early Applications
For centuries, societies have sought to reconcile culpability with insanity. In the Roman empire, individuals found non-compos mentis,” which is Latin for “without mastery of mind” (Borom 1999) were found not guilty. Roman legislators modeled policies based on the assumption that responsibility follows capacity.
The first official application of the insanity defense arose during the 18th century in Great Britain. In Rex v. Arnold, Judge Tracy, a prominent figure in the British court system, advised the jury to acquit a man if evidence indicated he was “a man totally deprived of his understanding and memory, and doth not know what he is doing, no more than a brute, or a wild beast, such a one is never the object of punishment” (PBS 2017). The court’s ruling marked the first attempt to make accommodations for those with lesser intellectual abilities.
Modern Applications
The M’Naghten Ruling
The roots of the modern insanity defense derive from developments in the British court system that led to the M’Naghten ruling. In 1843, a Scottish man named Daniel M’Naghten, who suffered from delusions and paranoia, traveled to London with the intent of assassinating the Prime Minister of England. Under the false impression that the prime minister was plotting against him, M’Naghten attempted to take his life, but mistakenly killed the prime minister’s secretary instead. Following a trial with the testimony of nine psychological experts, the jury found the defendant not guilty by reason of insanity (PBS 2017). The jury elected to send M’Naghten to a psychiatric treatment facility rather than prison. This decision instituted the precedent of court-ordered treatment as a result of acquittal by the insanity defense (Cotrone 2016). Immediately, the court’s verdict incurred tremendous public outcry. Queen Victoria enlisted the House of Lords to review the case and “protect the public from the wrath of madmen who could now kill with impunity” (PBS 2017). As a result, the convocation released the M’Naghten rule, which established that:
"[T]o establish a defense on the ground of insanity, it must be clearly proved that, at the time of committing the act, the party accused was labouring under such a defect of reason as to not know the nature and quality of the act he was doing; or if he did know it; he did not know he was doing something wrong" (Robin 1997).
The M’Naghten rule evaluates a defendant’s cognitive ability to discern right from wrong (Robin 1997). The test stems from the idea that an individual’s mental illness may impair their ability to understand their own actions. Following its initial introduction to the British criminal justice system, the rule quickly became entrenched in the nation’s law and practice. Soon after, the M’Naghten rule inspired similar variations of the legislation in the the American legal system.
However, opponents of the right and wrong test argued that it relied too heavily on the cognitive component of the act. Individuals contended that the test failed to account for other relevant factors such as “the existence or classification of mental defect” and volitional abilities “such as the actor’s ability to will, control, or appreciate the consequences of his acts” (Grachek 2006). As a result, actors who possess the cognitive ability to comprehend their conduct are deemed guilty, regardless of whether they possessed the ability to control their conduct. M’Naghten fails to account for varying degrees of volitional ability. Instead, the rule declares than an individual’s sanity is solely determined by their ability to discern the morality of an action.
The Irresistible Impulse Test
"The defendant should not be held criminally liable for their actions that broke the law, because they could not control those actions, even if they knew them to be wrong" (Cotrone 2016).
Dissension surrounding the M’Naghten rule fueled the development of more comprehensive definitions of legal insanity. The Irresistible Impulse Test emerged as an alternative to M’Naghten (Cotrone 2016). The Irresistible Impulse Test is used to determine whether a defendant was unable to resist the urge to commit a criminal act. The test asserts that individuals who lack the volitional capacity to resist wrongful actions cannot be considered blameworthy.
However, again, the test was met with significant criticism. Dissenters argued that the narrow scope of the test only acquits individuals with the complete inability to control their actions. In doing so, it leaves no room for individuals whose agency is intact, but whose cognitive understanding of morality is inhibited.
The Model Penal Code
"A person is not responsible for criminal conduct if at the time of such conduct as a result of mental defect or disease he lacks substantial capacity either to appreciate the criminality [wrongfulness] of his conduct or to conform his conduct to the requirements of law" (American Law Institute, 1962).
The American Law Institute acknowledged the deficiencies present in all preceding standards. In 1962, the ALI released the Model Penal Code in an attempt to create a single, unified code of law. The Model Penal Code applies when a defendant either could not understand the nature of his or her actions or was unable to confirm his or her actions to the law. The statute marked the first attempt to compromise on previous definitions of insanity by accommodating for volitional and cognitive dimensions of behavior.
However, the Moral Penal Code was met with significant criticism. Individuals asserted that the legal terminology associated with the test was too broad to be applicable.
the Hinckley Case
The Hinckley case served as an additional “catalyst for congressional reform” (Robin 1997). In 1976, John Hinckley attempted to assassinate President Ronald Reagan. The jury found Hinckley not guilty by reason of insanity under the conditions of the Moral Penal Code and acquitted him of all 13 charges of assault, murder, and weapon possession (PBS 2017). Following this decision, public outrage ran rampant. Individuals expressed outrage over the courts decision. Individuals questioned how the Moral Penal Code’s requirement that states an individual must “lack significant capacity” was determined regarding Hinckley. They argued that the vague provisions of the stature enabled a guilty man to be acquitted. As a result, some congressional members called for a complete ban of the insanity defense. Public discontent with the unclear provisions of the defense simmered American people.
Today
Today, individual states remain heavily polarized regarding their respective policies. The future of the insanity defense remains in question as “the U.S. Supreme Court has not finally ruled on the constitutionality of a complete insanity ban” (Rolf 2006). In 1979, Montana moved to abolish the defense completely and several other states (including Idaho, Utah, and Montana) followed suit. Meanwhile, other states have adopted a variety of policies according to individual decisions. There is no uniform insanity test employed across the nation. The working legal definition of insanity remains elusive and contested.