So say Cass Sunstein and Adrian Vermeule in their 2005 Stanford Law Review article, as quoted in today's NY Times on the new consensus about the deterrent effect of the death penalty.
I am not comfortable with instrumental arguments in favor of the death penalty, and while several researchers cited say they are against the death penalty but..., others do seem to be making exactly such an argument (eg Sustein and Vermeule). There are a LOT of things we as a society could do to deter crime (public shaming, putting people in stocks, flogging) that we do not do that are far less extreme than execution. Giving a government the power to kill its own citizens is not something I favor no matter how lovely one particular side effect may be.
ps. as an example of why we economists are not really welcome in polite circles, consider Justin Wolfers' answer to the question of whether or not it is conceptually possible to determine if the death penalty has a deterrent effect (Wolfers is skeptical of the existing studies due to limitations of the data):
Professor Wolfers said the answer to the question of whether the death penalty deterred was “not unknowable in the abstract,” given enough data.
“If I was allowed 1,000 executions and 1,000 exonerations, and I was allowed to do it in a random, focused way,” he said, “I could probably give you an answer.”ummm, ok Justin, thanks. We'll have to get back to you on that. In the meantime, why not write it up as an NSF proposal?