Deterrence and the Death Penalty (2012) / Chapter Skim
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6 Challenges to Identifying Deterrent Effects
6 Challenges to Identifying Deterrent Effects
Pages 101-124
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From page 101... ...
The second basic deficiency is failure to pose a credible model of the sanction risk perceptions of potential murderers and the behavioral response to such perceptions. In the absence of such a model, it is difficult, at best, to interpret data relating sanction regimes to homicide rates.
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From page 102... ...
Still another deficiency is inattention to potential feedbacks through which homicide rates, and crime rates more generally, may affect the specification and administration of a sanction regime while the regime simultaneously affects homicide rates. Recognition of potential feedbacks is relevant both to identify the direct effect of capital punishment on homicide rates and to predict the ultimate effect after feedbacks occur.
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From page 103... ...
And even if research on perceptions of the risk of capital punishment cannot resolve all major issues, some progress would be an important step forward. Even if these advances prove unsuccessful in providing useful information on the incremental deterrent effect of capital punishment in relation to a lengthy prison sentence, the committee believes that there are potentially major benefits from new data collection, theory, and methodology for study of the effect of noncapital sanctions on crimes not subject to the death penalty.
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From page 104... ...
Such a correlation would bias the estimated deterrent effect of capital punishment. None of the studies we reviewed sought to measure the availability and intensity of use of the noncapital sanction alternatives for the punishment of homicide.
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From page 105... ...
PERCEPTIONS OF SANCTION RISKS As emphasized in Chapter 3, it is not possible to interpret empirical evidence on the relationship of homicide rates to sanctions without understanding how potential murderers perceive sanction regimes.
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From page 106... ...
perceived by potential murderers. Panel studies typically suppose that people who are contemplating murder perceive sanctions risks as subjective probabilities of arrest, conviction, and execution.
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From page 107... ...
To make headway on whether and to what degree the death penalty affects the behavior of potential murderers, it is imperative to have knowledge about how their perceptions of execution risk are formed and then possibly revised on the basis of new information. RECOMMENDATION: The committee strongly recommends that a concerted effort be made to research the origins and nature of execu tion sanctions risk perceptions specifically and of noncapital sanctions risks more broadly.
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From page 108... ...
Thus, the first step and an important prerequisite for a program of research on sanction risk perceptions is to define the relevant population of potential murderers and, more generally, potential criminals. Such a definition will be required to devise cost-effective sampling strategies for interviewing people with nontrivial risks of committing crimes.
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From page 109... ...
The lessons learned from this exploratory research would inform the design of larger studies, the aim being to eventually develop a program of survey research that would regularly measure the perceptions of the sanction risk held by potential murderers and by potential criminals more generally. The committee is not confident that measurement of the sanctions risk perceptions of potential murderers can succeed in producing information useful to the study of deterrence, but one cannot be sure unless the effort is made.
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From page 110... ...
As discussed in Chapter 5, the time-series research has largely been devoted to the question of whether homicide rates change in the immediate aftermath of an execution. For the reasons detailed in that chapter, the committee concluded that existing studies were not informative about whether capital punishment affects homicide rates, in part because of the absence of any measure of perceptions.
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From page 111... ...
To better understand these issues, we highlight three related identification problems that complicate efforts to draw credible inferences on the effect of capital punishment on homicides. The first, referred to as a feedback effect, arises when homicide rates may directly affect the capital sanction regime.
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From page 112... ...
If variables that are jointly associated with the sanction regime and homicide rates are omitted from statistical models of the effect of capital punishment on homicide, then estimates of the deterrent effect will be biased. The panel research includes studies that recognize and attempt to address the inferential consequences of feedback effects and omitted variable problems.
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From page 113... ...
would be solved. What would remain, however, is the potential difficulty in isolating the deterrent effect of the death penalty by itself from the changes in the overall sanction regime that are influenced by the availability and use of the death penalty.
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From page 114... ...
Is a more reliable approach to identifying the deterrent effect of capital punishment possible? Part of the solution may be to develop a better understanding of the factors that affect sanction regimes, including possible feedbacks from homicide or other crime patterns.
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From page 115... ...
ADDRESSING MODEL UNCERTAINTY WITH WEAKER ASSUMPTIONS The persistent problems that researchers have had in providing meaningful answers about the deterrent effect of capital punishment is unsurprising once one recognizes that this body of empirical research rests on strong and unverified assumptions. Although, in practice, researchers often recognize and acknowledge that their assumptions may not hold, they are defended as necessary to provide meaningful answers and in order to make inferences.
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From page 116... ...
Although the resulting inferences may reflect a certain degree of ambiguity about the effects of capital punishment on homicides, those inferences will necessarily possess greater credibility. To explore the idea of addressing model uncertainty, the committee commissioned papers illustrating application of two complementary research paradigms -- the model averaging approach and the partial identification approach.
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From page 117... ...
In both papers, the researchers find that model uncertainty swamps the informational content about deterrent effects. That is, after accounting for the modeling uncertainty, the empirical evidence does not reveal whether capital punishment increases or decreases homicides.
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From page 118... ...
which there may be disagreement. Such disagreement should not obscure an essential strength of the model averaging approach: model averaging provides an approach for systematically exploring sensitivity over an explicitly defined model space.
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From page 119... ...
Under these weaker assumptions, deterrent effects may not be point identified, but they will be partially identified, with bounds rather than point estimates. Thus, the partial identification approach formalizes the inherent tradeoff between the strength of the maintained assumptions and the credibility of inferences (see Manski, 2003)
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From page 120... ...
Thus, under these weaker models, the average treatment effect of capital punishment is bounded, but the data do not identify whether the death penalty increases or decreases homicides. The committee does not endorse the specific findings of the recent studies applying the model averaging or partial identification approaches.
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From page 121... ...
. Model uncertainty and the deter rent effect of capital punishment.
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From page 122... ...
. Deterrent effect of capital punishment -- Question of life and death.
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From page 123... ...
. Bayesian model averaging for linear regression models.
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