Published On: 25th January, 2024

Authored By: Akshita Singh
University of Allahabad


The insanity defence has long been a controversial and complex aspect of criminal law, providing individuals accused of committing crimes with a unique avenue for legal defence. This abstract explores the conceptual foundations, historical evolution, and contemporary challenges surrounding the insanity defence. It delves into the psychological and legal considerations that underpin the defence, examining the varying standards used to determine insanity across jurisdictions. The abstract also highlights the ethical and societal implications of employing insanity as a defence strategy, considering issues such as the stigma attached to mental illness, public perception, and the potential impact on criminal responsibility. Additionally, it discusses notable legal cases and their outcomes, shedding light on the practical application of the insanity defence. By analysing the multifaceted nature of this defence, this abstract aims to contribute to a nuanced understanding of the interplay between mental health and criminal culpability within the legal system.


The defence of insanity is a highly contentious topic in criminal law. Insanity as a defence is based on both legal and psychological considerations, allowing individuals who are accused of a specific offence to plead insanity as a defence, claiming that they were not criminally responsible for their actions due to a mental disorder or impairment at the time of the offence. This defence raises profound questions about culpability, justice, and the delicate balance between protecting society and acknowledging the complexities of mental health.

Based on the premise that an individual cannot be held accountable for actions taken while mentally incapacitated. This legal plea of mental incompetence or insanity attempts to balance the complexities of mental health. The jurisprudential essence can be found in numerous legal precedents and provisions. The Indian Penal Code recognises that a person is not criminally liable if, at the time of commission of an act, he is suffering from any mental disability or disorder that renders him unable to understand the nature and consequences of his conduct. He is unable to recognise the nature of his behaviour and what he is doing is whether wrong or contrary to the law.

This acknowledgement demonstrates a commitment to a justice system that considers the accused’s mental state as an important factor in assessing guilt or innocence.

The complexity of the plea stems not only from establishing the mental disease but also from persuading the court of its impact on the individual’s ability to recognise the wrongfulness of their actions. Expert psychiatric testimony is crucial in evaluating the accused’s mental state at the time of the offence. As the legal environment changes to include a more nuanced understanding of mental health, India’s insanity plea reflects a continuing conversation between legal principles and appreciation of the severe impact of mental diseases on individual accountability. This defence not only protects the rights of persons facing criminal charges, but it also emphasises the need for a justice system that understands the intricacies of the human mind.


The insanity defence has a long and changing history, influenced by cultural, legal, and medical advances. Here’s a basic historical outline.

In ancient civilizations such as Greece and Rome, there existed a rudimentary awareness that people who were declared mentally sick could not be held accountable for their conduct.

Early legal codes, such as the Code of Hammurabi, recognised mental illness as a mitigating factor in criminal guilt.

 Throughout much of history, mental illness was often attributed to moral failings or supernatural causes. The treatment of mentally ill individuals was often harsh, involving punishment or exorcism rather than medical care.

The 18th and 19th centuries witnessed a shift towards medical explanations for mental illnesses.  Philippe Pinel and William Tuke advocated for humane treatment and acknowledged that mental illness could impair a person’s capability to think rationally.

The beginning of the modern era was marked by the landmark decision of McNaughten’s rule, established in 1843, where it was decided that a person is not criminally liable for any act for which he was labouring under such a defect of the reason that he was unable to know the nature and consequence of the act they were doing, or if they knew, they did not know what was wrong. The legal standard evolved as a result of this insanity defence. The US Penal Code, often known as the Model Penal Code, expands the scope of this defence by establishing a new test known as the irresistible impulse test. However, it was questioned in the instance of Ronald Reagan’s assassination, when some jurisdictions attempted to replace the defence of insanity with an alternative strategy such as a guilty but mentally ill (GBMI) verdict.

This defence now differs globally depending on jurisdiction. Most people preferred psychiatric competence to assess the accused’s mental condition at the time of the alleged offence.

Throughout history, insanity as a defence has evolved from diverse jurisdictions and represents society’s shifting attitude towards mental disease, as a plea of defence via mental health has been given importance in the commission of any crime.


The legal standard of insanity varies by jurisdiction, and becomes a crucial element in determining whether the accused should be held liable for his criminal act.

Wild beast Theory[1]:

The first case that dealt with the defence of insanity was R v. Arnold[2] in which Edward Arnold was tried for killing Lord Onslow. The evidence clearly shows that the accused was suffering from mental disorder.

“If he was under the visitation of God and could not distinguish between good and evil, and did not know what he did, though he committed the greatest offence, yet he could not be guilty of any offence against any law whatsoever.”[3]

Under these circumstances, a person can claim immunity if, due to his unsoundness of mind, he was incapable of differentiating between good and evil and also did not know the nature of the act. This is known as the ‘Wild Beast Test.’

Delusion Test in Hadfield’s case:

The second test evolved from the Hadfield’s case, where defence lawyer persuaded the jury to consider that insanity cannot be confined to total deprivation. He opined that fixed insane delusion should be consider only within the given context and not to affect the total personality of the individual.

Bowler’s case of right and wrong:

Through this case the idea of ‘good and evil’ was replaced by the term ‘right and wrong’. It determines the persons capacity to discriminate between right and wrong to test the insanity of the person. This decision placed more weight on idea of ‘right and wrong’[4].

 McNaughten’s Rule:

The most notable judgement of McNaughten case in 1843 which derives the ‘McNaughten rule’ as a defence in English Criminal Jurisprudence. According to this rule, a person is not legally accountable for their conduct if, at the time of committing the act, they were labouring under such a defect of reason that they were unaware of the nature and quality of the act they were performing or, if they were aware of it, did not know that it was wrong.

In this case, Daniel Mc’Naughten believed that the then Prime Minister Sir Robert Peel, was the only cause of all his issues. So, he decided to assassinate the Prime Minister. However, he confused the Personal Secretary of PM, Mr. Edmond Drummond, as the Prime Minister and killed him.

He attempted to use the defence of insanity, claiming that he was unaware of the negative implications of his actions and was unable to discriminate between right and wrong. The Fifteen Judge Bench was created in the House of Lords to decide on this matter, and while pronouncing their verdict, they laid down several rules that became known as the McNaughten Rules, which were as follows:

  1. If a person has partial delusion and reasonably understands the nature and consequences of their actions, they cannot use insanity as a defence.
  2. Every person is presumed to be sane and prudent
  3. To establish the defence of insanity, a person must demonstrate that their mental state was such that they were unable to determine the outcome of their actions.

It was suggested that in this case, the required mens rea for the murder of Prime Minister is not present rather he was intellectually unconscious of his actions because he was in delusion. The goal of this regulation is to determine who is mentally incapable of making reasonable decisions, not to excuse all mentally ill people from criminal culpability.  This standard emphasises cognitive impairment and the individual’s ability to comprehend the nature and consequences of their actions.

Model Penal Code (MPC) Test:

This test included two elements: The defendant must not be able to understand why their actions are illegal (cognitive incapacity) and unable to change their behaviour to comply with the law (volitional incapacity). [5]


There are several landmark cases that shaped the legal understanding and the application of the insanity as the defence under the legal system. The most famous among all is the McNaughten’s case (1843), which we had already been discussed above.

Durham v. United States (1954)[6]: This case derives the concept of Durham rule, which introduced the broader prospective of legal insanity. It was held that the accused was not criminally responsible for his act if it was the product of mental disease or any defect. This expanded the scope beyond the McNaughten Rule.

Ford v. Wainwright (1986)[7]: This case addressed the issue of executing an insane person. The supreme court ruled that it is unconstitutional to execute someone who is insane, as it violates the 8th Amendment’s prohibition against cruel and unusual punishment.

Andrea Yates case (2006): Andrea Yates was suffering from severe postpartum depression, by drowning her five children in her neighbour’s bathtub. This case highlights the sparkling debate in applying insanity as a legal defence.


      The defence of insanity with a lot of positive factors was also criticised by many jurists. There are several reasons for its criticism, as follows:

Subjectivity and ambiguity: Critics argued that the concept of insanity is highly subjective in nature and relies mostly on expert opinion, which makes it more susceptible to manipulation. The term insanity, although emphasizing on cognitive incapacity still criticised on being ambiguous and open to interpretation[8].

Malingering and Manipulation: There might be a scenario in which the accused might represent himself under false mental illness to escape from liability. The fear of malingering creates skepticism regarding the validity of the insanity claim. High-profile cases in which convicts are acquitted on the grounds of insanity may exacerbate public mistrust of the justice system.

The stigma attached to mental illness: Because the insanity defence links mental disease to criminal activity, it may exacerbate the stigma associated with mental illness. There are worries that associating mental illness with criminal activity could reinforce unfavourable preconceptions and impede initiatives aimed at lessening the stigma associated with mental health disorders.

Unpredictability in Application:  There may be impressions of injustice and inconsistent treatment of the insanity as a defence due to the number of variations in how it is applied in different situations and countries.

Some contend that the standards for insanity are not uniformly applied and that circumstances like the defendant’s socioeconomic background or the quality of their legal counsel may have an impact on the verdict.

Concerns for Public Safety:  Public safety is also a source of concern for critics, particularly when people deemed innocent due to insanity are later allowed to return to society. There can be fears that these people could endanger society.

Reform and Other Methodologies:  Alternative approaches to addressing mental health concerns within the criminal justice system, such as mental health courts or diversion programmes, are frequently at the centre of reform calls.

Even while insanity as a defence is still a well-established legal theory in many jurisdictions, continuous arguments and discussions show how difficult it is to strike a balance between the rights of those with mental illnesses, public safety, and justice. Legal frameworks could keep changing in reaction to these disputes and complaints.


The term ‘insanity’ in legal terms refers to the mental state of the individual which may excuse an individual from the criminal responsibility. However, according to psychology, it is not the same. The mental health professional uses various diagnostic criteria to ascertain the mental health of the person.

Mental disorder: Numerous mental illnesses are recognised by psychology, each with its own set of symptoms, causes, and interventions. Mental illnesses that might affect a person’s ability to operate emotionally and cognitively include major depressive disorder and bipolar disorder. Mental illnesses that affect perception, reasoning, or memory are frequently seen in legal contexts as affecting an individual’s cognitive functioning and being important in determining criminal liability. Certain mental health disorders have a tendency to impair mental capacity, which in turn affects a person’s capability to understand the nature and consequences of their actions or to modify their behaviour to fit social norms. This could involve delving into a legal debate to determine whether each party’s claim is valid or invalid. Mental health practitioners evaluate a patient’s potential for recovery and treatment in clinical settings. This could be important when it comes to legal issues, particularly in situations where therapy may be able to enhance or restore mental health. In both clinical and legal situations, psychologists and psychiatrists are essential in conducting assessments, offering professional judgements, and adding to a thorough understanding of a person’s mental condition.


Understanding the intricacy of the relationship between mental health and the criminal justice system is essential to meet the requirement of mentally ill accused. Therefore, alternative methods are developed in order to provide better care and protection to mentally ill offenders.

A specialised court system was inaugurated known as mental health courts to tackle the issues involving people who have mental disease and get involved in any criminal activity. The aim of these courts is to steer people to community-based mental health treatment and provide support services.

Crisis Intervention Team (CIT) programmes [9]organise programs for law enforcement personnel to identify and assist people going through any mental health crisis. These officers were trained with de-escalation techniques and are often connected with the mental health professionals, in order to guarantee proper care and intervention.

Forensic Assertive Community Treatment (FACT)[10], specialised team of mental health assist the people in both mental health and legal concern.

In order to lower the risk of recidivism, the programme of probation and parole are specifically designed for mentally ill person to provide them assistance, monitoring, team adherence requirement and other support services.

These alternative strategies aim to strike a balance between the need for proper mental health care and public safety concerns, acknowledging that people with mental illnesses may benefit more from assistance and therapy than from more conventional punitive tactics. Policymakers, law enforcement, legal experts, and mental health specialists must work together to implement comprehensive, community-based measures.   


The insanity as a defence continues to be a topic of discussion in the field of law and mental health.  A number of discussions were made on its validity. Here are some of the observations regarding the aforesaid topic and the possible advancement that we can make from our end to insanity as a defence in the future. The proper legal criteria for defining insanity is a topic of continuous discussion. Many argued for a more comprehensive strategy that considers not only moral responsibility, volitional incapacity, and cognitive incapacity. The Model Penal Code (MPC) test might be re-examined and used in more jurisdictions because it combines cognitive and volitional components. Also, the advancement in neuroscience provides greater edge to understand the relationship between functioning of brain and criminal behaviour. By integrating neuroscientific evidence to the defence of insanity will corroborate more in ascertaining the mental state of the accused ant the time of the commission of the offence.

The specialized court for the individual suffering mental illnesses may become more prevalent and enhance the credibility and veracity to the person accused of certain offence, for which he is not conscious. These programs aim at providing alternative traditional criminal justice procedures that will offer support services and assistance to the addressed underlying mentally ill person. Public stigma and public perception also play crucial role, to reduce stigma and create awareness among the people about mental health may impact how society actually treats the person who make the plea of insanity as a defence from the criminal liability. Thus, this would increase the legal standard and decisions.

Ethical consideration are also surrounded in the defence of insanity, that include the question of justice, fairness and individual rights, which always need to be forefront in any legal proceedings. The court has to keep in mind, to maintain the balancing between protection of society and respecting the moral and ethical rights of individual with mental illness. None of the rights get infringed.

As the understanding of mental health and the legal landscape evolves, ongoing debates and potential future developments in the insanity defence will be shaped by a combination of legal, scientific, societal, and ethical considerations.


  1. The origin and development of the ‘Wild beast’ concept of mental illness and its relation to theories of criminal responsibility.

  1. Insanity as an exception to criminal liability.

  1. Crisis Intervention Team

  1. Criminal Malingering: Defendant who fake mental illness

  1. Treatment Alternative to Incarnation for individuals suffering from mental conditions

  1. Forensic Assertive Community treatment (FACT)

[1] Anthony M. Platt, The origin and development of the ‘Wild beast’ concept of mental illness and its relation to theories of criminal responsibility, Vol. 1 Issue 1, Social justice/Global option JSTOR

[2] 1760 (Walker 1968:63)

[3] Mayukhroy, Difference between legal and medical insanity, Legal services India E-Journal

[4] (1812) 1 Collinson Lunacy 673

[5] Gray Watson, The Insanity defence, Vol. 14, Law explorer, 07 Nov, 2016

[6]  214 F.2d 862 (D.C. Cir. 1954)

[7] 477 U.S. 399 (1986)

[8] T.V. Asokan, The insanity defence : Related issue,  Indian Journal of Psychiatry, 2016 Dec

[9] Laura Usher, Amy Watson, Ron Brono, Crisis Intervention Treatment Programme, 244-04, 2019 Aug

[10] Forensic Assertive Community Treatment (FACT),

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