Well, "individual recidivism" for sure...
In any event, I have always believed (and I'm sure Glen can verify from our previous "discussions"), that Capital Punishment really shouldn't serve that purpose, or any other purpose, except one... to be that "necessary and sufficient measure of justice..." for the committed crime and the circumstances surrounding it. It's all about the justice.... at least for me. It's all about the pursuit of justice for the victims of those crimes... especially those that are no longer with us to fight on their own. We fight for them, and their surviving families. I don't care about recidivism, deterrence or any of those other things. If they happen, then so much the better, but the only thing that matters to me is the service of justice. Is the justice system perfect? Absolutely not. And we need to do much better at ensuring that those who deserve Capital Punishment actually do. Does it cost a lot of $$$? Absolutely. But should cost be an excuse to deny justice to victims (and survivors) that deserve it? I think not.
Thus, again, the one and only one question to be asked and answered is, "Are there crimes and circumstances for which the 'forfeiture of life' is that necessary and sufficient measure of justice?"
My answer: Yes.