I’d just like to add an argument against the death penalty. The common argument is that we sometimes get it wrong so we can’t have it because you can’t reverse the sentence, and that is a strong enough argument. However, if one day we have a justice system that can be 100.000% certain of guilt (or society at large is persuaded of this, even if it isn’t true…) then I still don’t believe we should have the death penalty, because it’s not possible to be 100% certain that there is no chance of rehabilitation. I’m someone who has had a family member horrifically and senselessly murdered, and I still believe revenge achieves exactly nothing. It just adds bodies to the pile and increases suffering. It won’t bring back your loved ones, or, crucially, reduce your suffering one iota to see the guilty suffer or die.
The question really is: why the hell would any civilised society, whose citizens believe themselves to have mastered their animalistic nature, want the death penalty?