imo a civilized society doesn't commit murder.
Executions are in my view engaging in the very act you're punishing the inmate for. You're doing it also on the taxpayers dime. There's also the problems of cost being more than life imprisonment, being poorly and painfully administered, and having innocent people in line to be executed. Since most people don't get off death row my guess is from time to time we kill an innocent person.
No one seems to care though. Everyone just has an emotional sense of relief when someone dies for something that is unfortunate, sad and irreversible.