It seems even the death penalty is not effective as a deterrent (except for detering future acts by the subject of said penalty).
I don't think the people who commit most serious criminal acts can think very far ahead, like far ahead enough to when they might be caught. If you aren't going to get caught, then why worry about the penalty?
It has been said that 3 Strikes in California has resulted in more shoot-outs with police by those facing a third conviction, but I have seen no reliable statistics on that.