Insanity Defense Evaluations - Basic Procedure and Best Practices

December 1, 2008

The insanity defense represents a prominent symbol of the relationship between law and psychiatry. Despite the fact that it is infrequently raised and seldom successful, the insanity defense is the subject of intense legal and public scrutiny.

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.

The defendant should be interviewed as soon as possible after the offense. However, defendants are often evaluated for sanity many months after the offense. Early evaluation reduces the likelihood that the defendant will have been coached about the legal criteria for insanity. Furthermore, as time passes, defendants may change their account of the offense because of unconscious distortion or attempts to malinger insanity.

At the outset of the interview, the defendant must be informed of the purpose of the evaluation, who will receive a report of the evaluation, and the lack of confidentiality. A careful psychiatric history should be obtained from the defendant, including inquiry into the nature of hallucinations, delusions, and past treatment efforts. The psychiatrist should request a detailed account of the crime by the defendant. It is helpful to have the defendant give a step-by-step account of his actions beginning 1 to 2 days before the offense. The account should include details on psychiatric symptoms, medication adherence, and use of intoxicants.

Formation of the insanity defense opinion
Opinion formation is the most challenging aspect of the insanity defense evaluation. The underlying reasons for the opinion must be clearly explained. Having a logical rationale for the opinion is critical. Before formulating the opinion, the psychiatrist should strive for a detailed understanding of the defendant’s thinking and behavior before, during, and after the offense. It is important to consider evidence of mental illness (during the evaluation, in the past, and at the time of the offense), possible psychotic and nonpsychotic motives for the offense, and the defendant’s criminal history and personality type.

The psychiatrist should assess whether the defendant’s inability to know the wrongfulness or refrain from the act was the result of mental illness or other factors, such as voluntary intoxication or rage. It may be helpful to conceptualize insanity opinion formation as consisting of a 3-step process:

• First, the question of whether the defendant suffered from a mental disease or defect at the time of the offense must be answered.
• Next, capacity evidence must be addressed-that is, knowledge of wrongfulness of the offense at the time in question.
• Finally, the issue of causation must be addressed-what was the relationship between the defendant’s mental disease and criminal behavior?

Mental disease evidence
Virtually all insanity standards require the presence of a “mental disease or defect” at the time of the offense. Mental disease or defect is a legal term and is not defined in DSM. However, the American Psychiatric Association Position Statement on the Insanity Defense from 1982 does provide some guidance: “Another major consideration in articulating standards for the insanity defense is the definition of mental disease or defect. . . . [M]ental disorders leading to exculpation must be serious. Such disorders should usually be of the severity (if not always of the quality) of conditions that psychiatrists diagnose as psychoses.”1

In a study of 5175 sanity evaluations, findings of insanity by expert opinion were significantly associated with the defendant having psychosis and having had psychiatric hospitalizations.7 Similarly, in a study of 8138 defendants who pleaded insanity, those with a major mental illness and who had had psychiatric hospitalizations (suggesting more severe illness) had higher rates of acquittal by reason of insanity.8 Studies of persons who were found NGRI indicate that a psychotic level of illness is usually required.9-11 Most courts have held that diagnoses such as schizophrenia, major depressive disorder, and bipolar disorder qualify as a mental disease for the purpose of insanity.

Diagnoses such as personality disorders, paraphilias, and voluntary sub­stance intoxication do not usually qualify. Although some state statutes provide guidance on which disorders are excluded, the final decision rests with the trier of fact. The concept of mental disease as used in legal standards for insanity is “generally construed to refer to a disorder of fixed or prolonged nature in contrast to any transitory emotional state.”12 Thus, temporary displays of rage or aggression unassociated with a major mental disorder are unlikely to qualify as mental disease. The term “mental defect” most commonly refers to mental retardation or some developmentally acquired disorder of intellect. The finding of a mental defect typically requires intellectual impairment in the range of at least mild mental retardation.

Capacity evidence
All US insanity standards (with the exception of the New Hampshire Doctrine) address the defendant’s knowledge of wrongfulness of the offense at the time of the act. Table 2 presents a list of behavioral evidence that warrants consideration by the psychiatrist when evaluating a defendant’s capacity to recognize the wrong­fulness of his criminal act.

When evaluating knowledge of wrongfulness, the psychiatrist should carefully analyze the defendant’s behaviors, statements, and motives. For example, hiding evidence, lying about the offense, and fleeing from the police all suggest that the defendant knew that his behavior was legally wrong. In contrast, committing a crime with no rational motive, making no effort to avoid detection, and making no effort to flee may suggest a lack of knowledge of wrongfulness. As noted, the defendant’s statements during or after the offense often provide critical insight into the defendant’s knowledge of wrongfulness. Statements made by the defendant months later that he knew the act was wrong are helpful, but care must be used to determine whether the defendant can accurately recall his thinking at the time of the crime.

Elucidating the defendant’s motive for committing the offense is critical. The psychiatrist must consider the presence of a rational alternative motive for the offense that did not flow from a mental disease or defect. For example, “ordinary” criminal motives such as revenge or anger must be considered in the case of a jilted wife who kills her estranged husband. Other common, nonpsychotic motives for criminal behavior include profit, jealousy, and greed. In contrast, a crime without an apparent motive (eg, random killing of a stranger) may provide support for a valid insanity defense.

Appellate court interpretations of the word “wrong” can become a pivotal issue. Before the McNaughtan case, jury questions never addressed the concept of moral versus legal wrongfulness. The McNaughtan case raised the question of the defendant’s knowledge of moral, as opposed to legal, wrongfulness. Legal wrongfulness is defined as the defendant’s concrete understanding at the time of the offense that his act is against the law. Moral wrongfulness is more abstract, and can be further separated into subjective moral wrongfulness, and objective moral wrongfulness. Subjective moral wrongfulness refers to the defendant’s own belief that his act was morally justified-despite his knowledge that the act was against the law.

In contrast, objective moral wrong­fulness refers to the act of a defendant who, as a result of a psychiatric disorder, lacks the capacity to know that society considers his act to be wrong. In the Yates case, the legal test in Texas was: “at the time of the conduct charged, the actor, as a result of severe mental disease or defect, did not know that [her] conduct was wrong.”13 In the Yates trial, both defense and prosecution experts agreed on 3 issues14:

• Mrs Yates suffered from a mental disease.
• Mrs Yates knew that her conduct was against the law/
• A subjective moral wrongfulness issue had to be considered.

This final point referred to the evidence that Mrs Yates had a delusional belief that her children were not being raised “righteously” and would “burn in hell.” As their mother, her priority was to “save” them.

In a minority of jurisdictions in this country (16 states), the insanity standard allows for consideration of the capacity to conform one’s conduct to the requirements of the law. This is sometimes referred to as the volitional prong of the insanity defense. Some states refer to it as the inability to adhere to the right, inability to control one’s conduct, or irresistible impulse.

The volitional arm of the insanity defense is the subject of some contro­versy in psychiatry. When a psy­chiatrist is called on to form an opinion on this issue, he should be forthright about the limitations inherent in making this determination. Some guidelines from the literature may be of assistance, but the psychiatrist should bear in mind that “the notion that mental disorder can cause conduct to become completely involuntary or unintentional is questionable, given current thinking in the behavioral sciences.”15

The loss of volitional capacity must be experienced as an internal, non-negotiable demand. Furthermore, the defendant usually experiences the loss of volitional capacity with a sustained negative effect on his day-to-day functioning, which may be verified by collateral sources. If the loss of control is based on a genuine mental illness, it may have a disinhibiting or disorganizing ef­-fect on the individual’s overall, day-to-day functioning. Thus, an emotional state flowing from moments of rage would not likely satisfy this com­ponent of the test.12 The forensic evaluator should ascertain the de­fendant’s capacity to be deliberate, choiceful, and purposeful with regard to the crime, as well as his capability to resist impulses in other areas of life.

Because of limitations inherent in assessing volitional control, psychiatrists should strive for enhanced rigor and consider the defendant’s ability to defer the offense. For example, a defendant may demonstrate considerable restraint by waiting until the victim is alone, or waiting for circumstances that are advantageous for committing a crime. A defendant’s claim that “I couldn’t control myself” should not be taken at face value. The examiner must carefully investigate the cause of the claimed inability to refrain.

Causal relationship between mental disease and lack of capacity
It is critical for the psychiatrist to establish the relationship, if any, between the defendant’s mental disease and the defendant’s criminal behavior by analyzing the defendant’s “awareness of what [he was] doing during the crime and what [his] motivations for actions taken were at that time.”16 The relationship between a defendant’s mental disorder and the crime generally falls into 1 of 5 possible patterns17:

• Pattern 1: Offenders whose crime is a response to psychotic symptoms that are usually delusions or hallucinations.
• Pattern 2: Offenders who commit crimes that are motivated by compulsive desires (eg, sex offenses by those with paraphilias or crimes involving disorders of impulse control).
• Pattern 3: Offenders who have personality disorders and their crime is consistent with a maladaptive pattern of voluntary and knowing behavior.
• Pattern 4: Offenders who have a genuine mental disease; however, it is merely coincidental and unrelated to the crime
• Pattern 5: Offenders who have a mental illness, but the illness was brought on by the crime.

Table 3 lists the common patterns of mental disorder and crime.

Although these offender categories do not resolve the question of sanity, certain inferences can be made; some pattern 1 offenders will meet the legal criteria for insanity. However, this will depend on the facts of each individual case and the relevant legal standards. Pattern 2 offenders are very unlikely to meet insanity criteria, especially in jurisdictions without volitional prongs. Pattern 3, 4, and 5 offenders will not be candidates for an insanity defense.

When evaluating criminal defendants in a forensic setting, the psychiatrist must always consider malingering.16 Although the exact percentage of offenders who attempt to malinger insanity is unknown, empirical data suggest that it is not uncommon for some offenders to feign insanity to avoid criminal responsibility. In a study of criminal defendants, the prevalence of malingering was 8% over 314 consecutive evaluations in a forensic hospital.18 (Readers are referred to Resnick and Knoll19 for a more comprehensive discussion on detecting malingered psychosis and insanity.)

Insanity defense evaluations require the psychiatrist to accurately address:

• The presence of mental disease at the time of the offense.
• Capacity evidence.
• The relationship between the mental disease and the crime.

The US Supreme Court has noted that insanity defense opinions require a “leap” from methods and concepts designed for treatment to legal concepts of criminal responsibility.4 Psychiatrists have a duty to the courts to be sure this leap is sure-footed, accurate, and based on scientific evidence. In addition, it is our responsibility to uphold the “credibility of our profession” by improving our practice in this highly public interaction between psychiatry and law. (Readers may wish to refer to other sources for a more comprehensive guide to the history of the insanity defense and current acceptable forensic psychiatric guidelines.16,20)



1. American Psychiatric Association. The Insanty Defense Position Statement. American Psychiatric Association; 2007. Accessed November 19, 2008.
2. Stone AA. The trial of John Hinckley. In: Stone AA. Law, Psychiatry, and Morality. Washington, DC: American Psychiatric Press; 1984:chap 4.
3. 18 USC §17.
4. Callahan LA, Steadman HJ, McGreevy MA, Robbins PC. The volume and characteristics of insanity defense pleas: an eight-state study. Bull Am Acad Psychiatry Law. 1991;19:331-338.5. Clark v Arizona, 548 US 735 (2006).
6. Federal Criminal Code & Rules. Testimony by experts. Rule 702. St Paul: West Publishing; 1995:263.
7.Warren JI, Murrie DC, Chauhan P, et al. Opinion formation in evaluating sanity at the time of the offense: an examination of 5175 pre-trial evaluations. Behav Sci Law. 2004;22:171-186.
8. Cirincione C, Steadman HJ, McGreevy MA. Rates of insanity acquittals and the factors associated with successful insanity pleas. Bull Am Acad Psychiatry Law. 1995;23:399-409.
9. Nicholson RA, Norwood S, Enyart C. Characteristics and outcomes of insanity acquittees in Oklahoma. Behav Sci Law. 1991;9:487-500.
10. Nestor PG, Haycock J. Not guilty by reason of insanity of murder: clinical and neuropsychological characteristics. J Am Acad Psychiatry Law. 1997;25: 161-171.
11. Cochrane RE, Grisso T, Frederick RI. The relationship between criminal charges, diagnoses, and psycholegal opinions among federal pretrial defendants. Behav Sci Law. 2001;19:565-582.
12. Rogers R, Shuman DW. Conducting Insanity Evaluations. 2nd ed. New York: Guilford Press; 2000.
13. Texas Penal Code § 8.01.
14. Resnick P. The Andrea Yates case: insanity on trial. Cleve State Law Rev. 2007;55:1-10.
15. McSherry B. Voluntariness, intention, and the defence of mental disorder: toward a rational approach. Behav Sci Law. 2003;21:581-599.
16. Giorgi-Guarnieri D, Janofsky J, Keram E, et al; American Academy of Psychiatry and the Law. AAPL practice guideline for forensic psychiatric evaluation of defendants raising the insanity defense. J Am Acad Psychiatry Law. 2002;30(suppl 2):S3-S40.
17. Dietz PE. Mentally disordered offenders: patterns in the relationship between mental disorder and crime. Psychiatr Clin North Am. 1992;15:539-551.
18. Cornell DG, Hawk GL. Clinical presentation of malingerers diagnosed by experienced forensic psychologists. Law Hum Behav. 1989;13:375-383.
19. Resnick P, Knoll J. Malingered psychosis. In: Rogers R, ed. Clinical Assessment of Malingering and Deception. 3rd ed. New York: Guilford Press; 2008:51-68.
20. Knoll J, Resnick P. Insanity defense evaluations: toward a model for evidenced-based practice. Brief Treat Crisis Interven. 2008;8:92-110.

Evidence-Based References
Knoll J, Resnick P. Insanity defense evaluations: toward a model for evidenced-based practice. Brief Treat Crisis Interven. 2008;8:92-110.
Warren JI, Murrie DC, Chauhan P, et al. Opinion formation in evaluating sanity at the time of the offense: an examination of 5175 pre-trial evaluations. Behav Sci Law. 2004;22:171-186