INTRODUCTION
Medical insanity is a well-established exception within criminal jurisprudence, recognised as a legitimate ground of defence under Indian law. It finds statutory expression in Section 22 of the Bharatiya Nyaya Sanhita 2023, which provides that an act is not an offence if, at the time of doing it, the person, by reason of unsoundness of mind, is incapable of knowing the nature of the act or that what they are doing is either wrong or contrary to law. This provision, rooted in the principles laid down in R v McNaughten,[1] reflects the legal system’s recognition that criminal liability must be based on conscious and rational conduct.
The validity of this exception rests on the fundamental premise that, during phases of insanity, a person may be incapable of understanding the nature or consequences of their actions. This aligns with the cardinal maxim actus non facit reum nisi mens sit rea- an act does not constitute guilt unless accompanied by a guilty mind. Complimenting this is the principle furiosi nulla voluntas est, which recognises that a person suffering from unsoundness of mind lacks free will. Together, these doctrines justify why individuals who are genuinely incapable of forming the requisite mens rea are exempted from criminal responsibility.
However, while the importance of this defence cannot be undermined, its potential for misuse cannot be overlooked. The wide medical ambit of insanity, combined with the difficulty of conclusively proving mental incapacity, creates scope for abuse. Indian law attempts to address this concern through procedural safeguards, placing the burden of proof on the accused to bring the case under the ambit of Section 22 of BNS. Despite this, courts are often required to treat cautiously, ensuring that the defence serves its true purpose – protecting those who lack culpability, without becoming a tool to evade justice. Insanity pleas only had a success rate of about 17% in Indian High Courts from 1.1.2007 to 31.08.17.[2]
HISTORY AND EVOLUTION
The insanity defence in criminal law is primarily based on the landmark case of R v McNaughten. It reflects the fundamental principle of actus non facit reum nisi mens sit rea.
In 1843, Daniel McNaughten shot Edward Drummond, mistaking him for the British Prime Minister. McNaughten was charged with murder. However, during the trial, the defence argued that he was not of sound mind at the time of the act and was suffering from severe delusions. Medical experts testified the same and stated that the condition impaired his understanding of reality.
The House of Lords found McNaughten not guilty by reason of insanity, which led to the formulation of the famous McNaughten Rules. It was established that every person is presumed sane unless proven otherwise. To successfully claim insanity, it must be shown that at the time of committing the act, the accused was suffering from a defect of reason caused by a disease of the mind, such that he either did not understand the nature and quality of the act or did not know that it was wrong or contrary to law.
These principles form the basis of the insanity defence in many jurisdictions, including India. Under Section 22 of the BNS, a person is exempt from criminal liability if, due to unsoundness of mind, they are incapable of understanding the nature of their act or that it is wrong. The McNaughten Rule continues to play a crucial role in balancing criminal responsibility with mental incapacity in modern law.
The defence of insanity has been shaped through various judicial decisions, each reinforcing the narrow scope of legal insanity as distinct from mere medical abnormality. It is now settled law that establishing the presence of mental illness just before and after the crime doesn’t suffice; the substantiality of the impairment at the time of the act must also be established.[3] The judiciary later articulated principles governing the burden of proof in insanity cases through a structured framework.[4]
- The prosecution must prove beyond a reasonable doubt that the accused committed the offence with the requisite mens rea.
- There is a rebuttable presumption that the accused was not insane at the time of the crime. The accused can rebut this with evidence before the court on the preponderance of the probabilities.
- If the accused cannot conclusively establish insanity, the evidence may still raise a reasonable doubt about the existence of mens rea, and if so, the benefit must go to the accused.
Indian judiciary, especially the Supreme Court, has time and again reiterated the fact that mental illness is not automatically exempt from criminal liability, and that there is a clear distinction between mental insanity and legal insanity.[5]
It is also important to note that Indian Courts place a considerable reliance on psychiatric and expert medical evidence while adjudicating pleas of insanity, recognising its importance in assessing the mental condition of the accused. However, such evidence is not treated as conclusive and must align with the strict legal requirements of Section 22 of BNS. Empirical data further highlight the narrow scope of this defence in practice. A study[6] examining insanity pleas across 13 Indian High Courts between 2007 and 2017 revealed that out of 102 cases, courts convicted the accused in 76 instances, while the defence of insanity was accepted only in 18 cases (17.65%). These figures clearly demonstrate the judiciary’s cautious and restrictive approach while dealing with insanity pleas.
CRITICAL ANALYSIS
A critical examination of the McNaughten Rule reveals significant limitations when applied in modern criminal law. Although courts place considerable reliance on psychiatric and medical expert testimony, accurately determining the mental condition of an accused at the precise moment of committing the offence remains inherently difficult. Mental illness is not static; it fluctuates, often unpredictably, making retrospective assessment highly uncertain and dependent on inference rather than certainty.
The rule itself adopts a narrow and somewhat rigid standard by focusing on whether the accused lacked the capacity to understand the nature of the act or to know that it was wrong. This formulation, while foundational, appears overly simplistic and vague when tested against contemporary psychiatric knowledge. Mental illnesses manifest in diverse forms and degrees, such as Schizophrenia, Bipolar Disorder, Paranoid Delusion, and Dissociative Disorders, each involving varying levels of cognitive impairment, distorted perception, or episodic loss of control. The McNaughten framework fails to adequately capture these nuances, as it reduces the inquiry to a binary assessment of knowledge and intention.
Another critical limitation, as repeatedly observed by the Supreme Court, is that evidence of insanity before or after the commission of the crime does not automatically establish insanity at the time of the act. This creates a significant evidentiary challenge. Since direct proof of the accused’s mental state at the exact moment of the offence is rarely available, the burden placed upon the accused becomes disproportionately heavy. They must reconstruct a past mental condition through circumstantial and expert evidence, often falling short of the strict legal threshold.
In the context of modern criminal jurisprudence, continued reliance on a 19th-century doctrine like the McNaughten Rule raises concerns about its adequacy in delivering substantive justice. While the rule aims to balance individual incapacity with societal protection, its rigid application may, in many cases, fail to accommodate the complexities of mental health, thereby limiting its effectiveness in achieving true justice.
CONCLUSION
The defence of insanity highlights a tension between legal principle and practical reality. Although it is formally recognised under Section 22 of the Bharatiya Nyaya Sanhita, the burden of proving unsoundness of mind at the exact time of the offence remains extremely high, making successful reliance on the defence rare.
At the same time, judicial caution is shaped by the risk of misuse. Incidents such as the Pune Porsche car crash of 2024 illustrate the concern that accused persons may attempt to take advantage of legal exceptions by portraying themselves as mentally unsound to escape liability. Where it appears that an accused is aware of such defences and tries to falsely present symptoms of insanity, courts are compelled to scrutinise the plea even more strictly. This reinforces a stricter evidentiary standard, particularly in serious offences.
Thus, the law operates within a delicate balance; on one hand, it must safeguard genuinely incapacitated individuals, and on the other, it must prevent manipulation of the system. However, this heightened suspicion and rigorous burden often make the defence difficult to establish in practice. As a result, while the insanity defence continues to exist in law, its accessibility is significantly limited, risking its transformation into a largely theoretical safeguard rather than an effective remedy in real cases.
Authors: Dishamoni Deka & Himonjyoti Parasar (University Law College, Gauhati University)
References:
[1] R v McNaughten (1843) 10 CL & Fin 200; 8 ER 718
[2] Parthasarathy Ramamurthy, Vijay Chathoth, Pradeep Thilakan, “How does India Decide Insanity Pleas? A Review of high Court Judgements in the Past Decade”, Indian Journal of Psychological Medicine, (2021), 41(2): 150
[3] Queen Empress v Kader Nasyer Shah (1896) ILR 23CAL604
[4] Dahyabhai Chhanganbhai Thakker v State of Gujarat (1964) AIR 1563
[5] Surendra Mishra v State of Jharkhand AIR 2011 SC 627
[6] Parthasarathy Ramamurthy, Vijay Chathoth, Pradeep Thilakan, “How does India Decide Insanity Pleas? A Review of high Court Judgements in the Past Decade”, Indian Journal of Psychological Medicine, (2021), 41(2): 150-151
