 U. S., at 324. The two should not
be summarily bracketed together.
Because I do not think that reasonable jurists would dis-
agree with the District Court’s conclusion that the jury in
this case had the ability to give mitigating effect to Tennard’s
evidence of low intelligence through the first and second spe-
cial issues, I dissent.
Justice Scalia, dissenting.
Petitioner argues that Texas’s statutory special issues
framework unconstitutionally constrained the jury’s discre-
tion to give effect to his mitigating evidence of a low IQ
score, violating the requirement that “ ‘ “a sentencer must be
allowed to give full consideration and full effect to mitigat-
ing circumstances.” ’ ” Reply Brief for Petitioner 4 (quoting
Penry v. Johnson, 532 U. S. 782, 797 (2001) (Penry II), in
turn quoting Johnson v. Texas, 509 U. S. 350, 381 (1993)
(O’Connor, J., dissenting)). This claim relies on Penry v.
Lynaugh, 492 U. S. 302 (1989) (Penry I), a case that applied
principles earlier limned in Eddings v. Oklahoma, 455 U. S.
104 (1982), and Lockett v. Ohio, 438 U. S. 586 (1978).
I have previously expressed my view that this “right” to
unchanneled sentencer discretion has no basis in the Consti-
tution. See Penry I, supra, at 356–360 (opinion concurring
in part and dissenting in part). I have also said that the
Court’s decisions establishing this right do not deserve stare
decisis effect, because requiring unchanneled discretion to
say no to death cannot rationally be reconciled with our prior
decisions requiring canalized discretion to say yes. “[T]he
practice which in Furman [v. Georgia, 408 U. S. 238 (1972)
(per curiam),] had been described as the discretion to sen-
tence to death and pronounced constitutionally prohibited,
was in Woodson [v. North Carolina, 428 U. S. 280 (1976) (plu-
rality opinion),] and Lockett renamed the discretion not to

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294 TENNARD v. DRETKE
Thomas, J., dissenting
sentence to death and pronounced constitutionally required.”
Walton v. Arizona, 497 U. S. 639, 662 (1990) (Scalia, J., con-
curring in part and concurring in judgment).
The Court returned greater rationality to our Penry juris-
prudence by cutting it back in Graham v. Collins, 506 U. S.
461 (1993), and Johnson v. Texas, supra. I joined the Court
in this pruning effort, noting that “the essence of today’s
holding (to the effect that discretion may constitutionally be
channeled) was set forth in my dissent in Penry.” Id., at
374 (concurring opinion). As The Chief Justice notes, the
lower courts’ disposition of petitioner’s Penry claim in the
present case was entirely appropriate under these cases.
Ante, at 290–293 (dissenting opinion). Yet the opinion for
the Court does not even acknowledge their existence. It
finds failings in the Fifth Circuit’s framework for analyzing
Penry claims as if this Court’s own jurisprudence were not
the root of the problem. “The simultaneous pursuit of con-
tradictory objectives necessarily produces confusion.” Wal-
ton, supra, at 667.
Although the present case involves only a certificate of ap-
pealability (COA) ruling, rather than a ruling directly on the
merits of petitioner’s claim, I cannot require the issuance of
a COA when the insubstantial right at issue derives from
case law in which this Court has long left the Constitution
behind and embraced contradiction. I respectfully dissent.
Justice Thomas, dissenting.
Petitioner must rely on Penry v. Lynaugh, 492 U. S. 302
(1989), to argue that Texas’ special issues framework uncon-
stitutionally limited the discretion of his sentencing jury.
I have long maintained, however, that Penry did “so much
violence to so many of this Court’s settled precedents in an
area of fundamental constitutional law, [that] it cannot com-
mand the force of stare decisis.” Graham v. Collins, 506
U. S. 461, 497 (1993) (concurring opinion). I therefore agree
with Justice Scalia that a certificate of appealability can-

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Thomas, J., dissenting
not be issued based upon an “insubstantial right . . . derive[d]
from case law in which this Court has long left the Constitu-
tion behind and embraced contradiction.” Ante, at 294 (dis-
senting opinion). I respectfully dissent.