"According to roughly a dozen recent studies, executions save lives. For each inmate put to death, the studies say, 3 to 18 murders are prevented."
I've heard it stated as fact by so many lawyer-debaters that the death penalty doesn't work as a deterrent I'd assumed that was actually what the evidence showed. Instead it appears to be just a lawyers' urban myth.
I'm increasingly of the opinion that lawyers just don't like the idea of deterrence. It doesn't fit with the highly individualistic understanding of justice that their profession encourages them to think in terms of. Their job is to deal with cases in isolation. The importance of the broader impacts of sentencing to create a deterrent just isn't apparent when you're looking through that prism. Given that they're a group given massive power and unnaccountable to the world around them such a systematic cognitive bias among the legal community is pretty bloody important.