May be imposed only under state statutory scheme that provides:
- clear objective standard
- specific and detailed guidance
- opportunity for rational review of process.
- trier of fact must find at liase one aggravating circumstance to warrant death penalty. Automatically excessive in felony-murder cases and where there was no intent to kill or intent to use lethal force.
- no death penalty for insane, mental retardation, those younger than 18 at time of crime.