Capital Punishment: Deterrent Effects & Capital Costs

Capital Punishment: Deterrent Effects & Capital Costs
by Jeffrey A. Fagan, Professor of Law & Public Health; Co-Director, Center for Crime, Community, and Law

Capital punishment stirs up fierce debate in the United States. In this essay, Professor Jeff Fagan questions research that supports the long-accepted view of the deterrent effect of capital punishment. States must also come to terms with the fact that each execution can cost between $2.5 million and $5 million, he writes, and ask themselves whether that money can be put to better law-enforcement uses.

Long before the U.S. Supreme Court restored capital punishment in 1976 in Gregg v. Georgia, proponents of the death penalty claimed that executions save lives by deterring murders. This was a popular but unscientific view that was largely untested until 1975, when University of Buffalo Professor Isaac Ehrlich published an influential article asserting that during the 1950s and '60s, each execution "…saved eight innocent lives" by deterring murder. Inspired by an economic model of crime developed by Professor Gary Becker of the University of Chicago, Ehrlich theorized that would-be murderers would choose between illegal and legal behavior based on the threat of execution.

Once his message leached into popular and political discourse on crime, Ehrlich's modest acknowledgments of his study's limitations were quickly lost. Instead, his conclusion had the impact of a sound bite and a bumper sticker rolled into a stick of political dynamite. In the same year, the study was cited by the U.S. solicitor general both in Gregg and in a North Carolina death penalty case. Almost immediately, sharp critiques of Ehrlich's work appeared in academic journals such as the Yale Law Journal disputing his results and offering contradictory findings. In 1978, an expert panel appointed by the National Academy of Sciences strongly criticized Ehrlich's work and rejected its conclusions. Nevertheless, over the next two decades, economists and other social scientists attempted to replicate or reject results using different data, alternative statistical methods, and other twists. The debate produced a standoff.

History is now repeating itself. In the past five years, a new wave of a dozen or more studies have appeared reporting deterrent effects of capital punishment that go well beyond Ehrlich's findings. The estimates of the deterrent effects are far greater, ranging from three to 32 murders deterred for each execution. Some studies claim that pardons, commutations, and exonerations cause murders to increase, while others worry that the time necessary to complete appeals weakens the deterrent effects of execution. Some researchers argue that even murders of passion, among the most irrational of lethal crimes, can be deterred. And one study, by student Professor Zhiqiang Liu, claims that executions not only deter murders, but they also increase the deterrent effects of other punishments such as mandatory minimum sentences for drug crimes and "three strikes" laws for repeat offenders.

The new deterrence research has been discussed favorably and uncritically by national news outlets and has been declared persuasive in leading academic journals and by prominent scholars and jurists. Legal academics, such as Professors Cass Sunstein and Adrian Vermeule, both of the University of Chicago, find the new deterrence evidence "powerful" and "impressive." They couple it with "many decades of reliable data about [capital punishment's] deterrent effects" as the "foundation" of their argument, which holds that since "capital punishment powerfully deters killings," there is a moral imperative to aggressively prosecute capital crimes. Prof. Becker concurs, finding the evidence "persuasive," while Judge Richard Posner brushes aside worries about the possible execution of the innocent as we ramp up executions to achieve even greater deterrent effects. Twice, authors of some of the articles have appeared before the U.S. Congress, stating the case for deterrence.

What are we to make of these claims? The bar is very high when behavioral science makes such strong causal claims. The standards of causal inference in social science—which include the ability by an independent researcher to replicate the original work under diverse conditions; the use of measures and methods that avoid biases from inaccurate "yardsticks" and faulty "gauges"; and the ability to tell a simple and persuasive causal story —are neither technical nor mysterious. They are hallmarks of science that have been recognized by the U.S. Supreme Court in a series of cases that demanded high yet common-sense standards.

When we apply contemporary social science standards, the new deterrence studies fall well short of this high scientific bar. Consider the following: Most of the studies fail to account for incarceration rates or life sentences, factors that may drive down crime rates via deterrence or incapacitation; one study that does so finds no effects of execution and a significant effect of prison conditions on crime rates. Another report shows incarceration effects that dwarf the deterrent effects of execution. Most fail to account for complex social factors such as drug epidemics that are reliable predictors of fluctuations in the murder rate over time. The studies don't look separately at the subset of murders that are eligible for the death penalty, instead lumping all homicides together.

But recent studies that separate capital-eligible homicides - the ones that should be most sensitive to the deterrent effects of execution—from other homicides show no significant changes over time in the rate of capital-eligible homicides in the face of variation in the execution rate. In fact, all but one of the new studies lump all forms of murder together, claiming that all are equally deterrable; the one study that looked at specific categories found that domestic homicides are more deterrable than others, a claim that flies in the face of six decades of theory and research in killings between intimate partners that shows their spontaneity and unpredictability.

The computations in the statistical models are often flawed. For example, simple corrections for large amounts of missing data produce estimates of the deterrent effect of execution that are no different from chance. Using alternate statistical models—models that account for the strong statistical correlation of murder rates from one year to the next—also produces results that show that changes in homicide rates are statistically unrelated to any measure of capital punishment.

Others find that any deterrent effects are specific to Texas, a state that is atypical by (until 2005) denying juries the choice between execution and life without parole. The studies also may unreasonably inflate the effects of execution by cutting the analyses in 1998, thereby excluding later years when homicides declined, as did executions. Still others find the evidence of deterrence very fragile and unstable, with estimates of deterrence changing wildly with even the slightest adjustments or modifications either in measurement or statistical methods. Such instability should signal caution in not only causal inference, but in using these data in policy decisions or law when life and death are at stake.

Finally, the moving parts in the deterrence story are unpersuasive. Execution would have to achieve a marginal cost beyond the threat of lifetime incarceration. There is no evidence that this is the case. Execution would have to occur with sufficient frequency and with widespread knowledge among would-be murderers to create a credible threat considering the types of murders that might be eligible for execution. There is no sign of that, nor does it seem likely.  For example, there were 16,137 murders in 2004, according to the FBI, but only 125 death sentences were handed out, and 59 persons—most of whom were convicted a decade earlier—were executed. There are no direct tests of deterrence among murderers, nor are there studies showing their awareness of executions in their own state, much less in faraway states. There is no evidence that if aware of the possibility of execution, a potential murderer would rationally decide to forgo homicide and use less lethal forms of violence. Murder is a complex and multiply determined phenomenon, with cyclical patterns for distinct periods of more than 40 years of increase and decline that are not unlike epidemics of contagious diseases. There is nothing in the new deterrence studies that fits their story into this complex causal framework.

As a public policy choice, execution requires trade-offs of public resources and investments for state legislators and local prosecutors. The costs of administering capital punishment are prohibitive. Even in states where prosecutors infrequently seek the death penalty, the price of obtaining convictions and executions ranges from $2.5 million to $5 million per case (in current dollars), compared to less than $1 million for each killer sentenced to life without parole. These costs create clear public policy choices. If the state is going to spend $5 million on law enforcement over the next few decades, what is the best use of that money? Is it to buy two or three executions or, for example, to fund additional police detectives, prosecutors, and judges to arrest and incarcerate criminals who escape punishment because of insufficient law-enforcement resources?

Florida, for example, spent between $25 million and $50 million more per year on capital cases than it would have to if all murderers received life without parole. The Indiana Legislative Services Agency estimated that had the state sentenced its death row populations to life without parole, Indiana taxpayers would have been spared approximately $37.1 million.

The burden of these costs is borne by local governments, often diverting precious resources not only from police, but from health care, infrastructure, and education, or forcing counties to borrow money or raise taxes. In the New York paradigm, before the New York State Court of Appeals invalidated the state's death penalty in 2004 in People v. LaValle, death sentences were rare, and there were no executions. As usual, things cost more in New York: Between 1995 and 2004, taxpayers spent about $200 million on the death penalty with no executions. The threshold question for states goes to the heart of the role of deterrence in American capital punishment law, and then joins with the problem of cost.

Justice Byron White, writing in Furman v. Georgia (1972), when the Supreme Court outlawed capital punishment, noted that when only a tiny proportion of individuals who commit murder are executed, the penalty is unconstitutionally irrational. The lessons of Furman once again haunt the present-day reality of most states, when execution is used so rarely as to defy the logic of deterrence. As states across the country adopt reforms to reduce the pandemic of errors in capital punishment, we wonder whether such necessary and admirable efforts to avoid error and the horror of the execution of the innocent won't—after many hundreds of millions of dollars of trying—burden the country with a death penalty that will be ineffective, unreasonably expensive, and politically corrosive to the broader search for justice.