The money-quote:

My view is that we shouldn’t execute people. We shouldn’t execute mass murderers. We shouldn’t execute cop killers. We shouldn’t execute child rapists. We shouldn’t execute terrorists. We should be seeking, so far as possible, to minimize the level of officially sanctioned violence and killing in order to promote a healthier, less bloodthirsty public culture. Executing murders is clearly not in any sense a necessary element of an effective crime control regime, so we should do without it.