Mental Illness and the Death Penalty

Mental illness and the death penalty have been a controversial topic for decades. The U.S. Supreme Court has found that such executions are unconstitutional. Although public opinion is somewhat mixed and understudied, national societies such as the American Psychological Association oppose executing the mentally ill. The legal system asks mental health professionals to determine a prisoner’s competency for execution. Incompetent prisoners can be medicated so that they can become competent and thus be executed. Many professionals find this practice unethical. In 1986, the U.S. Supreme Court in Ford v. Wainwright determined that it was unconstitutional to execute a prisoner who became mentally incompetent after his conviction. Such an execution was said to “offend humanity” and violate the country’s “evolving standards of decency.” Thus, the execution was a violation of the Eighth Amendment’s prohibition of cruel and unusual punishment. The “evolving standards” guideline, set forth by Trop v. Dulles (1958), is generally measured by factors including the public’s opinion and existing state legislation. For instance, the Court considered it relevant that, at the time of the Ford ruling, no state permitted the execution of the mentally ill. The Court then detailed the common law and historical evidence indicating that executing the mentally ill has long been rejected in American society. Finally, the Court determined that executing the mentally ill serves no state interest and is not a deterrent to crime. As such, it is cruel and unusual punishment. More recent Supreme Court rulings require that defense attorneys investigate and present evidence that would explain the defendant’s conduct (e.g., if his or her crime was related to mental illness) or lead the jury to reject a death penalty. Thus, the Supreme Court has taken several measures to protect mentally ill defendants.

Social science researchers and mental health professionals have two main roles associated with the execution of the mentally ill. First, social science researchers have conducted research and public opinion polls concerning the execution of mentally ill prisoners. Second, mental health professionals conduct evaluations to determine a prisoner’s competency for execution.

Social Science Research

Public opinion polls have been used to measure the community’s evolving standards of decency. Community support for execution of the mentally ill has not been well studied. Generally, support for the execution of the mentally ill is lower than the level of support for the death penalty in general. For instance, a survey published in 2003 revealed that 13% of respondents favored executing the mentally ill. However, a 2004 study revealed that 57% of respondents favored executing prisoners who had become ill while in prison. This discrepancy may be due to the timing of the illness: The first study could be interpreted to measure support for executing prisoners who were ill at the time of the crime, while the second clearly indicated support for executing prisoners who became ill after the crime. This latter finding seemingly contrasts the notion that executing the mentally ill violates the community’s standards of decency.

Research has also indicated that jurors do not properly consider mental illness when determining whether or not a defendant deserves the death penalty. Although many sentencing statutes list mental illness as a mitigator (i.e., a factor that suggests that the defendant is not deserving of death), research shows that evidence of mental illness instead often leads jurors to sentence the defendant to death. Furthermore, jurors who support the death penalty are more likely than opponents to find a mentally ill defendant guilty and are less likely to believe that the crime was caused by mental illness. Thus, jurors (and the public as a whole) express some disfavor toward mentally ill defendants.

The Role of Mental Health Professionals

The legal system relies on mental health professionals to evaluate defendants for a variety of reasons, including making determinations concerning a prisoner’s suitability for execution. The Supreme Court in Ford was not specific about the criteria that should be used in this determination. Incompetency is a legal term that does not directly translate into psychiatric diagnoses. Legal incompetency is often interpreted to mean that the prisoner suffers from severe mental illness and does not understand the nature of the punishment or why he should suffer it. In general, mental illnesses that affect competency are schizophrenia, bipolar disorders, and delusional disorders. Mental illness, as defined for competency purposes, does not generally refer to personality disorders.

The execution of mentally ill prisoners presents mental health professionals with ethical dilemmas. Ford v. Wainwright prohibits the execution of mentally ill prisoners; however, it is allowable to medicate prisoners so that they become mentally competent. Many mental health professionals and mental health associations do not promote treating mentally ill prisoners so that they may be put to death.

In sum, it is currently unconstitutional to execute mentally ill prisoners, although it is generally acceptable to medicate them so that they become competent to be executed. The Supreme Court has found that the public’s standards of decency forbid such an execution, though some public opinion research contradicts this finding. Despite the finality of the Supreme Court ruling, controversy and ethical dilemmas remain.


  1. Boots, D. P., Cochran, J. K., & Heide, K. M. (2003). Capital punishment preferences for special offender populations. Journal of Criminal Justice, 31, 553-565.
  2. Boots, D. P., Heide, K. M., & Cochran, J. K. (2004). Death penalty support for special offender populations of legally convicted murderers: Juvenile, the mentally retarded and the mentally incompetent. Behavioral Sciences and the Law, 22, 223-238.
  3. Ford v. Wainwright, 477 U.S. 399 (1986).
  4. Slobogin, C. (2000). Mental illness and the death penalty [Electronic version]. California Criminal Law Review, 2, Article No. 3.
  5. Trop v. Dulles, 356 U.S. 86 (1958).

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