In Zant, Warden v. Moore (1988), the U.S Supreme Court ruled on a case involving Jerome Bowden, who was convicted of murder and sentenced to death in Georgia. The defense argued that Bowden's intellectual disability should have precluded him from receiving the death penalty under Georgia law. However, at his trial, no evidence of this disability was presented nor did it appear in any subsequent appeals until after his execution had been scheduled. The Supreme Court held that because this claim had not been raised at an appropriate time or manner according to state procedural rules, it could not be considered as grounds for federal habeas corpus relief unless the defendant could show cause for failing to raise it earlier and actual prejudice resulting from its omission.

In the dissenting opinion for Zant, Warden v. Moore, Justice Marshall argued that Georgia's capital sentencing scheme was unconstitutional because it allowed a jury to impose death penalty based on an invalid aggravating circumstance. He believed this violated the Eighth and Fourteenth Amendments' requirement of heightened reliability in death penalty cases. The majority ruled that even if one of several aggravating circumstances is invalidated, as long as at least one valid reason remains, the sentence can stand. However, Marshall disagreed with this "harmless error" approach in capital punishment context due to its irreversible nature and potential for arbitrariness or biasness in decision-making process by juries who might be influenced by invalid factors while deciding life-or-death matters.