Competence to Stand Trial

The ability of a person charged with a crime to understand the nature and purpose of the criminal proceedings.

Defendants in a criminal trial must have the ability (i.e., the competence) to understand the charges, to consult with an attorney, and to have a rational grasp of the courtroom proceedings. This requirement is a long-standing and fundamental principle of criminal law. Its purpose is to ensure that defendants can participate meaningfully in their own defense. The requirement refers to the defendant's competence at the time of the trial, rather than their psychological state at the time of the alleged offense. Rationality is a key issue in competency determinations. People judged to be incompetent usually lack the ability to understand, communicate, or make rational decisions. The legal requirement, however, does not indicate how judgments about competency should be made. Furthermore, some cases are more complex than others. Consequently, it is possible for a defendant to be competent for certain kinds of legal proceedings, but not for others.

There are a number of questions that evaluators might seek to answer when making a competency determination. Does the defendant understand the charges? Does he appreciate the possible penalties? Does he appreciate the adversarial nature of the courtroom? Can he discuss legal strategy with his lawyer? Can he behave appropriately in the courtroom? Can he provide meaningful testimony in his own defense? The issue of competence can arise at any point during criminal proceedings, and may be initiated by the defense, by the prosecutor, or by the judge. Prior to 1972, defendants found to be incompetent could be confined to mental hospitals for very lengthy periods of time—sometimes for a longer period than they would have served if they had been found guilty. A U.S. Supreme Court ruling in 1972 restricted the length of time a defendant could be hospitalized because of incompetence to stand trial.

Once the question of competence arises, a competency evaluation will be conducted. The evaluation typically takes place in a special hospital or clinic. A number of professionals may be qualified to conduct such examinations, including physicians, psychiatrists, psychologists, and social workers. There are several different psychological tests or procedures designed to assist in the assessment of competence to stand trial. One of these is the Competency Screening Test (CST). It is a 22-item sentence completion test that requires the test-taker to complete sentence stems, such as: “When I go to court, the lawyer will___________.” Answers are scored as indicating competence, question able competence, or incompetence. Total scores are calculated with a cutoff score that indicates possible incompetence. Another assessment test is the Competency Assessment Instrument (CAI). It consists of a detailed face-to-face interview about various aspects of competent functioning, including an appreciation of the charges and an understanding of the various roles of the judge, witnesses, jury, prosecutor, etc.

Theodore Kaczynski was accused in April, 1996 of being the serial bomber who built homemade bombs that killed three people and injured many others between 1978 and 1995. At the beginning of his trial he disrupted the proceedings because of a dispute with his lawyers about his defense. His request to represent himself and an attempted suicide provoked concerns about his competence. The court requested a competency assessment. Kaczynski (also known as the Unabomber) was judged by the psychiatrist who conducted the assessment to be legally competent to stand trial. In her report to the court, the psychiatrist said that Kaczynski was not suffering from any mental defect that could prevent him from understanding the nature of the charges, or from assisting his lawyers in mounting a defense. On the other hand, she noted that he was suffering from paranoid schizophrenia. Ultimately, a trial was averted when he agreed to plead guilty to numerous charges in exchange for a promise that prosecutors would not seek the death penalty during his sentencing. He was sentenced to four life terms plus 30 years with no possibility of parole. The Unabomber case provides a good illustration of a situation in which a psychological disorder did not necessarily harm the defendant's ability to participate meaningfully in the trial proceedings.



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Costanzo, Mark, and Daniel Krauss. Forensic and Legal Psychology: Psychological Science Applied to Law, 2nd edition. New York: Worth, 2015.

Prins, Herschel. Offenders, Deviants, or Patients?: An Introduction to Clinical Criminology, 5th edition. New York: Routledge, 2016.


American Board of Forensic Psychology, .

International Association for Correctional and Forensic Psychology, 897 Oak Park Boulevard, #124, Pismo Beach, CA, 93449, (910) 799-9107,, .