So far what I read about the death penalty is the all too familiar hand wringing over cost and the classic misdirection of deterrence. Costs grow due to the lengthy appeals process. That can be changed. Discussion of deterrence has no value known to me.
I think I know the ultimate issue. Our surgeons remove cancerous tumors, because cancer spreads. All those who linger on death row benefit few but may infect all the other prisoners, the guards and anyone else they contact.