Though I agree that in most cases death penalty should not be used, in some very specific but not rare cases - like mass shootings with dozens dead - where you have a lot of video and DNA evidence and dozens of witnesses - I just can't find a single argument against it. If I find any - I would gladly change my mind.
Then let me offer you this question to ponder: What benefit is there to adding another tally to the body count from a mass shooting, once the perpetrator has been taken into custody?
Executing someone doesn't reduce the number of unnecessarily lost lives, it only increases it.
Someone who is assaulted or robbed might also benefit from the sense of closure they would receive knowing that the perpetrator had died. Similarly someone who found their partner cheating on them with a rival might find it easier to move on from that if their rival was then killed.
In general I don't think that society is best served by legitimising and implementing the irrational desires we have for killing people who have emotionally hurt us.
I think it would instead make sense to try to improve the support given to people who have suffered from crimes. If this means years of expensive therapy, paid for by the near-slavery of the perpetrator carrying out their life sentence, then we could have an outcome that is slightly more humane.
I think spending the rest of your life in solitary in a supermax prison sounds like a fate much worse than death. I'd rather see that happen to a terrorist than the death penalty.
