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This article argues that mental illness should no longer be the basis for a special defense of insanity. Instead, mental disorder should be considered in criminal cases only if relevant to other excuse doctrines, such as lack of mens rea, self- defense and duress, as those defenses have been defined under modern subjectively-oriented codes. With the advent of these subjectively defined doctrines (a development which, ironically, took place during the same period that insanity formulations expanded), the insanity defense has outlived its usefulness, normatively and practically. Modern official formulations of the defense are overbroad because, fairly construed, they exculpate the vast majority of people who commit serious crime. The most prominent alternative to the official tests–the irrationality threshold–is also flawed because it is based on the unprovable assumption that irrational people are less able to act for good reasons. Acquitting only those who lacked mens rea due to mental dysfunction or who acted on delusions that, if true, would sound in self-defense or duress better captures the universe of people who should be excused because of mental illness. This approach would also enhance the image of the criminal justice system, improve treatment of those with mental illness, and reduce the stigma associated with being mentally ill.



Insanity should be eliminated as a separate defense, but that the effects of mental disorder should still carry significant moral weight. More specifically, mental illness should be relevant in assessing culpability only as warranted by general criminal law doctrines concerning mens rea, self-defense and duress.

Acceptance of blameworthiness as the touchstone of the criminal law means that individual culpability must be assessed. That is where the kind of inquiry the insanity defense mandates comes into play. It is meant to help us decide whom among those who commit criminal acts deserve to be the subject of criminal punishment.10

The central assertion of this article, however, is that the insanity defense does not adequatelycarryoutthisdefinitionaltask. Atleastinitsmodernguises,theinsanitydefenseis overbroad. Instead, mental disorder should be relevant to criminal culpability only if it supports an excusing condition that, under the subjective approach to criminal liability increasingly accepted today, would be available to a person who is not mentally ill. The three most prominent such conditions would be: (1) a mistaken belief about circumstances that, had they occurred as the person believed, would amount to a legal justification; (2) a mistaken belief that conditions exist that amount to legally-recognized duress; and (3) the absence of intent to commit crime (i.e., the lack of mens rea defined subjectively, in terms of what the defendant actually knew or was aware of).

Before justifying this position, some examples of how it would apply in well-known actual and hypothetical cases should be provided. Take first the famous M'Naghten case, from whence much of current insanity defense jurisprudence derives.11 In 1841, Daniel M'Naghten killed the secretary of Prime Minister Peel, apparently believing the secretary was Peel and that killing Peel would bring an end to a campaign of harassment against him.12 He was found insane by the trial court judges. Whether M'Naghten would have been acquitted under the proposed approach would depend upon whether he believed the harassment would soon lead to his death or serious bodily harm and whether he thought there was any other way to prevent that occurrence. Because in his paranoid state he feared he would be assassinated by his enemies and had on several occasions unsuccessfully applied to the police for protection,13 he may have had such a defense. If, on the other hand, the circumstances in which he thought he was involved would not amount to self- defense, no acquittal would result14 (although a conviction of manslaughter rather than murder might have been appropriate, analogous to the result under the modern theory of “imperfect” self- defense as it has developed in connection with provocation doctrine).

Now consider the case of John Hinckley, who convinced a jury he was insane when he tried to kill President Reagan.15 If, as even his defense attorneys asserted, John Hinckley shot President Reagan simply because he believed Reagan's death would somehow unite him with 

actress Jodi Foster,16 he would be convicted under the proposed approach. Regardless of how psychotic Hinckley may have been at the time of the offense, he would not have an excuse under the proposed regime, because killing someone to consummate a love affair is never justified, nor is it deserving even of a reduction in charge.

Two other recent cases furnish additional exemplars. Jeffrey Dahmer killed and cannibalized thirteen individuals. The jury was right to convict him.17 As sick as his actions were, even he never thought they were justified, and he would not be excused under the proposal. Lorena Bobbitt, who cut off her husband's penis because he repeatedly beat her, was found insane.18 Whether she would have a complete defense under the proposal would depend, as it would with Daniel M'Naghten, on the extent to which she thought she had other ways of forestalling the beating and whether the option she chose was disproportionate to that threat. On the facts presented at trial,19 even on her own account her act would probably not be considered necessary by the factfinder, and she would therefore have been convicted of some version of assault.

In these cases, then, whether a defense existed under the proposed approach would depend upon self-defense principles, applied to the circumstances as the defendant believed them to be. Another variety of cases can be analyzed in terms of a similarly subjectified version of 

duress, which traditionally has excused crimes that are coerced by serious threats to harm the perpetrator. For instance, some people with mental illness who commit crime claim they were commanded by God to do so.20 If the perceived consequences of disobeying the deity were lethal or similarly significant, such a person would deserve acquittal, perhaps even if the crime charged is homicide. On the other hand, contrary to Justice Cardozo's famous hypothetical suggestion,21 the mere fact that the defendant honestly believed God ordained a crime would not automatically be an excuse.22

The third type of excuse that might apply when people with mental illness commit crime-- lack of mens rea–is extremely rare. M'Naghten, Hinckley, Dahmer, Bobbitt and Cardozo's hypothetical defendant all intended to carry out their criminal acts. Indeed, most crimes in which mental illness plays a role are intentional; the person who is so disordered that he cannot form intent is often also so disorganized behaviorally that he is unlikely to be able to carry out a criminal act. Nonetheless, when mens rea is defined subjectively, there are at least four possible lack-of-mens rea scenarios: involuntary action, mistake as to results, mistake as to circumstances, and ignorance of the law.23

First, a person may engage in motor activity without intending it to occur (e.g., a reflex action which results in a gun firing and killing someone). The criminal law typically classifies such events as involuntary acts.24 Although mental disorder usually does not eliminate conscious control over bodily movements associated with crime, when it does (e.g., in connection with 

epileptic seizures), a defense would exist if one accepts the premise that culpability requires actual intent.25

Second, a person may intentionally engage in conduct but intend a different result than that which occurs (such as when firing a gun at a tree kills a person due to a ricochet). Distortions of perception caused by mental illness might occasionally lead to such accidental consequences; for instance, a mentally ill person driving a car may accidentally hit someone because his “voices” and hallucinations prevent him from perceiving the relevant sounds and visual cues. In such situations a subjectively defined mens rea doctrine would absolve him of criminal liability for any harm caused.

Closely related is the situation in which a person intentionally engages in conduct and intends the physical result that occurs, but is under a misapprehension as to the attendant circumstances (such as when a person intentionally shoots a gun at what he thinks is a dummy but which in fact is a real person). Of the various mens rea defenses, mental illness is most likely to play a role here (in what has sometimes been labeled the “mistake of fact” defense). For instance, a person who believes he is shooting the devil when in fact he is killing a person26 or a person who exerts control over property he delusionally believes to be his27 would be acquitted of homicide and theft, respectively, if mens rea is subjectively defined. Another, more subtle example of this type of mens rea defense is most likely to arise in connection with a person who is mentally retarded rather than mentally ill. Like a young child, such a person may kill not realizing that a life has been ended, because of an incomplete conception of what life is; for instance, the offender may believe the victim will rejuvenate like a cartoon character.28 Mens rea, subjectively 

defined, would be absent in such a case because murder requires not only an intentional killing, but also that the offender understands that the victim is a human being who is capable of dying.29

Finally, a person may intentionally engage in conduct and intend the result, under no misapprehension as to the attendant circumstances, but still not intend to commit a crime because of an inadequate understanding of what crime is. There are actually two versions of this type of mens rea requirement. First, the person may not be aware of the concept of crime (as might be true of a three year-old). Second, the person may understand that criminal prohibitions exist but believe that his specific act is legally permissible (such as might occur when a person from a different country commits an act that would be perfectly legal in his culture, although illegal in ours). The first situation might be called “general” ignorance of the law, while the second might be called “specific” ignorance of the law. Outside of the insanity and infancy contexts, neither type of ignorance has been recognized as an excuse for mala in se crimes.30 However, for reasons discussed in more detail later in this article,31 a subjectively defined mens rea doctrine should excuse at least general ignorance of the law, whether or not it is due to mental disability, a position which would excuse those rare individuals who intentionally carry out criminal acts without understanding the concept of good and evil.

In short, the proposal would treat people with mental disorder no differently from people who are not mentally ill, assuming (and this is admittedly a big assumption) a modern criminal justice system that adopts a subjective approach to culpability.



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January 25, 2018

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Tim Wu


Columbia Law School

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