From what I've read, the death penalty isn't much of a deterrent to crime (vs life without). Maybe that's wrong, dunno. I've also read it costs more to execute than keep for 40+ years, which sounds rather odd. Maybe that's wrong.
Carrying it out remains pretty rare. One usually makes the news because of that, along with the usual vigils and protests etc.
I have a philosophical objections to allowing the State to execute an individual, but that doesn't mean I'm against it in practical terms. But, if practically, it really is not a deterrent and not cheaper, I'm against it.
Most heinous crimes are state crimes, like the usual murder cases.