The Court examined constitutionally required jury instructions concerning the meaning of life imprisonment, the implications of the insanity defense, and the specifics of aggravating and mitigating factors that may affect a defendant's sentence. The Court also overturned a death sentence, holding that when a defendant's future dangerousness is at issue in a sentencing proceeding and the defendant is ineligible for parole under State law, the sentencing jury just be informed of the ineligibility if the defendant's right of due process is to be protected.