I’m not a proponent of the death penalty, at least under current conditions. I worry that our current state governments cannot be trusted to apply the death penalty fairly and evenhandedly. But I also find many anti-death penalty arguments unpersuasive. In particular, I’m surprised by the number of death penalty opponents who present empirical arguments as though they constituted a categorical or “principled” case against the death penalty.
For instance, many death penalty opponents emphasize its irrevocability: Once someone is dead, you can’t bring them back. Now, this is clearly true – but it’s also true of other penalties, though to a lesser extent. Suppose I’m sentenced to 50 years in prison. I serve 40 of them, and then new evidence comes to light that sets me free. Nonetheless, I can never get back those 40 years. They are forever lost to me. Or what if that evidence never comes to light? Then I lose 50 years that can never be returned. Or what if I die in prison, before the evidence appears? Again, I’ve lost years of my life that can never be refunded. (This case would be problematic even if the state attempted to monetarily compensate freed innocents for the lost years of their lives.) Finally, some people sentenced to years in prison will receive the rape penalty, which may involve the transmission of HIV – another kind of death sentence, also irrevocable.
Given that most penalties – certainly those recommended as alternatives to the death penalty – are to some extent irrevocable, the irrevocability argument against the death penalty boils down to a claim that the death penalty is somehow more severely irrevocable than other penalties. That, however, is an empirical claim whose validity depends on the magnitude of the death penalty’s deterrent effect.
Why? Because even if your only goal were to minimize lost years of life to innocent people, the death penalty could actually reduce the number of such years if the deterrent effect were large enough. Think of it this way: The death penalty, if effective, reduces the number of murders. Fewer murders means fewer murder trials. Fewer murder trials means fewer convictions. And fewer convictions means fewer convictions of innocent persons (assuming the institution of the death penalty is not accompanied by a weakening of the standards of evidence).
In short, an effective death penalty could reduce the number of innocents punished by the criminal justice system. Thus, there is a trade-off. On the one hand, the number of innocents convicted falls; on the other hand, some of the innocents still convicted receive a harsher punishment.
Consider some numbers. Suppose there are 1000 murders per year without the death penalty (with convicted persons receiving life sentences instead). Suppose imposing the death penalty, in some or all cases, will reduce the murder rate by 30%, to 700 per year. Suppose that 50% of cases result in a conviction, and suppose the wrongful conviction rate is 10%. Then without the death penalty, there will be 1000*50%*10% = 50 innocent persons convicted. With the death penalty, there will be 700*50%*10% = 35 innocent persons convicted. So instituting the death penalty saves 15 innocent people from conviction. On the other hand, hopefully some of the 50 innocents convicted without the death penalty will eventually be vindicated and set free. Suppose, very generously, that this happens 20% of the time, and (again generously) they are fully compensated for their lost years. This reduces the number of innocents irrevocably punished to 40 – still greater than the 35 under the death penalty. And note that we haven’t even considered the 300 prevented murders!
Now, the figures above are totally hypothetical, and I don’t claim they’re anywhere near correct. A smaller deterrent effect or a greater reversal rate could alter the outcome. (Changing the overall conviction rate or wrongful conviction rate would not alter the outcome, however, since those numbers apply both with and without the death penalty.) My point is that which penalty regime imposes the smallest burden, in terms of irrevocable convictions of innocent people, depends crucially on the empirical facts. An opponent of the death penalty who relies on the irrevocability argument should, therefore, be willing to reverse her position if presented with the right data. Yet the irrevocability argument is typically presented as though it were a knock-down point against the death penalty.