To those of you saying that the death penalty is OK when you're sure they did it, and not when there's any doubt:
The trouble with having the death penalty when you're sure they did it, and just putting them in jail for life if you're not sure, is that then it's not the severity of the crime that determines the punishment, it's how sure you are. And after all, if you can say, "We're not 100% sure you did it, just 79% sure, so we'll put you in jail for life instead of executing you," then perhaps you're not sure enough to lock them up for life either. And someone caught red-handed for a lesser crime might be executed, while someone prosecuted for a greater crime is locked up.