The U.S. Supreme Court case Lonnie Weeks, Jr. v. Ronald J. Angelone in 1999 revolved around the issue of jury instructions during capital sentencing proceedings and whether a judge's failure to clarify these instructions violated a defendant's constitutional rights under the Eighth Amendment (prohibition against cruel and unusual punishment) or Fourteenth Amendment (due process). The petitioner, Lonnie Weeks Jr., was convicted for murder in Virginia state court and sentenced to death by a jury that had been instructed they could consider mitigating evidence but were not explicitly told they could give it any weight they deemed appropriate when deciding on life imprisonment versus capital punishment. On appeal, Weeks argued this lack of clarification led jurors to believe their ability to weigh such evidence was limited, thus violating his constitutional rights. However, the Supreme Court ruled 5-4 against him stating that while juries should be properly informed about their role in considering mitigating factors during sentencing deliberations; there is no requirement for specific language or explicit instruction as long as jurors are aware of their responsibility overall - which according to them was satisfied here through other aspects of trial procedure.

In the dissenting opinion for Lonnie Weeks, Jr. v. Ronald J. Angelone, Justice Stevens argued that Virginia's capital sentencing scheme was unconstitutional because it failed to provide clear instructions on how jurors should weigh mitigating factors against aggravating ones when deciding whether to impose a death sentence. He believed this lack of guidance could lead juries to arbitrarily and inconsistently apply the death penalty, violating defendants' Eighth Amendment rights against cruel and unusual punishment. Furthermore, he criticized the majority for deferring too much to state courts in interpreting federal constitutional law rather than conducting an independent review of the case at hand.