How the insanity defence has evolved over the years

The execution of an intellectually disabled Malaysian drug smuggler in Singapore last month reignited a conversation around how people with mental disorders are deemed culpable under criminal law. Singapore has the same grounds for an insanity defence as other nations but the challenge remains in determining culpability. 

Studies indicate that people with mental disorders are disproportionately represented in jails and juvenile facilities with a report by Urban Institute suggesting that more than half of all inmates in the US have a mental illness of some kind.

Most legal systems recognise that a person’s mental illness should be considered when they are tried and sentenced for a crime. Their degree of responsibility is not tied to the illness in and of itself, but instead to the behaviour and mental state that the illness in question produces. Therein lies the complexity of the problem.

In order to understand the confluence of mental illness and the law, we need to look into the history of the insanity defence, the legal definition of mental incapacity, and the challenges associated with juxtaposing retribution against rehabilitation.

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The history of the insanity defence

The concept of defence by insanity has existed since ancient Greece and Rome. While English Common Law adopted a preliminary version of the concept as early as the 13th century, the first complete transcript of an insanity trial appears in 1724. It was around this time that the medical profession started paying attention to the study of insanity, deviating from medieval notions linking insanity to demonic possession.

The landmark moment in the history of the insanity defence came with the M’Naughten case of 1843, which arose from questions put to judges by the House of Lords as to the existing state of law as applicable to the criminally insane. In M’Naughten’s Case, the judges stated that “to establish a defence on the ground of insanity it must be clearly proved that, at the time of the committing of the act, the party accused as labouring under such a defect of reason, from disease of the mind, as 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.”

The standards established by that case are still widely used, including in the UK, America, and India. In 1954, the US Court of Appeals for the District of Columbia expanded upon the M’Naughten test, establishing the Durham rule in its place. Under the Durham test, the accused is not criminally responsible if their unlawful act was the product of a mental deficit.  

However, that standard was criticised for being too broadly applicable and difficult to prove. In 1962, the scope of the Durham test was limited and today, the legal standard for the insanity defence varies from state to state. In 2002, the US Supreme Court prohibited the execution of individuals with mental retardation, but did not define the scope of the term, leaving it to states to determine whether a person suffers from mental retardation or not. This is a universally established problem, wherein judges or juries are responsible for defining what constitutes a disease of the mind.

The UN has also addressed the issue, stating that people who are found to be insane should not be detained in prisons and should be provided with psychological care. Following the standards of the M’Naughten test, Section 84 of the Indian Penal Code also makes exemptions for people who are ‘unsound of mind.’ It states that “nothing is an offence which is done by a person who at the time of doing it, by reason of unsoundness of mind, is incapable of knowing the nature of the act that he was doing or that it was wrong or contrary to the law.” However, the burden of proof under the insanity defence in India lies with the accused.

It is important to note that insanity is a term used only in a legal sense and not a medical one. Therefore, defining what legally constitutes insanity is a crucial aspect to consider.

Definition of insanity

According to Stephen J. Morse, JD, PhD, a Professor of Law and Psychiatry at the University of Pennsylvania, if we are to take mental disorder into account in ascribing responsibility to criminal offenders, then we have to have a legal, not medical, definition for it. The exemption to this is intellectual disability, which can be considered from a medical perspective because, as Morse argues, intellectual disability can be measured relatively well using the IQ test.

In most cases however, Morse asserts that under the law, having a mental disorder is only an excusing condition if it produces an excusing condition, and that simply having one would not meet legal standards. Morse further states that under Western law, there are two generic categories of excusing conditions, one being a lack of rational capacity, and the other, a lack of self-regulatory capacity.

This aligns with the well-established principle, “Actus Non Facit Reum Nisi Mens Sit Rea (an act does not make an offender liable without a guilty mind).” The first concept, namely a lack of rationality, adheres largely with its common-sense definition. According to Morse, this means, “if you can’t get the facts right, you can’t have a reasonably stable preference order, which renders you incapable of reasoning effectively.”

Essentially, if a person lacks rational capacity, it’s not as though they aren’t exercising that capacity, they simply don’t have it. Notably, this is different from your capacity being altered for reasons such as stress, substance abuse or sleep deprivation.

On the other hand, determining lack of self-control is a far more controversial process. Known in the United States as ‘irresistible impulse,’ under this defence, a jury may find a defendant not guilty by reason of insanity if they were suffering from a mental defect that compelled them to commit the criminal offence. Morse argues in this case that the law needs to distinguish between having an urge to do something and not having the ability to control that urge. For example, he cites the oft used ‘policeman at the elbow’ test, in which, a pedophile may have the urge to touch a child but would refrain from doing so because they know a policeman is in the vicinity.

This implies that while the pedophile in question may have an urge to do something wrong stemming from a mental defect, they should be held responsible for acting upon that impulse given that they presumably wouldn’t do so if they were in a situation where they knew they’d get caught. It is therefore their responsibility to stay away from potential criminal situations — in the case of a pedophile that would mean avoiding children whereas for an alcoholic, it would mean avoiding bars and other sorts of temptation. In contrast, if a person was suffering from Tourette syndrome, they would be unable to control their physical and verbal tics no matter how much they may want to.

Insanity defence

The insanity defence in its purest form posits that a person cannot be considered guilty of committing a crime, if they are legally deemed to be unaware that what they did was wrong or were unable to control themselves from doing it. A successful insanity defence would therefore result in an acquittal.

However, there are other important aspects to consider as well. These include diminished capacity, competence to stand trial, temporary insanity and guilt but mentally ill.

Diminished capacity bears some semblance to the insanity defence as both examine mental competence, but the latter is equivalent to pleading not guilty whereas the former is merely pleading to a lesser crime. Diminished capacity for example, could reduce a first-degree murder charge to a manslaughter charge if the defendant lacks the mental capacity to form the appropriate criminal intent for first degree murder.

The establishment of competence to stand trial is a procedural corollary, which, in accordance with due process requirements, a criminal defendant cannot stand trial if they are deemed legally incompetent. Articulated in the US under the Dusky ruling, a defendant is incompetent if they are unable to rationally communicate with their attorney or rationally comprehend the nature of proceedings against them. If the defendant is deemed incompetent, the insanity defence is rendered irrelevant as the defendant cannot stand trial.

Many countries also recognise temporary insanity, which concerns itself with the duration of the mental illness. Temporary insanity is a contested notion and is often conflated with the insanity defence as some jurisdictions argue that insanity at the time of the offence is sufficient to trigger a plea of not guilty by reason of insanity. In most cases, temporary insanity is linked to intoxication or crimes of passion and invoking it successfully can reduce sentencing.  

Finally, courts can rule that a person is guilty but mentally ill. This is not a defence as much as it is an acknowledgement that the offender suffers from some sort of mental disorder and in need of psychiatric support along with incarceration. According to psychiatric researcher Yuval Melamed, this ruling emphasises on punishment and consideration of public safety, which brings us to our next consideration when dealing with mentally ill offenders — that of retribution versus rehabilitation.

Social safety

The intrinsic belief that undermines most criminal justice systems is that they must balance the need to punish people for committing a crime with the need to prepare those offenders to be released into society. According to Morse, sentencing thus “depends on the rationale for punishment in one’s jurisdiction and usually involves both retribution and rehabilitation.”

In terms of the latter, there is significant debate over how the mentally ill should be treated, whether that be in jail or in a psychiatric hospital. If a person is found not guilty by reason of insanity, they are absolved from criminal responsibility but required to be treated in a psychiatric hospital before they are permitted to re-join society.

However, the insanity defence is not nearly as successful as mass media may lead us to believe. According to Frank Schmalleger, author of Criminal Justice: A Brief Introduction, the insanity defence is used in less than 1 per cent of all court cases and, when used, has only a 26 per cent success rate. Similarly in India, researchers looked at 102 Indian High Court cases spanning between 2007 and 2017 in which the insanity defence was employed. They found that in 74 per cent of cases, the court convicted the accused and thus rejected the insanity defence.

The fact that 50 per cent of inmates in the US are deemed to be mentally ill suggests a twin problem of lack of pre-emptive care and inadequate treatment after conviction.

Public spending on mental health averages about 2 per cent of GDP globally, which means that mentally ill people often do not receive the treatment they need during their formative years, which increases their likelihood of committing a crime in the future. Some argue that this creates a cyclical problem in which untreated mentally ill people get sent to jail, where their illness continues to be untreated, which then increases the odds that they will commit crimes after their release.

Suicide by inmates with schizophrenia or manic depressive illnesses is also relatively common. Data collected from New York State jails between 1977 and 1982 showed that half of all inmates who committed suicide had previously been treated for a serious brain disorder.

While some, like Morse, believe that people can be treated just as well in jails as they can in mental hospitals, if resources are allocated better, the data suggest that recidivism rates are lower amongst offenders who were hospitalised by a court order. One study by the Connecticut Psychiatric Security Review Board found that 84 per cent of offenders who were placed in mental hospitals were not rearrested within 12 years of their release. In contrast, according to the National Institute of Justice, almost 44 per cent of criminals released from jail, reoffend before completing their first year out of prison.

In addition to the practical benefits of addressing mental disorders medically, Ahmed Oshaka, President of the World Psychiatric Association, states that the “presence of mental patients in prisons does not only deprive them of their right to proper treatment and care, but also leads to possible maltreatment and stigmatization.” That stigmatism towards mental illness is part of why justice systems tend to steer towards punishment over treatment.

Noted academic Harry J. Steadman, who has conducted several studies on public perception of mental illness, wrote as early as 1977 that the “core public perception of the criminally insane, compared to most people and to mental patients, is that they are unpredictable and dangerous.” As such, according to Morse, there is a huge wedge between social safety and rehabilitation. He states that in the US, the three primary rationales for punishment are retribution (giving people what they deserve), incapacitation (taking them off the streets) and deterrence (scaring other individuals from committing similar crimes).   

The primary concern therefore is ensuring that mentally ill criminals pose no further danger to society, an outcome that can be achieved via treatment, incarceration, or a combination of the two. While the recent case in Singapore illustrated the need to justly and humanely consider the needs of mentally ill offenders, given the challenges of doing so, Morse acknowledges that an international legal consensus is unlikely to materialise anytime soon.