Earlier quoted context omitted.
So, question- if you actively support putting people behind bars with the intent of seeing them die there, why not just kill them right away? If the intent is for them to not cause any harm to society, then that'll get the job done while saving money for society and making them suffer for a shorter period of time. Unless the goal is to make them suffer for their entire life as punishment; in which case, why not just…
It's very difficult to release an executed man if new evidence shows he's innocent after all.
I don't find the death penalty especially sui generis for that reason.