Capital punishment revisited

In my previous posting on the death penalty I said I was against it in part because I was unconvinced as to its effectiveness. But according to this law professor the death penalty can be effective in preventing murders as long as it is used with regular frequency.

This is a tough one for me. I really want to be for the death penalty -- I think murderers should get their just desserts and I'm all for deterring crime. But on the other hand the thought of innocent people being executed turns my stomach. Thoughts?