I think the death penalty is used more as a deterent, or bargining tool then anything else.

If we are to trust courts with matters of our civil liberties, our rights and freedoms, overall our well fare, then I think it's not a far stretch to allow them to judge if a person should be put to death.

At the moment, I'm still on the fence about the death penalty, so this is just the first thing that came into my mind when I read your question.