The U.S. Supreme Court case John Paul Penry v. Gary L. Johnson, Director, Texas Department of Criminal Justice, Institutional Division (2000) revolved around the issue of whether a death sentence can be imposed on an intellectually disabled individual and if such punishment violates the Eighth Amendment's prohibition against cruel and unusual punishments. The defendant in this case was John Paul Penry who had been convicted for rape and murder in Texas but was found to have significant intellectual disabilities with an IQ between 50-63 which is equivalent to a mental age of six-and-a-half-year-old child. In its decision, the court held that executing individuals with intellectual disabilities did not violate the Eighth Amendment per se; however, it emphasized that juries must be able to consider and give effect to mitigating evidence about a defendant’s disability when deciding upon capital punishment.

In the dissenting opinion for Penry v. Johnson, Justice Scalia argued that the majority had overstepped its bounds by essentially rewriting Texas's capital sentencing statute. He contended that there was no constitutional requirement to instruct juries about mitigating evidence in a specific way and criticized the majority for creating such a rule based on their own policy preferences rather than established law. Furthermore, he believed that Penry had been given ample opportunity to present his mental impairment as a mitigating factor during his trial and thus saw no reason why this case should be treated differently from others where similar issues were raised but did not lead to reversal of death sentences. In essence, Scalia felt that the Court was improperly intervening in state criminal justice systems and undermining their ability to administer justice effectively.