There are certain pieces of "conventional wisdom" that I’m quite skeptical of. One of them is "The death penalty doesn’t really deter murders." Really? How do we know this? Whether one supports or opposes capital punishment, this claim is at least counterintuitive.
It would seem that executing a murderer would at least prevent him from committing repeat offenses and deter those murders–whether or not it scares off potential murderers from killing others. Further, isn’t the whole idea of having penalties attached to laws generally regarded as providing a deterrent? Why should this penalty be any different? Could the "it doesn’t save lives" argument be just wishful thinking?
I can imagine arguments that having the death penalty fosters a culture of death such that it actually leads to more murders. Maybe. Weird things like that happen. But where’s the data?
That’s why it’s nice that God created economists. They can be a big help in testing received bits of conventional wisdom and seeing if they hold up or if they’re just wishful or prima facie thinking.
The Sydney Morning Herald recently carried an op/ed piece touching on this that was startling:
NEVER have those of us who oppose the death penalty felt more convinced that we are right. And never has there been a series of more impressive-sounding arguments to suggest that we are wrong.
For most of the past century we have been secure in the belief that executing murderers does little to stop murder. That’s what the psychologists and the criminologists have told us.
But now economists have entered the debate. And they have brought to the task a dazzling range of highly sophisticated techniques originally developed to answer more prosaic questions, such as whether tax breaks encourage saving.
More often than not the economists find that executions do save lives.
As they starkly report their central finding: each execution results in an average of 18 fewer murders. Or, to present the finding in an even more unsettling way: any state that refuses to impose the death penalty for murder is condemning 18 or so innocent people to death.
Now, I know that claims of this nature are controversial and subject to testing and revision and reversal themselves, but it’s nice to have additional research being done. That’s how science–including criminology–moves forward.
READ THE SUNSTEIN-VERMUELE PAPER. (WARNING! Evil file format [.pdf]!)
DISCUSS.

