Justice O’Connor, dissenting.
The Court’s decision today establishes a categorical rule forbidding the execution of any offender for any crime committed before his 18th birthday, no matter how deliberate, wanton, or cruel the offense. Neither the objective evidence of contemporary societal values, nor the Court’s moral proportionality analysis, nor the two in tandem suffice to justify this ruling.
Although the Court finds support for its decision in the fact that a majority of the States now disallow capital punishment of 17-year-old offenders, it refrains from asserting that its holding is compelled by a genuine national consensus. Indeed, the evidence before us fails to demonstrate conclusively that any such consensus has emerged in the brief period since we upheld the constitutionality of this practice in Stanford v. Kentucky, 492 U. S. 361 (1989).
Instead, the rule decreed by the Court rests, ultimately, on its independent moral judgment that death is a disproportionately severe punishment for any 17-year-old offender. I do not subscribe to this judgment. Adolescents as a class are undoubtedly less mature, and therefore less culpable for their misconduct, than adults. But the Court has adduced no evidence impeaching the seemingly reasonable conclusion reached by many state legislatures: that at least some 17-year-old murderers are sufficiently mature to deserve the death penalty in an appropriate case. Nor has it been shown that capital sentencing juries are incapable of accurately assessing a youthful defendant’s maturity or of giving due weight to the mitigating characteristics associated with youth.
On this record—and especially in light of the fact that so little has changed since our recent decision in Stanford —I would not substitute our judgment about the moral propriety of capital punishment for 17-year-old murderers for the judgments of the Nation’s legislatures. Rather, I would demand a clearer showing that our society truly has set its face against this practice before reading the Eighth Amendment categorically to forbid it.
I
A
Let me begin by making clear that I agree with much of the Court’s description of the general principles that guide our Eighth Amendment jurisprudence. The Amendment bars not only punishments that are inherently “ ‘barbaric,’ ” but also those that are “ ‘ excessive’ in relation to the crime committed. ” Coker v. Georgia, 433 U. S. 584, 592 (1977) (plurality opinion). A sanction is therefore beyond the state’s authority to inflict if it makes “no measurable contribution” to acceptable penal goals or is “grossly out of proportion to the severity of the crime.” Ibid. The basic “precept of justice that punishment for crime should be … proportioned to [the] offense,” Weems v. United States, 217 U. S. 349, 367 (1910), applies with special force to the death penalty. In capital cases, the Constitution demands that the punishment be tailored both to the nature of the crime itself and to the defendant’s “personal responsibility and moral guilt.” Enmund v. Florida, 458 U. S. 782, 801 (1982); see also id., at 825 (O’Connor, J., dissenting); Tison v. Arizona, 481 U. S. 137, 149 (1987); Eddings v. Oklahoma, 455 U. S. 104, 111–112 (1982).
It is by now beyond serious dispute that the Eighth Amendment’s prohibition of “cruel and unusual punishments” is not a static command. Its mandate would be little more than a dead letter today if it barred only those sanctions—like the execution of children under the age of seven—that civilized society had already repudiated in 1791. See ante, at 1 (Stevens, J., concurring); cf. Stanford, supra, at 368 (discussing the common law rule at the time the Bill of Rights was adopted). Rather, because “[t]he basic concept underlying the Eighth Amendment is nothing less than the dignity of man,” the Amendment “must draw its meaning from the evolving standards of decency that mark the progress of a maturing society.” Trop v. Dulles, 356 U. S. 86, 100–101 (1958) (plurality opinion). In discerning those standards, we look to “objective factors to the maximum possible extent.” Coker, supra, at 592 (plurality opinion). Laws enacted by the Nation’s legislatures provide the “clearest and most reliable objective evidence of contemporary values.” Penry v. Lynaugh, 492 U. S. 302, 331 (1989). And data reflecting the actions of sentencing juries, where available, can also afford “ ‘a significant and reliable objective index’ ” of societal mores. Coker, supra, at 596 (plurality opinion) (quoting Gregg v. Georgia, 428 U. S. 153, 181 (1976)) (joint opinion of Stewart, Powell, and Stevens, JJ.).
Although objective evidence of this nature is entitled to great weight, it does not end our inquiry. Rather, as the Court today reaffirms, see ante, at 9, 20–21, “the Constitution contemplates that in the end our own judgment will be brought to bear on the question of the acceptability of the death penalty under the Eighth Amendment.” Coker, supra, at 597 (plurality opinion). “[P]roportionality—at least as regards capital punishment—not only requires an inquiry into contemporary standards as expressed by legislators and jurors, but also involves the notion that the magnitude of the punishment imposed must be related to the degree of the harm inflicted on the victim, as well as to the degree of the defendant’s blameworthiness.” Enmund, supra, at 815 (O’Connor, J., dissenting). We therefore have a “constitutional obligation” to judge for ourselves whether the death penalty is excessive punishment for a particular offense or class of offenders. See Stanford, 492 U. S., at 382 (O’Connor, J., concurring in part and concurring in judgment); see also Enmund, supra, at 797 (“[I]t is for us ultimately to judge whether the Eighth Amendment permits imposition of the death penalty”).
B
Twice in the last two decades, the Court has applied these principles in deciding whether the Eighth Amendment permits capital punishment of adolescent offenders. In Thompson v. Oklahoma, 487 U. S. 815 (1988), a plurality of four Justices concluded that the Eighth Amendment barred capital punishment of an offender for a crime committed before the age of 16. I concurred in that judgment on narrower grounds. At the time, 32 state legislatures had “definitely concluded that no 15-year-old should be exposed to the threat of execution,” and no legislature had affirmatively endorsed such a practice. Id., at 849 (O’Connor, J., concurring in judgment). While acknowledging that a national consensus forbidding the execution of 15-year-old offenders “very likely” did exist, I declined to adopt that conclusion as a matter of constitutional law without clearer evidentiary support. Ibid. Nor, in my view, could the issue be decided based on moral proportionality arguments of the type advanced by the Court today. Granting the premise “that adolescents are generally less blameworthy than adults who commit similar crimes,” I wrote, “it does not necessarily follow that all 15-year-olds are incapable of the moral culpability that would justify the imposition of capital punishment.” Id., at 853. Similarly, we had before us no evidence “that 15-year-olds as a class are inherently incapable of being deterred from major crimes by the prospect of the death penalty.” Ibid. I determined instead that, in light of the strong but inconclusive evidence of a national consensus against capital punishment of under-16 offenders, concerns rooted in the Eighth Amendment required that we apply a clear statement rule. Because the capital punishment statute in Thompson did not specify the minimum age at which commission of a capital crime would be punishable by death, I concluded that the statute could not be read to authorize the death penalty for a 15-year-old offender. Id., at 857–858.
The next year, in Stanford v. Kentucky, supra, the Court held that the execution of 16or 17-year-old capital murderers did not violate the Eighth Amendment. I again wrote separately, concurring in part and concurring in the judgment. At that time, 25 States did not permit the execution of under-18 offenders, including 13 that lacked the death penalty altogether. See id., at 370. While noting that “[t]he day may come when there is such general legislative rejection of the execution of 16or 17-year-old capital murderers that a clear national consensus can be said to have developed,” I concluded that that day had not yet arrived. Id., at 381–382 (opinion concurring in part and concurring in judgment). I reaffirmed my view that, beyond assessing the actions of legislatures and juries, the Court has a constitutional obligation to judge for itself whether capital punishment is a proportionate response to the defendant’s blameworthiness. Id., at 382. Nevertheless, I concluded that proportionality arguments similar to those endorsed by the Court today did not justify a categorical Eighth Amendment rule against capital punishment of 16and 17-year-old offenders. See ibid. (citing Thompson, supra, at 853–854 (O’Connor, J., concurring in judgment)).
The Court has also twice addressed the constitutionality of capital punishment of mentally retarded offenders. In Penry v. Lynaugh, 492 U. S. 302 (1989), decided the same year as Stanford, we rejected the claim that the Eighth Amendment barred the execution of the mentally retarded. At that time, only two States specifically prohibited the practice, while 14 others did not have capital punishment at all. 492 U. S., at 334. Much had changed when we revisited the question three Terms ago in Atkins v. Virginia, 536 U. S. 304 (2002). In Atkins, the Court reversed Penry and held that the Eighth Amendment forbids capital punishment of mentally retarded offenders. 536 U. S., at 321. In the 13 years between Penry and Atkins, there had been a wave of legislation prohibiting the execution of such offenders. By the time we heard Atkins, 30 States barred the death penalty for the mentally retarded, and even among those States theoretically permitting such punishment, very few had executed a mentally retarded offender in recent history. 536 U. S., at 314–316. On the basis of this evidence, the Court determined that it was “fair to say that a national consensus ha[d] developed against” the practice. Id., at 316.
But our decision in Atkins did not rest solely on this tentative conclusion. Rather, the Court’s independent moral judgment was dispositive. The Court observed that mentally retarded persons suffer from major cognitive and behavioral deficits, i.e., “subaverage intellectual functioning” and “significant limitations in adaptive skills such as communication, self-care, and self-direction that became manifest before age 18.” Id., at 318. “Because of their impairments, [such persons] by definition … have diminished capacities to understand and process information, to communicate, to abstract from mistakes and learn from experience, to engage in logical reasoning, to control impulses, and to understand the reactions of others.” Ibid. We concluded that these deficits called into serious doubt whether the execution of mentally retarded offenders would measurably contribute to the principal penological goals that capital punishment is intended to serve—retribution and deterrence. Id., at 319–321. Mentally retarded offenders’ impairments so diminish their personal moral culpability that it is highly unlikely that such offenders could ever deserve the ultimate punishment, even in cases of capital murder. Id., at 319. And these same impairments made it very improbable that the threat of the death penalty would deter mentally retarded persons from committing capital crimes. Id., at 319–320. Having concluded that capital punishment of the mentally retarded is inconsistent with the Eighth Amendment, the Court “ ‘le[ft] to the State[s] the task of developing appropriate ways to enforce the constitutional restriction upon [their] execution of sentences.’ ” Id., at 317 (quoting Ford v. Wainwright, 477 U. S. 399, 416–417 (1986)).
II
A
Although the general principles that guide our Eighth Amendment jurisprudence afford some common ground, I part ways with the Court in applying them to the case before us. As a preliminary matter, I take issue with the Court’s failure to reprove, or even to acknowledge, the Supreme Court of Missouri’s unabashed refusal to follow our controlling decision in Stanford. The lower court concluded that, despite Stanford ’s clear holding and historical recency, our decision was no longer binding authority because it was premised on what the court deemed an obsolete assessment of contemporary values. Quite apart from the merits of the constitutional question, this was clear error.
Because the Eighth Amendment “draw[s] its meaning from … evolving standards of decency,” Trop, 356 U. S., at 101 (plurality opinion), significant changes in societal mores over time may require us to reevaluate a prior decision. Nevertheless, it remains “ this Court’s prerogative alone to overrule one of its precedents.” State Oil Co. v. Khan, 522 U. S. 3, 20 (1997) (emphasis added). That is so even where subsequent decisions or factual developments may appear to have “significantly undermined” the rationale for our earlier holding. United States v. Hatter, 532 U. S. 557, 567 (2001); see also State Oil Co., supra, at 20; Rodriguez de Quijas v. Shearson/American Express, Inc., 490 U. S. 477, 484 (1989). The Eighth Amendment provides no exception to this rule. On the contrary, clear, predictable, and uniform constitutional standards are especially desirable in this sphere. By affirming the lower court’s judgment without so much as a slap on the hand, today’s decision threatens to invite frequent and disruptive reassessments of our Eighth Amendment precedents.
B
In determining whether the juvenile death penalty comports with contemporary standards of decency, our inquiry begins with the “clearest and most reliable objective evidence of contemporary values”—the actions of the Nation’s legislatures. Penry, supra, at 331. As the Court emphasizes, the overall number of jurisdictions that currently disallow the execution of under-18 offenders is the same as the number that forbade the execution of mentally retarded offenders when Atkins was decided. Ante, at 10. At present, 12 States and the District of Columbia do not have the death penalty, while an additional 18 States and the Federal Government authorize capital punishment but prohibit the execution of under-18 offenders. See ante, at 27–28 (Appendix A). And here, as in Atkins, only a very small fraction of the States that permit capital punishment of offenders within the relevant class has actually carried out such an execution in recent history: Six States have executed under-18 offenders in the 16 years since Stanford, while five States had executed mentally retarded offenders in the 13 years prior to Atkins. See Atkins, 536 U. S., at 316; V. Streib, The Juvenile Death Penalty Today: Death Sentences and Executions for Juvenile Crimes, January 1, 1973–December 31, 2004, No. 76, pp. 15–23 (2005), available at http://www.law.onu.edu/faculty/streib/documents/Juv DeathDec2004.pdf (last updated Jan. 31, 2005) (as visited Feb. 25, 2005, and available in the Clerk of the Court’s case file) (hereinafter Streib). In these respects, the objective evidence in this case is, indeed, “similar, and in some respects parallel to” the evidence upon which we relied in Atkins. Ante, at 10.
While the similarities between the two cases are undeniable, the objective evidence of national consensus is marginally weaker here. Most importantly, in Atkins there was significant evidence of opposition to the execution of the mentally retarded, but there was virtually no countervailing evidence of affirmative legislative support for this practice. Cf. Thompson, 487 U. S., at 849 (O’Connor, J., concurring in judgment) (attributing significance to the fact that “no legislature in this country has affirmatively and unequivocally endorsed” capital punishment of 15-year-old offenders). The States that permitted such executions did so only because they had not enacted any prohibitory legislation. Here, by contrast, at least eight States have current statutes that specifically set 16 or 17 as the minimum age at which commission of a capital crime can expose the offender to the death penalty. See ante, at 26 (Appendix A).* Five of these eight States presently have one or more juvenile offenders on death row (six if respondent is included in the count), see Streib 24–31, and four of them have executed at least one under-18 offender in the past 15 years, see id., at 15–23. In all, there are currently over 70 juvenile offenders on death row in 12 different States (13 including respondent). See id., at 11, 24–31. This evidence suggests some measure of continuing public support for the availability of the death penalty for 17-year-old capital murderers.
Moreover, the Court in Atkins made clear that it was “not so much the number of [States forbidding execution of the mentally retarded] that [was] significant, but the consistency of the direction of change.” 536 U. S., at 315. In contrast to the trend in Atkins, the States have not moved uniformly towards abolishing the juvenile death penalty. Instead, since our decision in Stanford, two States have expressly reaffirmed their support for this practice by enacting statutes setting 16 as the minimum age for capital punishment. See Mo. Rev. Stat. §565.020.2 (2000); Va. Code Ann. §18.2–10(a) (Lexis 2004). Furthermore, as the Court emphasized in Atkins itself, 536 U. S., at 315, n. 18, the pace of legislative action in this context has been considerably slower than it was with regard to capital punishment of the mentally retarded. In the 13 years between our decisions in Penry and Atkins, no fewer than 16 States banned the execution of mentally retarded offenders. See Atkins, supra, at 314–315. By comparison, since our decision 16 years ago in Stanford, only four States that previously permitted the execution of under-18 offenders, plus the Federal Government, have legistlatively reversed course, and one additional State’s high court has construed the State’s death penalty statute not to apply to under-18 offenders, see State v. Furman, 122 Wash. 2d 440, 458, 858 P. 2d 1092, 1103 (1993) (en banc). The slower pace of change is no doubt partially attributable, as the Court says, to the fact that 11 States had already imposed a minimum age of 18 when Stanford was decided. See ante, at 12–13. Nevertheless, the extraordinary wave of legislative action leading up to our decision in Atkins provided strong evidence that the country truly had set itself against capital punishment of the mentally retarded. Here, by contrast, the halting pace of change gives reason for pause.
To the extent that the objective evidence supporting today’s decision is similar to that in Atkins, this merely highlights the fact that such evidence is not dispositive in either of the two cases. After all, as the Court today confirms, ante, at 9, 20–21, the Constitution requires that “ ‘in the end our own judgment … be brought to bear’ ” in deciding whether the Eighth Amendment forbids a particular punishment. Atkins, supra, at 312 (quoting Coker, 433 U. S., at 597 (plurality opinion)). This judgment is not merely a rubber stamp on the tally of legislative and jury actions. Rather, it is an integral part of the Eighth Amendment inquiry—and one that is entitled to independent weight in reaching our ultimate decision.
Here, as in Atkins, the objective evidence of a national consensus is weaker than in most prior cases in which the Court has struck down a particular punishment under the Eighth Amendment. See Coker, supra, at 595–596 (plurality opinion) (striking down death penalty for rape of an adult woman, where only one jurisdiction authorized such punishment); Enmund, 458 U. S., at 792 (striking down death penalty for certain crimes of aiding and abetting felony-murder, where only eight jurisdictions authorized such punishment); Ford v. Wainwright, 477 U. S., at 408 (striking down capital punishment of the insane, where no jurisdiction permitted this practice). In my view, the objective evidence of national consensus, standing alone, was insufficient to dictate the Court’s holding in Atkins. Rather, the compelling moral proportionality argument against capital punishment of mentally retarded offenders played a decisive role in persuading the Court that the practice was inconsistent with the Eighth Amendment. Indeed, the force of the proportionality argument in Atkins significantly bolstered the Court’s confidence that the objective evidence in that case did, in fact, herald the emergence of a genuine national consensus. Here, by contrast, the proportionality argument against the juvenile death penalty is so flawed that it can be given little, if any, analytical weight—it proves too weak to resolve the lingering ambiguities in the objective evidence of legislative consensus or to justify the Court’s categorical rule.
C
Seventeen-year-old murderers must be categorically exempted from capital punishment, the Court says, because they “cannot with reliability be classified among the worst offenders.” Ante, at 15. That conclusion is premised on three perceived differences between “adults,” who have already reached their 18th birthdays, and “juveniles,” who have not. See ante, at 15–16. First, juveniles lack maturity and responsibility and are more reckless than adults. Second, juveniles are more vulnerable to outside influences because they have less control over their surroundings. And third, a juvenile’s character is not as fully formed as that of an adult. Based on these characteristics, the Court determines that 17-year-old capital murderers are not as blameworthy as adults guilty of similar crimes; that 17-year-olds are less likely than adults to be deterred by the prospect of a death sentence; and that it is difficult to conclude that a 17-year-old who commits even the most heinous of crimes is “irretrievably depraved.” Ante, at 16–18. The Court suggests that “a rare case might arise in which a juvenile offender has sufficient psychological maturity, and at the same time demonstrates sufficient depravity, to merit a sentence of death.” Ante, at 18. However, the Court argues that a categorical age-based prohibition is justified as a prophylactic rule because “[t]he differences between juvenile and adult offenders are too marked and well understood to risk allowing a youthful person to receive the death penalty despite insufficient culpability.” Ante, at 19.
It is beyond cavil that juveniles as a class are generally less mature, less responsible, and less fully formed than adults, and that these differences bear on juveniles’ comparative moral culpability. See, e.g., Johnson v. Texas, 509 U. S. 350, 367 (1993) (“There is no dispute that a defendant’s youth is a relevant mitigating circumstance”); id., at 376 (O’Connor, J., dissenting) (“[T]he vicissitudes of youth bear directly on the young offender’s culpability and responsibility for the crime”); Eddings, 455 U. S., at 115–116 (“Our history is replete with laws and judicial recognition that minors, especially in their earlier years, generally are less mature and responsible than adults”). But even accepting this premise, the Court’s proportionality argument fails to support its categorical rule.
First, the Court adduces no evidence whatsoever in support of its sweeping conclusion, see ante, at 18, that it is only in “rare” cases, if ever, that 17-year-old murderers are sufficiently mature and act with sufficient depravity to warrant the death penalty. The fact that juveniles are generally less culpable for their misconduct than adults does not necessarily mean that a 17-year-old murderer cannot be sufficiently culpable to merit the death penalty. At most, the Court’s argument suggests that the average 17-year-old murderer is not as culpable as the average adult murderer. But an especially depraved juvenile offender may nevertheless be just as culpable as many adult offenders considered bad enough to deserve the death penalty. Similarly, the fact that the availability of the death penalty may be less likely to deter a juvenile from committing a capital crime does not imply that this threat cannot effectively deter some 17-year-olds from such an act. Surely there is an age below which no offender, no matter what his crime, can be deemed to have the cognitive or emotional maturity necessary to warrant the death penalty. But at least at the margins between adolescence and adulthood—and especially for 17-year-olds such as respondent—the relevant differences between “adults” and “juveniles” appear to be a matter of degree, rather than of kind. It follows that a legislature may reasonably conclude that at least some 17-year-olds can act with sufficient moral culpability, and can be sufficiently deterred by the threat of execution, that capital punishment may be warranted in an appropriate case.
Indeed, this appears to be just such a case. Christopher Simmons’ murder of Shirley Crook was premeditated, wanton, and cruel in the extreme. Well before he committed this crime, Simmons declared that he wanted to kill someone. On several occasions, he discussed with two friends (ages 15 and 16) his plan to burglarize a house and to murder the victim by tying the victim up and pushing him from a bridge. Simmons said they could “ ‘get away with it’ ” because they were minors. Brief for Petitioners 3. In accord with this plan, Simmons and his 15-year-old accomplice broke into Mrs. Crook’s home in the middle of the night, forced her from her bed, bound her, and drove her to a state park. There, they walked her to a railroad trestle spanning a river, “hog-tied” her with electrical cable, bound her face completely with duct tape, and pushed her, still alive, from the trestle. She drowned in the water below. Id., at 4. One can scarcely imagine the terror that this woman must have suffered throughout the ordeal leading to her death. Whatever can be said about the comparative moral culpability of 17-year-olds as a general matter, Simmons’ actions unquestionably reflect “ ‘a consciousness materially more “depraved” than that of’ … the average murderer.” See Atkins, 536 U. S., at 319 (quoting Godfrey v. Georgia, 446 U. S. 420, 433 (1980)). And Simmons’ prediction that he could murder with impunity because he had not yet turned 18—though inaccurate—suggests that he did take into account the perceived risk of punishment in deciding whether to commit the crime. Based on this evidence, the sentencing jury certainly had reasonable grounds for concluding that, despite Simmons’ youth, he “ha[d] sufficient psychological maturity” when he committed this horrific murder, and “at the same time demonstrate[d] sufficient depravity, to merit a sentence of death.” See ante, at 18.
The Court’s proportionality argument suffers from a second and closely related defect: It fails to establish that the differences in maturity between 17-year-olds and young “adults” are both universal enough and significant enough to justify a bright-line prophylactic rule against capital punishment of the former. The Court’s analysis is premised on differences in the aggregate between juveniles and adults, which frequently do not hold true when comparing individuals. Although it may be that many 17-year-old murderers lack sufficient maturity to deserve the death penalty, some juvenile murderers may be quite mature. Chronological age is not an unfailing measure of psychological development, and common experience suggests that many 17-year-olds are more mature than the average young “adult.” In short, the class of offenders exempted from capital punishment by today’s decision is too broad and too diverse to warrant a categorical prohibition. Indeed, the age-based line drawn by the Court is indefensibly arbitrary—it quite likely will protect a number of offenders who are mature enough to deserve the death penalty and may well leave vulnerable many who are not.
For purposes of proportionality analysis, 17-year-olds as a class are qualitatively and materially different from the mentally retarded. “Mentally retarded” offenders, as we understood that category in Atkins, are defined by precisely the characteristics which render death an excessive punishment. A mentally retarded person is, “by definition,” one whose cognitive and behavioral capacities have been proven to fall below a certain minimum. See Atkins, 536 U. S., at 318; see also id., at 308, n. 3 (discussing characteristics of mental retardation); id., at 317, and n. 22 (leaving to the States the development of mechanisms to determine which offenders fall within the class exempt from capital punishment). Accordingly, for purposes of our decision in Atkins, the mentally retarded are not merely less blameworthy for their misconduct or less likely to be deterred by the death penalty than others. Rather, a mentally retarded offender is one whose demonstrated impairments make it so highly unlikely that he is culpable enough to deserve the death penalty or that he could have been deterred by the threat of death, that execution is not a defensible punishment. There is no such inherent or accurate fit between an offender’s chronological age and the personal limitations which the Court believes make capital punishment excessive for 17-year-old murderers. Moreover, it defies common sense to suggest that 17-year-olds as a class are somehow equivalent to mentally retarded persons with regard to culpability or susceptibility to deterrence. Seventeen-year-olds may, on average, be less mature than adults, but that lesser maturity simply cannot be equated with the major, lifelong impairments suffered by the mentally retarded.
The proportionality issues raised by the Court clearly implicate Eighth Amendment concerns. But these concerns may properly be addressed not by means of an arbitrary, categorical age-based rule, but rather through individualized sentencing in which juries are required to give appropriate mitigating weight to the defendant’s immaturity, his susceptibility to outside pressures, his cognizance of the consequences of his actions, and so forth. In that way the constitutional response can be tailored to the specific problem it is meant to remedy. The Eighth Amendment guards against the execution of those who are “insufficiently culpable,” see ante, at 19, in significant part, by requiring sentencing that “reflect[s] a reasoned moral response to the defendant’s background, character, and crime.” California v. Brown, 479 U. S. 538, 545 (1987) (O’Connor, J., concurring). Accordingly, the sentencer in a capital case must be permitted to give full effect to all constitutionally relevant mitigating evidence. See Tennard v. Dretke, 542 U. S. ___, ___ (2004) (slip op., at 9–10); Lockett v. Ohio, 438 U. S. 586, 604 (1978) (plurality opinion). A defendant’s youth or immaturity is, of course, a paradigmatic example of such evidence. See Eddings, 455 U. S., at 115–116.
Although the prosecutor’s apparent attempt to use respondent’s youth as an aggravating circumstance in this case is troubling, that conduct was never challenged with specificity in the lower courts and is not directly at issue here. As the Court itself suggests, such “overreaching” would best be addressed, if at all, through a more narrowly tailored remedy. See ante, at 19. The Court argues that sentencing juries cannot accurately evaluate a youthful offender’s maturity or give appropriate weight to the mitigating characteristics related to youth. But, again, the Court presents no real evidence—and the record appears to contain none—supporting this claim. Perhaps more importantly, the Court fails to explain why this duty should be so different from, or so much more difficult than, that of assessing and giving proper effect to any other qualitative capital sentencing factor. I would not be so quick to conclude that the constitutional safeguards, the sentencing juries, and the trial judges upon which we place so much reliance in all capital cases are inadequate in this narrow context.
D
I turn, finally, to the Court’s discussion of foreign and international law. Without question, there has been a global trend in recent years towards abolishing capital punishment for under-18 offenders. Very few, if any, countries other than the United States now permit this practice in law or in fact. See ante, at 22–23. While acknowledging that the actions and views of other countries do not dictate the outcome of our Eighth Amendment inquiry, the Court asserts that “the overwhelming weight of international opinion against the juvenile death penalty … does provide respected and significant confirmation for [its] own conclusions.” Ante, at 24. Because I do not believe that a genuine national consensus against the juvenile death penalty has yet developed, and because I do not believe the Court’s moral proportionality argument justifies a categorical, age-based constitutional rule, I can assign no such confirmatory role to the international consensus described by the Court. In short, the evidence of an international consensus does not alter my determination that the Eighth Amendment does not, at this time, forbid capital punishment of 17-year-old murderers in all cases.
Nevertheless, I disagree with Justice Scalia’s contention, post, at 15–22 (dissenting opinion), that foreign and international law have no place in our Eighth Amendment jurisprudence. Over the course of nearly half a century, the Court has consistently referred to foreign and international law as relevant to its assessment of evolving standards of decency. See Atkins, 536 U. S., at 317, n. 21; Thompson, 487 U. S., at 830–831, and n. 31 (plurality opinion); Enmund, 458 U. S., at 796–797, n. 22; Coker, 433 U. S., at 596, n. 10 (plurality opinion); Trop, 356 U. S., at 102–103 (plurality opinion). This inquiry reflects the special character of the Eighth Amendment, which, as the Court has long held, draws its meaning directly from the maturing values of civilized society. Obviously, American law is distinctive in many respects, not least where the specific provisions of our Constitution and the history of its exposition so dictate. Cf. post, at 18–19 (Scalia, J., dissenting) (discussing distinctively American rules of law related to the Fourth Amendment and the Establishment Clause). But this Nation’s evolving understanding of human dignity certainly is neither wholly isolated from, nor inherently at odds with, the values prevailing in other countries. On the contrary, we should not be surprised to find congruence between domestic and international values, especially where the international community has reached clear agreement—expressed in international law or in the domestic laws of individual countries—that a particular form of punishment is inconsistent with fundamental human rights. At least, the existence of an international consensus of this nature can serve to confirm the reasonableness of a consonant and genuine American consensus. The instant case presents no such domestic consensus, however, and the recent emergence of an otherwise global consensus does not alter that basic fact.
***
In determining whether the Eighth Amendment permits capital punishment of a particular offense or class of offenders, we must look to whether such punishment is consistent with contemporary standards of decency. We are obligated to weigh both the objective evidence of societal values and our own judgment as to whether death is an excessive sanction in the context at hand. In the instant case, the objective evidence is inconclusive; standing alone, it does not demonstrate that our society has repudiated capital punishment of 17-year-old offenders in all cases. Rather, the actions of the Nation’s legislatures suggest that, although a clear and durable national consensus against this practice may in time emerge, that day has yet to arrive. By acting so soon after our decision in Stanford, the Court both pre-empts the democratic debate through which genuine consensus might develop and simultaneously runs a considerable risk of inviting lower court reassessments of our Eighth Amendment precedents.
To be sure, the objective evidence supporting today’s decision is similar to (though marginally weaker than) the evidence before the Court in Atkins. But Atkins could not have been decided as it was based solely on such evidence. Rather, the compelling proportionality argument against capital punishment of the mentally retarded played a decisive role in the Court’s Eighth Amendment ruling. Moreover, the constitutional rule adopted in Atkins was tailored to this proportionality argument: It exempted from capital punishment a defined group of offenders whose proven impairments rendered it highly unlikely, and perhaps impossible, that they could act with the degree of culpability necessary to deserve death. And Atkins left to the States the development of mechanisms to determine which individual offenders fell within this class.
In the instant case, by contrast, the moral proportionality arguments against the juvenile death penalty fail to support the rule the Court adopts today. There is no question that “the chronological age of a minor is itself a relevant mitigating factor of great weight,” Eddings, 455 U. S., at 116, and that sentencing juries must be given an opportunity carefully to consider a defendant’s age and maturity in deciding whether to assess the death penalty. But the mitigating characteristics associated with youth do not justify an absolute age limit. A legislature can reasonably conclude, as many have, that some 17-year-old murderers are mature enough to deserve the death penalty in an appropriate case. And nothing in the record before us suggests that sentencing juries are so unable accurately to assess a 17-year-old defendant’s maturity, or so incapable of giving proper weight to youth as a mitigating factor, that the Eighth Amendment requires the bright-line rule imposed today. In the end, the Court’s flawed proportionality argument simply cannot bear the weight the Court would place upon it.
Reasonable minds can differ as to the minimum age at which commission of a serious crime should expose the defendant to the death penalty, if at all. Many jurisdictions have abolished capital punishment altogether, while many others have determined that even the most heinous crime, if committed before the age of 18, should not be punishable by death. Indeed, were my office that of a legislator, rather than a judge, then I, too, would be inclined to support legislation setting a minimum age of 18 in this context. But a significant number of States, including Missouri, have decided to make the death penalty potentially available for 17-year-old capital murderers such as respondent. Without a clearer showing that a genuine national consensus forbids the execution of such offenders, this Court should not substitute its own “inevitably subjective judgment” on how best to resolve this difficult moral question for the judgments of the Nation’s democratically elected legislatures. See Thompson, supra, at 854 (O’Connor, J., concurring in judgment). I respectfully dissent.
Notes
* In 12 other States that have capital punishment, under-18 offenders can be subject to the death penalty as a result of transfer statutes that permit such offenders to be tried as adults for certain serious crimes. See ante, at 26 (Appendix A). As I observed in Thompson v. Oklahoma, 487 U. S. 815, 850–852 (1988) (opinion concurring in judgment): “There are many reasons, having nothing whatsoever to do with capital punishment, that might motivate a legislature to provide as a general matter for some [minors] to be channeled into the adult criminal justice process.” Accordingly, while these 12 States clearly cannot be counted as opposing capital punishment of under-18 offenders, the fact that they permit such punishment through this indirect mechanism does not necessarily show affirmative and unequivocal legislative support for the practice. See ibid.