So when it comes to the kind of people who become criminals—which is to say, people who are pretty bad at rationally weighing the future consequences of their actions—the death penalty is exactly the wrong deterrent. It makes punishment worse, but also, even less likely.
Not convinced? Remember that drug dealers are already living under the threat of the death penalty—from each other. With no legal recourse for contract enforcement, drug cartels often rely on violence to protect turf, punish people who cheat them, and occasionally, to open up a spot for personal advancement within their organization. If the threat of getting shot by a fellow street pharmacist doesn’t deter dealers, why would they be scared by an even more unlikely threat of getting caught, put on trial and eventually sentenced to lethal injection?
If we really want to deter them, we need to increase the odds of something bad happening to them right now. That means more law-enforcement officers on the streets; it also means more effective punishment models, such as the “swift, certain and fair” framework that has been advanced by Kleiman and others.