Death Penalty as Deterrent: Arguments For Capital Punishment

Introduction: The Deterrence Question

If it is difficult — perhaps impossible — to prove statistically, and just as hard to disprove, that the death penalty deters more from capital crimes than available alternative punishments such as life imprisonment, why do so many people believe so firmly that the death penalty is a more effective deterrent?

Some are persuaded by irrelevant arguments. They insist that the death penalty at least ensures that the person who suffered it will not commit other crimes. True — yet this confuses incapacitation with one particular way of achieving it: death. Death is the surest way to bring about total incapacitation, and it is irrevocable. But does incapacitation need to be that total? And is irrevocability necessarily an advantage? Obviously, it makes correcting mistakes and rehabilitation impossible. What, then, is the advantage of execution over alternative ways of achieving the desired incapacitation? More importantly, the argument for incapacitation confuses the elimination of one murderer — or of any number of murderers — with a reduction in the homicide rate. The elimination of any specific number of actual or even potential murderers will not affect the homicide rate, except through deterrence. There are enough potential murderers to replace all those incapacitated. Deterrence may prevent the potential from becoming actual murderers, but incapacitation of some or all actual murderers is not likely to have much effect by itself. The question remains: does capital punishment deter more than life imprisonment?

Science, logic, or statistics have often been unable to prove what common sense tells us to be true. The Greek philosopher Zeno, roughly 2,000 years ago, found that he could not demonstrate that motion is possible; indeed, his famous paradoxes appear to show that motion is impossible. Though nobody believed them to be true, nobody succeeded in exposing the fallacy of those paradoxes until the rise of mathematical logic less than a hundred years ago. Yet the world did not stand still in the interim. Nobody argued that motion should stop because it had not been shown to be logically possible. There is no more reason to abolish the death penalty than there was to abolish motion simply because the death penalty has not been — and perhaps cannot be — shown statistically to be a deterrent over and above other penalties. There are, in fact, two quite satisfactory, if non-statistical, indications of the marginal deterrent effect of the death penalty.

Once a punishment exceeds, say, ten years in prison (net of parole), there may be little additional deterrence gained by threatening additional years. We know very little about diminishing returns in the area of criminal penalties. It still seems likely, however, that the threat of life in prison deters more than any shorter term of imprisonment, and the threat of death may deter still more. It is a mistake to regard the death penalty as though it were merely another point on the same continuum of penalties. Death differs significantly, in kind, from any other punishment. Life in prison is still life, however unpleasant. The death penalty, by contrast, does not merely threaten to make life unpleasant — it threatens to take life altogether. This difference is perceived by those most directly affected. When prisoners under sentence of death are given the choice between life in prison and execution, 99% prefer life in prison. Through appeals, pleas for commutation, and every other available means, they demonstrate that they prefer life in prison to execution.

From this unquestioned fact, a reasonable conclusion can be drawn in favor of the superior deterrent effect of the death penalty. Those who have the choice in practice — those whose choice has actual and immediate effects on their own survival — fear death more than they fear life in prison or any other available penalty. If they do, it follows that the threat of the death penalty, all other things being equal, is likely to deter more than the threat of life in prison. One is most deterred by what one fears most.

Suppose one is not fully convinced of the superior deterrent effect of the death penalty. Even if one is genuinely uncertain whether the death penalty adds to deterrence, one should still favor it from a purely deterrent viewpoint. If we are uncertain, we must choose between two alternatives: (1) trading the certain death, by execution, of a convicted murderer for the probable survival of an indefinite number of future murder victims — whose survival becomes more likely if the convicted murderer's execution deters prospective murderers — or (2) trading the certain survival of the convicted murderer for the probable loss of the lives of future murder victims, who are more likely to be killed because the convicted murderer's non-execution failed to deter prospective murderers who might have been deterred by an execution.

To restate the matter: if we were entirely ignorant about the marginal deterrent effects of execution, we would have to choose between the certainty of the convicted murderer's death by execution and the likelihood of the survival of future victims on the one hand, and on the other his certain survival and the likelihood of the deaths of new victims. The preferable choice is to execute a person convicted of murdering others rather than to put the lives of innocents at risk.

Those who insist that the death penalty has not been demonstrated to be more deterrent than other penalties may not genuinely believe that it is not, or that deterrence even matters. The deterrent effect of the death penalty — or its absence — does not appear to be what actually drives abolitionist opposition. Rather, the lack of statistical demonstration of a marginal deterrent effect is used to rationalize opposition that has other, non-rational sources. In fact, most abolitionists are not entirely serious about the relevance of their own argument from insufficient deterrence.