There's a post today about a 78 year-old murderer that served twenty years for killing wife #1 and wife #2.
Guess what? He killed wife #3, and accidentally himself, when he tried to use arson to cover the killings (I think he killed another person)
There was one last week. Convicted murderer gets released, only to kill again.
Bingo! Can the opponents of capital punishment point to a single case, even one, where it was proven that a convict was innocent after he was executed by mistake? Compare that to the veritable rivers of blood shed by people who were released from prison.