I hear ya on that one, Riana, BUT ...
some of these murders are committed in fairly gruesome ways ...
and NOT that the murderers are very much deserving of having the same amount of pain inflicted upon them, as they did upon their victims ...
BUT, someone would have to actually perform those acts of violence on them, which, being very much depraved, would necessarily inflict psychological harm upon the executioner.
In short, I wouldn't care about the harm to the condemned, but I would care about the harm to the executioner.
IMHO, it's better to make the execution as quick and as impersonal as possible and then let God sort it all out from there.