well it will help to forestall the person being dead if exonerating evidence comes along, although anticipating the next question - yes, they can of course die

well it will help to forestall the person being dead if exonerating evidence comes along, although anticipating the next question - yes, they can of course die for other reasons in prison, but not having any stats to back it up I will just state my very strong suspicion that most people on death row who die in prison do so because the death penalty was applied.