In the case of Robert L. Ayers, Jr., Acting Warden v. Fernando Belmontes in 2006, the U.S Supreme Court ruled on whether a jury instruction during sentencing was constitutionally adequate in allowing consideration of mitigating evidence presented by defendant Fernando Belmontes. The court held that it was indeed sufficient and did not violate his Eighth Amendment rights against cruel and unusual punishment as argued by Belmontes' defense team. The decision overturned an earlier ruling from the Ninth Circuit Court of Appeals which had sided with Belmontes, stating that jurors may have been confused or restricted by instructions given at trial regarding how to consider his background when deciding on a sentence for murder conviction.

In the dissenting opinion for Ayers v. Belmontes, Justice Stevens argued that the jury was not adequately instructed to consider all mitigating evidence in sentencing Fernando Belmontes to death. He contended that the trial court's instructions were misleading and could have led jurors to believe they should disregard certain aspects of Belmontes' background when considering his sentence. The majority held that these instructions did not violate the Eighth Amendment, but Stevens disagreed, arguing they undermined a fundamental principle of capital punishment jurisprudence: juries must be allowed to give full consideration and effect to mitigating circumstances. Furthermore, he believed there was reasonable likelihood this misinstruction affected the jury’s sentencing decision given substantial evidence about Belmontes’ potential for rehabilitation presented during penalty phase – which might have been disregarded due to faulty instruction.