What is the legal test used to determine whether a defendant should receive the death penalty?

Under the Eighth Amendment, there are "two different aspects of the capital decisionmaking process: the eligibility decision and the selection decision." Tuilaepa v. California, 512 U.S. 967, 971 (1994). "To render a defendant eligible for the death penalty in a homicide case, . . . the trier of fact must convict the defendant of murder and find an 'aggravating circumstance' (or its equivalent) at either the guilt or penalty phase." Id. at 971-72.

The selection decision "determines whether a defendant eligible for the death penalty should in fact receive that sentence." Id. at 972. This requires an individualized determination, considering "relevant mitigating evidence of the character and record of the defendant and the circumstances of the crime." Id. While "statutory aggravating circumstances play a constitutionally necessary function" by "circumscrib[ing] the class of persons eligible for the death penalty . . . . [t]he Constitution does not require the jury to ignore other possible aggravating factors in the process of selecting, from among that class, those defendants who will actually be sentenced to death." Zant v. Stephens, 462 U.S. 862, 878 (1983). Thus, after the jury finds at least one statutory aggravating circumstance, rendering the defendant eligible for the death penalty, it must still weigh other aggravating and mitigating circumstances, including non-statutory aggravating factors, to determine whether the death penalty should actually be applied in a particular case.