Did anyone say the meaning of self-defense changed based on one's location? No. No one has said that. That's you making stuff up. Murders can and do kill more than just one person. There are serial murders, and that's primarily who we are talking about here, and they don't stop killing just because they are locked up. They are a threat to fellow prisoners and guards and they do escape. It was just a few weeks ago 2 murders escaped from a high security prison. And as much as you dislike it, deterrence is a collective self-defense. We do not know with specificity which lives will be saved. But we do know lives will be saved, it's in the numbers. That doesn't make sense. People commonly get killed in prison with or without the death penalty. Fellow criminals kill each other, and? They create and execute their own death penalties on fellow inmates and prison guards. Without the death penalty, there is little disincentive to murdering a fellow inmate or guard. Well that is your belief, it doesn't make it true or reasonable. Are you saying Ted Bundy wasn't guilty? There are cases which are particularly heinous and guilt is certain and for those cases the death penalty is an effective and reasonable remedy. We are not talking about cases where guilt is not overwhelming. In the statistics offered and discussed in this thread, error rates have been estimated to be between .5% and 4%. That is the science and those cases occurred before DNA became available to criminal investigators.