There’s a defense of the death penalty I’ve not seen mentioned, though I’m sure someone has addressed it somewhere. To start with the punch line, it seems to me the existence and imposition of the death penalty is a condition of the legitimacy of the state. What, after all, was the reason for the original social contract? Not the theoretical contracts that Hobbes, Locke, and Rousseau discussed, but the actual ones all over the world where family and clan groups at different points in history first submitted themselves to the state? It was to avenge murderers in a targeted, orderly, proportional, rule-based fashion, thus avoiding the disorder of private justice. Before that, and still in places with weak or non-existent states, families or clans would get justice on their own, so that when one of theirs was killed by a neighboring clan, they’d get the boys together and kill one of theirs. The problem with this, of course, is that it leads to endless cycles of vendetta or feuds, and doesn’t even necessarily result in the right person being punished. So people surrendered the right to avenge their kinsmen’s deaths in exchange for a promise by the state to avenge the deaths for them. As Jason said, when a someone’s loved one is murdered, it’s natural (and always will be, given the permanence of human nature) to insist that the murderer pays for his crime with his life. When the state, as a matter of policy, refuses under any circumstances to execute murderers, it welshes on the deal that brought the state into existence in the first place and undermines its legitmacy.