In Atkins v. Virginia, 536 U. S. 304 , this Court held that the Eighth Amendment bars execution of mentally retarded offenders. Prior to Atkins, mental retardation merited consideration as a mitigating factor, but did not bar imposition of the death penalty. See Penry v. Lynaugh, 492 U. S. 302 . Nearly a decade before Atkins, respondent Bies was tried and convicted in Ohio of the aggravated murder, kidnapping, and attempted rape of a ten-year-old boy. Instructed at the sentencing stage to weigh mitigating circumstances (including evidence of Bies’ mild to borderline mental retardation) against aggravating factors (including the crime’s brutality), the jury recommended a death sentence, which the trial court imposed. Ohio’s Court of Appeals and Supreme Court affirmed the conviction and sentence, each concluding that Bies’ mental retardation was entitled to “some weight” as a mitigating factor, but that the aggravating circumstances outweighed the mitigating circumstances. Bies then filed an unsuccessful petition for state postconviction relief, contending for the first time that the Eighth Amendment prohibits execution of a mentally retarded defendant. Soon after Bies sought federal habeas relief, this Court decided Atkins. The opinion left to the States the task of developing appropriate ways to determine when a person claiming mental retardation would fall within Atkins’ compass. Ohio heeded Atkins’ call in State v. Lott. The District Court then stayed Bies’ federal habeas proceedings so that he could present an Atkins claim to the state postconviction court. Observing that Bies’ mental retardation had not previously been established under the Atkins-Lott framework, the state court denied Bies’ motion for summary judgment and ordered a full hearing on the Atkins claim. Rather than proceeding with that hearing, Bies returned to federal court, arguing that the Double Jeopardy Clause barred the State from relitigating the mental retardation issue. The District Court granted the habeas petition, and the Sixth Circuit affirmed. Relying on Ashe v. Swenson, 397 U. S. 436 , the Court of Appeals determined that all requirements for the issue preclusion component of the Double Jeopardy Clause were met in Bies’ case. It concluded, inter alia, that the Ohio Supreme Court, on direct appeal, had decided the mental retardation issue under the same standard that court later adopted in Lott, and that the state court’s recognition of Bies’ mental state had been necessary to the death penalty judgment. When the Sixth Circuit denied the State’s petition for rehearing en banc, a concurring judge offered an alternative basis for decision. He opined that, under Sattazahn v. Pennsylvania, 537 U. S. 101 , jeopardy attaches once a capital defendant is “acquitted” based on findings establishing an entitlement to a life sentence; reasoning that the Ohio courts’ mental retardation findings entitled Bies to a life sentence, he concluded that the Double Jeopardy Clause barred any renewed inquiry into Bies’ mental state.
Held: The Double Jeopardy Clause does not bar the Ohio courts from conducting a full hearing on Bies’ mental capacity. Pp. 7–11.
