Cite as: 536 U. S. 304 (2002)
Opinion of the Court
a basis for the death penalty applies to mentally retarded offenders. Gregg v. Georgia, 428 U. S. 153, 183 (1976) ( joint opinion of Stewart, Powell, and Stevens, JJ.), identified "retribution and deterrence of capital crimes by prospective offenders" as the social purposes served by the death penalty. Unless the imposition of the death penalty on a mentally retarded person "measurably contributes to one or both of these goals, it 'is nothing more than the purposeless and needless imposition of pain and suffering,' and hence an unconstitutional punishment." Enmund, 458 U. S., at 798.
With respect to retribution—the interest in seeing that the offender gets his "just deserts"—the severity of the appropriate punishment necessarily depends on the culpability of the offender. Since Gregg, our jurisprudence has consistently confined the imposition of the death penalty to a narrow category of the most serious crimes. For example, in Godfrey v. Georgia, 446 U. S. 420 (1980), we set aside a death sentence because the petitioner's crimes did not reflect "a consciousness materially more 'depraved' than that of any person guilty of murder." Id., at 433. If the culpability of the average murderer is insufficient to justify the most extreme sanction available to the State, the lesser culpability of the mentally retarded offender surely does not merit that form of retribution. Thus, pursuant to our narrowing jurisprudence, which seeks to ensure that only the most deserving of execution are put to death, an exclusion for the mentally retarded is appropriate.
With respect to deterrence—the interest in preventing capital crimes by prospective offenders—"it seems likely that 'capital punishment can serve as a deterrent only when murder is the result of premeditation and deliberation,' " Enmund, 458 U. S., at 799. Exempting the mentally retarded from that punishment will not affect the "cold calculus that precedes the decision" of other potential murderers. Gregg, 428 U. S., at 186. Indeed, that sort of calculus is at the opposite end of the spectrum from behavior of mentally retarded
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