>Actually, I'm pretty sure the statistics show that the death penalty is not a deterrent.

Indeed, and the studies are statistically well done, AFAIK. However, I tend to take those studies with a large grain of salt, for a simple reason:

There has been little finality with CP in the modern US - in most states it has taken 10-12 years to consummate the entire process, and often it never does occur. That's not going to provide much deterrent weight, if it takes that long and/or is of varying certainty. Deterrence requires more immediacy of punishment, IMO.

Not that I'm saying either that we should "string suspects up on the spot," either, but if you want a good measure of deterrence alone I think you would need to factor the delay in.

I.e., in some countries where you're convicted and your life is taken (or your hand cut off, etc.) almost immediately after a crime is committed, there is probably a very serious punishment/deterrent factor. Especially those countries that use public punishments...(okay, I know we're getting a little gross now, but you get the idea).