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When Mental Illness & the Law Collide: Part 3

Updated: May 11

Criminal Responsibility (Insanity)

The insanity defense has been plagued by myths and misunderstandings since its beginnings [2]. As introduced in Part 2, insanity is fundamentally different from competence in several ways. First, insanity claims are rare. The general public tends to believe the insanity defense is commonly used. This is due, in part, to widespread media coverage when a defendant attempts the defense, particularly if the crime is well known. Similar to the phenomenon that occurs with mass shootings, the media coverage leads to a false belief that such occurrences are more common than they actually are. In reality, the best estimates suggest that less than 1% of criminal cases invoke the insanity defense and only about 25% of those are successful [1] [3].

Second, whereas competence is a question of the defendant’s present state of mind, insanity focuses on the defendant’s state of mind at the time the crime was committed. More specifically, the sanity issue closely scrutinizes whether the person, at the time the crime was occurring, appreciated what they were doing and that it was wrong. The ultimate question for the court is to determine if the defendant should be held criminally responsible for their actions.

Like competence to stand trial, the insanity defense has a rich legal history and, like competence, it is vitally important to assuring justice in the legal process. At the heart of the issue is free will. The resulting question is if the defendant had the ability to knowingly form the intent to commit a wrongful act. This fundamental issue of whether a person has sufficient capacity to know what they are doing dates back to the beginning of human history. For example, ancient Jewish rabbis established several rules for what was allowable when a person was considered insane. Other references in the Old Testament of the Bible allude to insanity being present and that there may have been some rules for how the issue was to be addressed (see Joshua 20:1-9 for an example).

The modern legal precedent for establishing and responding to insane criminal defendants dates back to at least 1843 and English Common Law when Daniel M’Naghten attempted to assassinate the English Prime Minister. While operating under an obvious delusion, he instead killed his Secretary. This case effectively established the first legal standard for determining criminal responsibility. The English House of Lords opined: “Every man is to be presumed to be sane, and … that to establish a defense on the ground of insanity, it must be clearly proved that, at the time of the committing of the act, the party accused was laboring under such a defect of reason, from disease of mind, and not to know the nature and quality of the act he was doing; or if he did know it, that he did not know he was doing what was wrong.”

In simple and contemporary language, this means the person suffered from a mental condition that rendered them unable to know right from wrong. Thus, it is often referred to as the “right-wrong” test.

As with many matters of law and order, the insanity defense has been challenged and revised over the centuries. The very permissive Durham Rule was established in New Hampshire in 1871, but due to many complications, it fell out of favor quickly. In fact, New Hampshire remains the only American state to continue to use this standard. In 1962, lawyers from the American Law Institute (ALI) proposed a new standard called the Model Penal Code. This standard sought to correct and clarify some of problems in former standards. By the 1970s, this more comprehensive standard was widely adopted in many states.

However, in 1981, John Hinckley attempted to assassinate President Reagan and was found Not Guilty by Reason of Insanity. The public was outraged, believing that Hinckley was unjustly acquitted and that the insanity defense was too easily achieved. In response to immense public pressure, the Insanity Defense Reform Act made the already difficult federal standard even more challenging; many states followed suit by abandoning the Model Penal Code in favor of much stricter M’Naghten Rule. Several other states even abolished the insanity defense entirely (over time, this has raised a unique set of questions. See Kahler v. Kansas that the United States Supreme Court is currently considering).

While Illinois retained the ALI’s Model Penal Code, the Missouri Revised Statutes [4] use a slightly modified version of the M’Naghten standard: “A person is not responsible for criminal conduct if, at the time of such conduct, as a result of mental disease or defect such person was incapable of knowing and appreciating the nature, quality, or wrongfulness of such person’s conduct.” As the legal definition implies, the presence of a sufficient mental condition (“mental disease or defect”) is a necessary, but not sufficient component of an insanity defense. While it would seem reasonable to assume that “mental disease or defect” is simply and old English version of what is now called mental illness, the translation is not that simple.

In State of Missouri vs. Garrett (1965), the Supreme Court of Missouri was faced with an interesting question. The outcome was a clarification of exactly what “mental disease or defect” was intended to mean. In their opinion, the Justices explained that mental disease or defect need not be a specific medical classification (diagnosis), but “merely…a mind sufficiently disordered to cause the results indicated.”

More often than not, however, mental illness is the mental disease or defect that is present in insanity cases. It is notable that the presence of a mental health diagnosis does not, in and of itself, mean a person is in legal insane. As the statute outlines, the mental disease or defect must have resulted in the sufferer being “…incapable of knowing and appreciating the nature, quality, or wrongfulness” of their actions.

As the aforementioned small percentages of successful acquittals imply, it is far more common than not that a mentally ill defendant is determined to know and appreciate the nature, quality and wrongfulness of their actions even though they are mentally ill; thus, they are tried, convicted and sentenced as any other defendant would be. In these cases, mental illness does not absolve them of accountability or punishment under the law. It is only when one has a mental illness that sufficiently disorders the mind and that illness results in them being incapable of knowing and appreciating the nature, quality and wrongfulness of their actions that an insanity verdict can be assigned. 

Each of these components (i.e. mental disease or defect, knowing and appreciating, nature, quality, and wrongfulness) has been the subject of a great deal of legal and psychological analysis and research. Many scholars and professionals over the course of centuries have labored in an effort to create a workable and understandable framework for mental health and legal professionals. Copious amounts of writings, handbooks and professional trainings are part of the routine preparation for forensic professionals seeking to bridge these two disciplines and assist the court with the complex questions that are associated.

Since mens rea (or “guilty mind”) is a core requirement to be convicted of a crime, the court is tasked with answering the difficult question about whether the defendant had the ability to and in fact did form the knowing intent to commit the crime. The defendant is ultimately arguing that were it not for the influence of the mental disease/defect, the crime would not have happened. When this argument is raised, the statutes require the appointing of qualified professional to examine the defendant and to provide the court with an opinion about criminal responsibility.

One of the most pervasive myths involving the insanity defense is that acquittees are released both from accountability for their crime(s) and from just punishment. Put another way, they ‘get off scot free’ [5] [6]. This was the source of outrage in the Hinckley verdict and many since then. In truth, when a criminal defendant is found not guilty by reason of mental disease or defect (“insane”), they are almost invariably committed to a forensic psychiatric facility where they are provided treatment for their mental illness. It is very uncommon for an acquittee to be released without any oversight or conditions placed upon them [1].

Although the duration of treatment varies by jurisdiction, many acquittees spend more time in a psychiatric facility than they would have spent in prison had they been convicted of the crime. In Missouri, for example, the commitment for an NGRI acquittee is indefinite [3]. In Illinois, the acquittee is given a Thiem date – or maximum date of confinement. It is calculated by using the maximum sentence they would have received if found guilty of the ‘worst’ crime with which they were charged. Again, John Hinckley is the quintessential example. Although he had been considered stable and not dangerous decades ago, he was not released until September 2016. Even then, there was much public protest. Many acquittees are eligible for conditional release under a specific set of circumstances, but there are no guarantees, as Hinckely can attest!

The myths surrounding the insanity defense may impact attorneys as well, which could lead them to advise their clients with well-intended, but inaccurate information. For example, the client may be led to believe that an insanity finding will result in a quicker release date, only to be surprised when they are detained for a similar or longer duration [7] and are subject to more stringent conditional release criteria if and when they are eligible [3]. Attorneys and their clients should give careful consideration to these realities before entering an insanity defense.

  1. Huss, M. T. (2014). Forensic Psychology: Research, Clinical Practice, and Applications (2nd Ed.) 167-214.

  2. Perlin, M. L. (2017). The Insanity Defense: Nine Myths that Will Not Go Away in The Insanity Defense: Multidisciplinary Views on Its History, Trends, and Controversies (Mark D. White, Editor). 3-22.

  3. Dirks-Linhorst, P. A. & Kondrat, D. (2012). Tough on Crime or Beating the System: An Evaluation of Missouri Department of Mental Health’s Not Guilty by Reason of Insanity Murder Acquittees. 16(2) Homicide Studies, 129–150.

  4. Mo. Rev. Stat. §552.030 (2011)

  5. Brakel, S. J. (1988). After the Verdict: Dispositional Decisions Regarding Criminal Defendants Acquitted by Reason of Insanity. 37(2), DePaul Law Review 181-258.

  6. Steadman, H. J. (1982). Mentally disordered offenders: A national survey of patients and facilities. 6(1) Law and Human Behavior, 31-38.

  7. Rodriguez, J. H., et al. (1983). The insanity defense under siege: legislative assaults and legal rejoinders. 14(2) Rutgers Law Journal 397–430.

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