I believe that is it not possible to be 100% sure. Where there is a small chance it is not the right judgment; people should not be killed. Life in prison. No parole, no benefits. Death is too much & what gives us the justification to do it unless we are 100%? There is no going back after death right? There are too many unsafe convictions & for this reason, people shouldn't be killed.
FYI I believe in death penalty for paedophiles, rapists, murderers & other twisted acts of unprovoked or sadistic violence. If we are sure of course