Death Penalty

Most countries have abolished the death penalty. The United States retains the death penalty, although it has attempted to make executions more humane. The Supreme Court has restricted use of the death penalty based on the type of crime and the characteristics of the criminal. Psychologists and other social scientists have conducted research on issues such as whether the death penalty serves as a deterrent, what drives public support for capital punishment, how jurors decide whether to sentence a defendant to life in prison or death by execution, and the possibility of wrongful convictions and executions.

Death Penalty in the International Context

Killing is one of the oldest forms of punishment for criminal behavior, and even today, executions are widespread. Worldwide, shooting, hanging, beheading, lethal injection, and stoning are the most frequently used methods of execution. According to Amnesty International, China currently leads the world in the annual number of executions, followed by Iran, Saudi Arabia, the United States, and Pakistan. The United States and Japan are the only industrialized democracies that still execute criminals. There is a clear international trend toward abolition—between 1985 and 1995, 37 counties abolished the death penalty; and between 1995 and 2005, another 22 countries did so. More than half the countries in the world have now eliminated capital punishment or have ceased to carry out executions. Once abolished, capital punishment is rarely reinstated. Only four countries have reinstated the death penalty (Gambia, Nepal, Papua New Guinea, and the Philippines) after abolishing it, and of those, two have since abolished it again.

American Methods of Execution

The three “modern” methods of execution practiced in the United States—electrocution, poisonous gas, and lethal injection—were developed in an effort to make executions more civilized. Prior to the first electrocution in 1890, hanging was the dominant means of execution in the United States. Hangings were often botched, resulting in gruesome spectacles. Government officials wanted not only to end such spectacles but also to put an end to hangings, which were strongly associated in the public mind with lynching and vigilante justice. Each time a new method of execution was developed—first the electric chair, then the gas chamber, then lethal injection—the main argument was that the new method would be more humane and reliable than its predecessor. Of course, no method of killing is completely humane or reliable. Lethal injection, the method now used in 37 of the 38 states that impose the death penalty, has been challenged on the grounds that it can cause great pain, although the condemned prisoner’s suffering is masked by the paralyzing drugs that are part of the execution process. As some commentators have noted, discussions of whether the death penalty is humane must take into account not only the actual killing of the prisoner but also the long process preceding an execution, including the years spent waiting on death row and the rituals leading up to the execution.

The Supreme Court and the Death Penalty

The constitutionality of capital punishment has been challenged on the grounds that it violates the Eighth Amendment’s prohibition against “cruel and unusual punishment” or the Fourteenth Amendment’s guarantee of “equal protection” under the law. In the 1972 case of Furman v. Georgia, in a 5:4 decision, the Supreme Court held that because of the “uncontrolled discretion of judges or juries,” the death penalty was being “wantonly and freakishly” applied. Capital punishment—as administered at the time—was ruled unconstitutional. However, by 1976, the Court had approved a series of reforms aimed at controlling the discretion of judges and jurors (Gregg v. Georgia). The most important reforms included bifurcated capital trials, where guilt is decided in the first phase and, if the defendant is found guilty, a second “penalty phase” is conducted to determine whether the person found guilty should be sentenced to death or life in prison. More recent decisions by the Supreme Court have placed further restrictions on the penalty of death. The Court has held that mentally retarded murderers cannot be put to death (Atkins v. Virginia, 2002), only juries (not judges) can decide whether a convicted murderer should be sentenced to death, and those who commit their crimes as juveniles cannot be sentenced to death (Roper v. Simmons, 2005). In states that authorize the death penalty, only “aggravated” murder or murder with “special circumstances” is eligible for the death penalty. State laws vary, but examples of capital crimes include murder for hire, murder during the commission of a robbery or rape, murder of a police officer, or kidnapping and murder. The federal crimes of espionage and treason can also result in a death sentence.

The Capital Murder Trial

Many researchers have explored how the unique features of capital murder trials affect guilt and sentencing. One such unique feature is the death qualification process. During jury selection, potential jurors in capital cases are asked whether they would be willing to consider imposing a sentence of death if the defendant is eventually found guilty of capital murder. Prospective jurors who say they would be unwilling to vote for a sentence of death are not permitted to serve on capital juries. Research has shown that the process of death qualification results in a less demographically representative jury (e.g., fewer females and fewer non-White jurors) as well as a jury that is more receptive to the prosecution and more likely to impose a sentence of death. A second distinctive feature of capital trials concerns the penalty phase instructions to jurors. In most states, jurors are instructed to weigh or balance aggravating factors that support a sentence of death against mitigating factors that support a sentence of life. Based on postverdict interviews with hundreds of capital jurors, the Capital Jury Project has found that jurors have great difficulty in understanding both the concept of “mitigation” and the concept of “weighing.” In addition, many jurors often wrongly assume that unless they vote for a death sentence, the defendant will be eligible for parole and may eventually be released from prison. Like the death qualification process, the ambiguity of penalty phase instructions tends to increase the probability of a death sentence.

Deterrence and Death Penalty

Deterrence—the theory that the existence of the death penalty will prevent potential murderers from actually committing murder—was one the earliest justifications for executing criminals. Barbarous forms of execution such as breaking at the wheel, burning at the stake, decapitation, and disemboweling were thought to be especially effective at creating the fear necessary to deter those who might consider committing a capital crime. Despite the intuitive appeal of this theory, research does not support a deterrent effect for the death penalty. The introduction of the death penalty does not suppress murder rates, and its abolition does not cause murder rates to rise. Scores of studies have investigated whether capital punishment has a deterrent effect. These studies have looked at homicide rates in jurisdictions with and without the death penalty (e.g., adjacent states) or examined homicide rates over time when the death penalty is abandoned or reinstated. In examining the possibility of a deterrence effect, social scientists have attempted to control statistically for factors that are known to contribute to rates of violence—for example, size of the police force, number of young males in the population, and unemployment rates. Specific analyses have also been conducted to determine whether only crimes punishable by death (e.g., aggravated murder) are deterred, and studies have been conducted to determine whether it is the actual number of executions (as opposed to whether the death penalty is an available punishment) that deters. The overall finding of more than 40 years of research is that the death penalty does not deter murderers. Although some researchers have found a deterrent effect for some jurisdictions over a specific period of time, other researchers have found what has been called the “brutalization effect”—a small but consistent increase in the number of murders in the weeks following an execution.

Research on deterrence tends to rely on large data sets collected over long periods of time. But the theory of deterrence also relies on a psychological explanation of what happens in the minds of potential killers. For capital punishment to effectively deter, potential murderers would need to believe that there is a high probability of being caught, convicted, sentenced to death, and eventually executed for their crimes. And if the availability of the death penalty is to have a deterrent effect beyond that provided by life in prison, the potential killer would also need to judge the possibility of eventual execution as substantially more frightening than the prospect of spending the rest of his or her life in prison. Even a rational analysis of these probabilities would not necessarily deter a potential killer, and because most murders are committed under the influence of drugs or powerful emotions, it seems implausible that murderers rationally weigh out alternatives.

Public Opinion about Death Penalty

Media coverage often emphasizes that a majority of Americans support capital punishment. It is true that when Americans are asked the general question, “Do you favor or oppose the death penalty for persons convicted of murder?” approximately 66% of respondents indicate their support. This support has fluctuated over time. In 1966, support for capital punishment dropped to 42%, but by 1988, support had risen to 79% of the public. Overall, males are significantly more supportive than females, Whites are more supportive than Blacks, and Republicans are more supportive than Democrats. While responses to a broad question about support for or opposition to the death penalty may give a rough indication of American attitudes at a particular time, such general responses can be misleading. More detailed survey research reveals that support often rests on mistaken assumptions about issues such as cost, fairness of application, or deterrence. In addition, support falls when alternative punishments are mentioned. The public is about evenly divided if respondents are asked to choose between the option of “the death penalty” or “life in prison without the possibility of parole” for “persons convicted of murder.” When the punishment of “life without parole plus restitution” is offered as an alternative to the death penalty, a majority of Americans endorse it.

Wrongful Conviction and Execution

Decisions about who is guilty of capital murder and who should be executed are entrusted to a fallible legal system. The possibility of wrongful conviction and execution of an innocent defendant has always been part of the public debate over capital punishment, but the emergence of DNA as a means of criminal identification has made this argument much more prominent. During the past 30 years, more than 120 people have been released from death row because of new evidence or reanalysis of existing evidence. It is important to note that the number of wrongful convictions exposed by DNA analysis is only a fraction of the total. Such DNA-based exonerations are only possible if biological evidence (e.g., blood, semen, skin cells) has been collected at the crime scene and preserved for later testing. It is impossible to know how many prisoners currently on death row are actually innocent. For most death row inmates, there is clear evidence of guilt. And many who claim to be innocent could be lying. But it is likely that there are also cases where wrongfully convicted death row inmates are unable to prove their innocence because of lack of evidence or lack of resources.

More than 1,000 condemned prisoners have been executed since the reinstatement of the death penalty in 1976. It is impossible to know exactly how many of these prisoners were actually innocent. Once a prisoner has been killed, courts rarely entertain claims of innocence, and lawyers, investigators, and journalists turn their attention to cases where possibly innocent prisoners can still be saved. Despite the difficulty of conclusively proving wrongful executions, there are a handful of cases where there is persuasive evidence that the wrong man was executed (e.g., Ruben Cantu, Gary Graham, Larry Griffin, James O’Dell, Leo Jones). The reality of wrongful conviction and wrongful execution raises the issue whether retention of the death penalty is so valuable that it justifies occasionally sending an innocent person to death row and perhaps to the execution chamber.

If the decision to retain or abandon capital punishment was based solely on research findings, it would have been abolished long ago. However, like many important social policies, the decision is driven by emotional and political as well as empirical considerations.


  1. Atkins v. Virginia, 536 U.S. 304 (2002).
  2. Bedau, H. A. (2004). Killing as punishment. Boston: Northeastern University Press.
  3. Costanzo, M. (1987). Just revenge: Costs and consequences of the death penalty. New York: St. Martin’s Press.
  4. Dow, D. R. (2005). Executed on a technicality. Boston: Beacon Press.
  5. Furman v. Georgia, 408 U.S. 238 (1972).
  6. Gregg v. Georgia, 428 U.S. 153 (1976).
  7. Myers, B., & Greene, E. (2004). The prejudicial nature of victim impact statements: Implications for capital sentencing policy. Psychology, Public Policy, and Law, 10, 492-515.
  8. O’Neil, K. M., Patry, M. W., & Penrod, S. D. (2004). Exploring the effects of attitudes toward the death penalty on capital sentencing verdicts. Psychology, Public Policy, and Law, 10, 443-470.
  9. Osofsky, M. J., Bandura, A., & Zimbardo, P. G. (2005). The role of moral disengagement in the execution process. Law and Human Behavior, 29, 371-393.
  10. Roper v. Simmons, 543 U.S. 551 (2005). Zimring, F. E. (2003). The contradictions of American capital punishment. New York: Oxford University Press.