A fellow blogger had a great entry on capital punishment, something I personally have yet to delve into deeply from a policy perspective. He laid out rather clearly the inherent difficulties in measuring whether the death penalty has an effect on crime, homicides to be exact.
1) What are you comparing it to? Better stated, what would the alternative punishment have been to those offenders? Very few of the existing studies detail this.
2) You need to make assumptions as to how potential murderers perceive the penalty. Are they aware it exists, under what circumstance, what are their chances?
3) Cause and effect – arguably impossible to find two significantly large identical populations with which to create control and treatment groups. This isn’t like a Coke and Pepsi challenge with high-school kids.
Up to this point I had heard these arguments, but what got me was his conclusion, which I am still grappling with. If we, as in the world (because each and every country grapples with this issue, some more fervently than others), can agree on the uncertainty of whether or how much capital punishment deters future murderers, and we need to make a decision whether to execute certain murderers or not, consider 4 possibilities:
1) Country X decides to execute only some murderers, and this does result in deterring other murders. PLUS (with a caveat) AS THEY MIGHT HAVE BEEN INNOCENT
2) Country X decides to execute only some murderers, and this does not result in deterring other murders. POTENTIAL LOSS, AS THEY MIGHT HAVE BEEN INNOCENT
3) Country X decides not to execute any murderers and it doesn’t matter as it wouldn’t have deterred anyone anyways. WASH
4) Country X decides not to execute any murderers but it would have saved lives had they done so. POTENTIAL GAIN
So, in the end, those folks who argue against capital punishment clearly have a case.
BUT … as the possibilities above have also shown, capital punishment could deter future murders, so if we are not sure, we should also take into account that executing the worst of the worst (i.e., those we know beyond a shadow of a doubt are guilty) might actually save lives.
Note: The moral argument obviously does not factor in here and I personally am undecided on the issue.