The number of credible (but not proven) claims of innocent people being executed is about four since the death penalty was reinstated in about 1977. Balanced against that there are probably 30-50 innocent people killed each year by killers released from prison who kill again.
Vengence probably enters into the judgement much too often.
Vengeance may be desired by the victim’s family but in fact justice requires that the state impose a penalty commensurate with the severity of the crime.
I doubt it defers acts of passion.
It might not deter acts of passion but it seems undeniable that at least some killers would be deterred. How many innocent people have to be saved to make it a useful deterrent?
Repetence and redemtion are always possible.
As Samuel Johnson said: “Knowing you are going to die in a fortnight concentrates the mind wonderfully.” I think the argument that someone is likely to repent knowing he will be executed is at least as strong as expecting that he will repent from spending the rest of his days among criminals.
It can be Cruel and Unusual as it has been carried out.
I have a hard time with this argument. Most convicts are executed via lethal injection and there is nothing either cruel or unusual about that procedure.