The insanity defense existed long before psychiatry1; references to it can be found dating back to biblical times. The Babylonian Talmud refers to the insanity defense in the statement: “It is an ill thing to knock against a deaf mute, an imbecile, or a minor. . . . [I]f they wound others they are not culpable.”
The insanity defense represents a prominent symbol of the relationship between law and psychiatry.2 Despite the fact that it is infrequently raised and seldom successful, the insanity defense is the subject of intense legal and public scrutiny. Psychiatrists are often called on by the criminal justice system to evaluate a defendant’s sanity—a forensic evaluation that requires significant training and expertise. This article provides a brief overview of the basic principles for evaluating a criminal defendant’s sanity at the time of an offense.
Insanity standards
In 1981, John Hinckley was found not guilty by reason of insanity (NGRI) for his attempted assassination of President Ronald Reagan. Public outrage about the verdict led to demands for reform. As a result, the Federal Insanity Defense Reform Act of 1984 narrowed the insanity standard in federal jurisdictions. The revised federal standard is a McNaughtan standard with the requirement of a severe mental disease or defect at the time of the act: “At the time of the commission of the acts . . . the defendant, as a result of severe mental disease or defect, was unable to appreciate the nature and quality or the wrongfulness of his acts.”3
The majority of jurisdictions in the United States use a similar insanity standard that addresses only knowledge of wrongfulness. A minority of states add some variation of the irresistible impulse test, where evidence of volitional impairment may be considered. Approximately 1% of defendants who are charged with a felony plead insanity, and only 15% to 25% of those who plead insanity are actually found NGRI.4 Juries are significantly less likely to render an insanity verdict than are judges.
In 2006, the US Supreme Court considered a case that involved the insanity defense, Clark v Arizona.5 While the Court did not make any substantive rulings about the criteria for an insanity defense, it provided important insights into its current attitudes on the issue. The Court reaffirmed the notion that states are free to define their own insanity standards. Furthermore, the Court recognized that forensic psychiatrists must move from methods and concepts designed for treatment to legal concepts relevant to sanity. This “leap” from one discipline to another requires cautious, objective judgment. Thus, it is recommended that forensic psychiatrists follow a standard evaluation procedure designed to maximize objective reasoning.
Insanity defense evaluation procedure
Before beginning an insanity defense evaluation, the psychiatrist should determine whether he or she has the proper knowledge, skill, experience, training, or education.6 Once the qualification issue has been resolved, the psychiatrist should obtain the exact legal insanity standard used in the jurisdiction at the time of the crime. This standard can be obtained from the court, prosecutor, or defense attorney who referred the defendant for the evaluation.
The next step is learning the facts of the case by reviewing all relevant sources of information. Table 1 gives a checklist that includes important collateral information.
The defendant’s records should be reviewed before the evaluation because these records may contain critical information about the defendant’s mental state shortly before, during, or after the offense. Some defendants are hospitalized in a psychiatric unit after committing the crime or placed in a mental health unit of a jail. If the defendant does not sign a release for these records, a court order is needed to obtain them. Victims, witnesses, and police often record detailed statements after a defendant has been arrested. In some cases, police make a videotape of a defendant’s interrogation. Such evidence is a rich source of information about the defendant’s mental state at the time of the offense. All statements and recordings should be reviewed for indications that the defendant was behaving bizarrely, intoxicated, hallucinating, or delusional at the time of the offense. If statements are not available, a personal interview with the victim(s) or key witnesses should be attempted.
