Penry v. Lynaugh - 492 U.S. 302, 109 S. Ct. 2934 (1989)

Rule:

Mental retardation has long been regarded as a factor that may diminish an individual's culpability for a criminal act. In its most severe forms, mental retardation may result in complete exculpation from criminal responsibility. The sentencing body must be allowed to consider mental retardation as a mitigating circumstance in making the individualized determination whether death is the appropriate punishment in a particular case.

Facts:

Defendant had the intelligence of a 9- or 10-year-old and he was unable to learn from his mistakes. In a Texas state court, even though the defendant presented evidence of his mental retardation and his background of childhood abuse, the jury found the accused competent to stand trial, and at the guilt phase of the trial, rejected the defendant’s insanity defense and found him guilty of capital murder. At the close of the penalty hearing, the jury was asked to respond to three special issues, none of which authorized the discretionary grant of mercy based upon the existence of mitigating circumstances. After the defendant’s unsuccessful direct appeals, he filed a habeas corpus petition in a Federal District Court and included claims that his death sentence violated the Eighth Amendment, because the trial court failed to instruct the jury on how to weigh mitigating factors in answering the special issues; and it was cruel and unusual punishment to execute a mentally retarded person. The District Court, however, denied relief, and, on appeal, the United States Court of Appeals for the Fifth Circuit, affirming, expressed the view that although there was some question whether the accused had been given the individualized sentencing that the Constitution required, prior Court of Appeals decisions required the Court of Appeals to reject the defendant’s claims in that respect; and it was not cruel and unusual punishment to execute a mentally retarded person such as the defendant. Defendant sought a writ of certiorari. 

Issue:

Under the circumstances, should the jury consider defendant’s mitigating evidence of mental retardation in its imposition of death sentence? 

Answer:

Yes.

Conclusion:

The Court held that in the absence of instructions informing the jury that it could consider and give effect to the defendant's mitigating evidence of mental retardation or background of childhood abuse, the imposition of a death sentence on the defendant’s under the Texas capital sentencing procedure violated the Eighth Amendment's prohibition against cruel and unusual punishments, because, under the circumstances, the jury was not provided with a vehicle for expressing its reasoned moral response to such mitigating evidence in rendering its sentencing decision. However, the Court held that defendant’s request that mental retardation be a bar to capital punishment would have been a new rule, and as a threshold matter, a new rule would not be applied or announced in cases on collateral review. The Court remanded the matter for further proceedings so that a jury could consider defendant's mitigating circumstances in determining whether to impose the death penalty.