whether capital punishment is a legally permissible sanction. Other studies have examined whether homicide rates are associated with moratoriums on executions ordered by governors or courts. There is also a distinct set of studies that have examined whether the frequency of and publicity given to actual executions are related to homicide rates. One part of this research has examined whether execution events seem to affect homicide rates; another part has examined whether homicide rates are associated with various measures of the probability of being executed for homicide.

Our overview of key challenges to making an empirical assessment of the effect of capital punishment on homicide rates is necessarily selective. There is an enormous research literature on the mechanisms by which legal sanctions, of which the death penalty is but one, might affect crime rates. There is also a very large research literature on the econometric and statistical methods used to estimate the effect of the death penalty on homicide rates. We focus on those issues that are particularly important to the reviews and critiques of the panel and time-series literatures in Chapters 4 and 5, respectively. These issues include data limitations, factors beyond the death penalty that contribute to large differences in murder rates across place and over time, possible feedback effects by which homicide rates might affect the administration of the death penalty, how sanction risks are perceived, and the concept of a sanction regime.

There is also a literature that examines the argument that executions may actually exacerbate homicide rates through a brutalization effect. This argument has been studied using the same statistical tools as deterrence, although the mechanism being studied is different. With one exception, all of these are time-series studies, and we review them in Chapter 5.

CONCEPTS OF DETERRENCE

Going back at least 200 years to the legal philosophers Cesare Beccaria in Italy and Jeremy Bentham in England, scholars have speculated on the deterrent effect of official sanctions. At its most basic level, deterrence is typically understood as operating within a theory of choice in which would-be offenders balance the benefits and costs of crime. In the context of murder, the benefits may be tangible, such as pecuniary gain or silencing a potential witness, but they may also involve intangibles, such as defending one’s honor, expressing outrage, demonstrating dominance, or simply seeking thrills. The potential costs of crime are comparably varied. Crime can entail personal risk if the victim resists (see, e.g., Cook, 1986). It may also invoke pangs of conscience or shame (see, e.g., Braithwaite, 1989).

In this report we are mainly concerned with the response of would-be offenders to the sanction costs that may result from the commission of murder. Such sanction costs will typically include lengthy imprisonment. Properly



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