Insanity Defense Evaluations
Basic Procedure and Best Practices

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.

Malingering
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.)

Conclusions
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)