Justice Kennedy, writing for the majority, warned about broader problems with the capital punishment. "When the law punishes by death, it risks its own sudden descent into brutality, transgressing the constitutional commitment to decency and restraint." He took into account the many dangers of the death penalty and concluded it should be restricted to homicides (Death Penalty Information Center, 2008).
The main question regarding the research for or against capital punishment as a deterrent is whether to continue the death penalty because the findings are inconsistent or to stop it for the same reason. Researchers Radelet and Borg (2000), in fact, say that the findings impact how Americans perceive the death penalty. They showed how the conclusions of the research over the past several decades have influenced the debate pro-or con capital punishment. Their literature review in relationship to historical events "suggests changes in the nature of death penalty debates are a direct consequence of social scientists' close and careful examination of the various dimensions of these arguments" (p; 44). He is hopeful that the more studies that show no connection will encourage people to no longer support the death penalty.
The fact is that there are no "facts" on which someone can actually rely to make a decision once for all regarding this issue. For the past three decades, study after study has had different variables, different methodology and different conclusions. Depending on a person's inclination about the death penalty, there will be research that supports it. It comes down to personal judgment on how to proceed. As a review conducted for the United Nations in 2002 of literature concluded: ". . .it is not prudent to accept the hypothesis that capital punishment deters murder to a marginally greater extent than does the threat and application of the supposedly lesser punishment of life imprisonment" (Hood, 2002, p. 230).
In 2005, Jeffrey Fagan of the Columbia Law School gave testimony to the State of New York Hearings on the Future of Capital Punishment in the State of New York stipulating that a close reading of the deterrence studies shows very clearly their failure to empirically prove capital punishment as a deterrent. His reasons included: 1) The studies lump all forms of murder together, noting that all can be equally deterred. However it is only logical that some types of murder, such as crimes of passion may be poor candidates for deterrence; 2) The research finds erratic and contradictory results, and some conclude that there is no deterrent effect. Capital punishment cannot tolerate these inconsistencies in one of its bedrock theoretical premises. Further, such inconsistencies are the antithesis to the robustness in research design that is mandatory for social scientists and economists
When the hypothesized deterrent effects of execution are so unstable over time, it is necessary to reject a deterrence hypothesis; and 3) These studies fail to deal with autoregression, or the tendency of trends in longitudinal data to be greatly influenced by the trends in preceding years. In other words, that what says the most about what the murder rate will be next year is what is was last year. It is unlikely that effects of very rare events such as executions can influence trends that are so greatly influenced by their own history.
Fagan continues: 4) There are few statistical controls for the overall performance of the criminal justice system, particularly clearance rates for violent crimes. It is hard to analyze the deterrent effects of execution without first knowing the homicide clearance rate. These essential yet omitted variables are potential sources not only of errors in these
analyses, but they produce misleading results; 5) The studies do not have a way of dealing with the significant missing data in important states such as Florida. The FBI's data for Florida is missing in the national archives normally used for research for four years in the 1980s and another four years in the 1990s; 6) The research does not do any .
direct tests of deterrence. They do not show that murderers have awareness of the executions in their own or any other state and thus decide forego homicide and use less lethal forms of violence; 7) The studies do not consider the deterrent effects of Life Without Parole sentences, which have the same incapacitative effect as does execution.
There are many death row inmates who did not fight their execution, because life in prison was worse than the death penalty; and 8) The research does not provide information on alternate causes of ups and downs in the murder rate. For instance, nearly all of the rise and fall in American homicides since 1985 was in gun homicides. Yet none of the studies consider the trend of decline in non-gun homicides since the early 1970s, gun availability, or the tremendous influence of the crack epidemic in the cities during the 1980s and early 1990s and its complex interaction with gun violence.
Weisberg (2005) addressed the idiosyncrasies the research on the death penalty. He explained that the social sciences have long played a role in analyzing the efficiency and fairness of the death penalty. The Supreme Court in its landmark cases in the 1970s
cited scientific studies concerning the deterrent effect of capital punishment, most notably Ehrlich's study, which used multivariate regression analysis and alleged to show a significant marginal deterrent effect over life imprisonment. However, his work was soon roundly criticized for methodological flaws. Decades later, a whole new series of new econometric studies emerged that used panel data techniques. These report striking findings of marginal deterrence, even up to 18 lives saved per execution. However, the continuous cycle of debate goes on, as these most recent studies are critiques for omitting key potential variables and due to the potential of distortion of figures because of the one anomalously high-executing state of Texas. Meanwhile, other researchers, relying mainly on survey questionnaires, are taking a fresh look at the human dynamics of death penalty trials, particularly the attitudes and personal background factors that influence capital jurors.
In 2005, John J. Donohue of Yale Law School and Justin Wolfers of the University of Pennsylvania, wrote in the Stanford Law Review: "Our estimates suggest not just 'reasonable doubt' about whether there is any deterrent effect of the death penalty, but profound uncertainty." This uncertainty comes from the fact that some studies have "conclusively" found capital punishment deters crime, some found "conclusively" that it does not, and some hedge and say it only works in certain instances.
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