Well, maybe. Maybe not.
Let's leave behind the deterrence studies and the statistics for a moment. As Mark Twain said, "There are three kinds of lies: lies, damned lies and statistics."
The truth of the matter is, every study that has been done on deterrence gets twisted and contorted into support for the death penalty or opposition to the death penalty when in point of fact the statistics don't seem to show anything, one way or another.
Let's think about this from a common sense perspective. I recently was pleasantly surprised to see this commentary filter in to my email box from our Indiana affiliate:
The next time there's an execution in your state, ask 10 average people you know (who aren't abolitionists or death penalty promoters) the name of the person executed and what their crime was. In my experience, even educated, supposedly "engaged" people can't answer correctly. If folks like that don't know the reasons why someone was executed, then how in the world can the death penalty deter a drug addict robbing the local 7-11 for money for more drugs? People who commit murder simply do not make the fine calculations that death penalty supporters claim they do.