Insanity: Medical Jurisprudence and Criminal Responsibility
Introduction
In everyday language, the term “insanity” is often used loosely to describe unusual, irrational, or extreme behaviour. In medicine and law, however, the concept has a more specific significance. Modern medicine generally avoids “insanity” as a diagnostic term and instead uses precise concepts such as mental disorder, mental illness, psychopathology, and neurocognitive disorder. The distinction between medical and legal concepts is particularly important in medical jurisprudence because a person may have a diagnosed mental disorder without necessarily satisfying the legal test for criminal responsibility.
From “Insanity” to Modern Psychiatry
Historically, many different forms of abnormal behaviour were grouped under broad and stigmatising labels such as “madness” or “insanity”. Modern psychiatry recognises that mental disorders are distinct conditions with different causes, symptoms, courses, and treatments. Examples include:
- Schizophrenia: A severe mental disorder that may involve disturbances in perception, thinking, beliefs, behaviour, and the individual’s experience of reality.
- Bipolar Disorder: A disorder characterised by episodes of significant changes in mood, energy, activity, and functioning, including manic or hypomanic and depressive episodes.
- Dementia/ Neurocognitive Disorders: Conditions involving acquired impairment in cognitive functions such as memory, reasoning, language, and judgement.
Thus, modern mental health practice focuses on diagnosis, symptoms, functional impairment, treatment, and rehabilitation, rather than the outdated binary classification of a person as “sane” or “insane”.
The Legal Concept: The Insanity Defence
The insanity defence is a legal doctrine concerning criminal responsibility. Its underlying principle is that a person should not be held criminally responsible in the ordinary manner when, because of a qualifying mental condition, they lacked the legally required capacity to understand the nature or wrongfulness of their conduct at the relevant time.
A crucial distinction must therefore be made between medical insanity and legal insanity. Medical insanity concerns the existence and nature of a mental disorder as assessed by mental-health professionals. Legal insanity, by contrast, is a legal conclusion determined by the court according to the applicable statutory test. A medical diagnosis alone does not automatically establish legal insanity.
The Law in India
In India, the relevant provision is Section 22 of the Bharatiya Nyaya Sanhita, 2023 (BNS), which corresponds substantially to Section 84 of the former Indian Penal Code, 1860. The provision is based on the principle that an act is not criminal when, at the time of doing it, the person, because of unsoundness of mind, was incapable of knowing the nature of the act or that what they were doing was wrong or contrary to law.
The essential point is that the accused’s mental condition at the time of the act is critical. A past history of mental illness, previous psychiatric treatment, or the presence of a diagnosed disorder does not by itself establish the defence. The evidence must demonstrate the legally relevant incapacity at the time of the offence.
Medical Insanity and Legal Insanity
Medical Insanity
‘Medical insanity’ refers to a clinically recognised mental disorder diagnosed or assessed by qualified mental-health professionals.
Legal Insanity
Legal insanity refers to the inability to satisfy the applicable legal standard of criminal responsibility because of the person’s mental condition at the relevant time.
Consequently, every medically ill person is not legally insane, and the existence of mental illness does not automatically exempt a person from criminal responsibility.
Mental Fitness to Stand Trial
The law also distinguishes between a person’s mental condition at the time of the offence and their mental capacity during criminal proceedings. A person may have been mentally capable when the alleged offence occurred but later become incapable of understanding the proceedings or effectively participating in their defence.
Where the law permits and the required conditions are established, criminal proceedings may therefore be postponed or otherwise dealt with according to the applicable procedural safeguards until the accused is sufficiently capable of understanding the proceedings and participating in their defence. Appropriate psychiatric assessment and treatment may be ordered where necessary.
Comparative Perspective
Different legal systems apply different standards to determine criminal responsibility in cases involving mental disorder:
- United Kingdom: The traditional M’Naghten Rules ask whether, because of a “disease of the mind”, the accused was unable to understand the nature and quality of the act or, if they understood its nature and quality, were unable to understand that the act was “wrong”.
- United States: Different jurisdictions apply different tests. These may include the M’Naghten test, the Model Penal Code substantial-capacity test, or, in some jurisdictions, doctrines relating to an irresistible impulse. The precise rules vary by state.
- Civil-law jurisdictions: Countries such as Germany and France generally distinguish between complete lack of criminal responsibility and situations involving substantially diminished responsibility, which may affect punishment and lead to therapeutic or protective measures.
Therefore, there is no single universal legal definition of insanity; the applicable test depends upon the jurisdiction and governing law.
Insanity Defence and Human Rights
The modern approach to mental disorder in criminal justice is increasingly informed by human dignity, equality, humane treatment, public safety, and rehabilitation. Persons with severe mental disorders should not be treated merely as offenders when their mental condition fundamentally affects their capacity for criminal responsibility.
The insanity defence is therefore not intended simply as a means of escaping punishment. It reflects the principle that criminal responsibility must take account of the individual’s mental capacity as recognised by law. At the same time, public safety remains an important consideration, and courts may impose appropriate protective, supervisory, or treatment-orientated measures in accordance with law.
Temporary Insanity
The expression “temporary insanity” is commonly used to describe a claimed period of severe mental disturbance existing only around the time of an offence. However, its legal recognition varies between jurisdictions. In India, the central question is not whether a person can be labelled “temporarily insane”, but whether the statutory requirements concerning unsoundness of mind and the accused’s mental capacity at the time of the act are established.
Therefore, temporary emotional disturbance, anger, intoxication, stress, or impulsive behaviour should not automatically be equated with legal insanity.
Recognising Warning Signs of Mental Health Problems
Mental health difficulties can present differently in different individuals. Warning signs may include:
In Adults
- Persistent sadness, anxiety, or irritability
- Confused or markedly disorganised thinking
- Unusual beliefs or perceptions
- Social withdrawal or loss of interest in usual activities
- Significant changes in sleep or appetite
- Difficulty functioning at work or in daily life
- Harmful or problematic substance use
In Children and Adolescents
- Sudden decline in academic performance
- School avoidance or frequent absenteeism
- Persistent withdrawal from family or friends
- Frequent or severe emotional outbursts
- Marked changes in behaviour or personality
- Persistent fears, anxiety, or nightmares
- Significant changes in eating behaviour or concern about body weight
- Hyperactivity, impulsivity, or persistent behavioural difficulties
These signs do not by themselves establish a psychiatric diagnosis. Professional assessment is necessary to determine their cause and significance.
Common Mental-Health Disorders
Modern psychiatric classifications recognise a wide range of mental and behavioural disorders. Some commonly encountered conditions include:
- Generalised Anxiety Disorder (GAD): Persistent and excessive anxiety and worry about multiple areas of life, often accompanied by symptoms such as restlessness, fatigue, irritability, or difficulty concentrating.
- Major Depressive Disorder (MDD): A condition involving persistent depressed mood or loss of interest or pleasure, together with associated cognitive, emotional, and physical symptoms that significantly affect functioning.
- Obsessive-Compulsive Disorder (OCD): Characterised by recurrent intrusive thoughts, urges, or images and/or repetitive behaviours or mental acts performed in response to them.
- Post-Traumatic Stress Disorder (PTSD): May develop following exposure to actual or threatened death, serious injury, or sexual violence and can involve intrusive memories, avoidance, negative changes in mood and cognition, and heightened arousal.
Case Laws
Mahesh Kumar Verma v. State of Chhattisgarh
In Mahesh Kumar Verma v. State of Chhattisgarh (Criminal Appeal No. 1229 of 2024, decided on July 31, 2025), the High Court of Chhattisgarh at Bilaspur reaffirmed that establishing the defense of legal insanity under Section 84 IPC (now Section 22 BNS) requires evaluating the totality of circumstances—specifically the accused’s conduct prior to, during, and immediately following the incident, alongside the lack of motive and available medical evidence. Reaffirming settled jurisprudence, the Division Bench consisting of Chief Justice Ramesh Sinha and Justice Bibhu Datta Guru emphasized that medical insanity alone does not confer exemption from criminal liability; rather, the decisive test is whether the accused suffered from a disease of the mind that incapacitated them from knowing the nature of the act or that it was wrong or contrary to law at the exact moment the offense was committed.
Bapu @ Gajraj Singh v. State of Rajasthan
In Bapu @ Gajraj Singh v. State of Rajasthan (2007) 8 SCC 66, the Supreme Court unequivocally demarcated the boundary between medical and legal insanity, holding that every mental disorder does not automatically grant immunity under Section 84 IPC (now Section 22 BNS). The Court emphasised that judicial concern lies solely with legal insanity, where the decisive standard is whether, at the exact moment of committing the offence, the accused suffered from such a severe defect of reason from unsoundness of mind that they were rendered incapable of understanding the nature and quality of the act or realising that it was either wrong or contrary to law.
Surendra Mishra v. State of Jharkhand
In this landmark ruling of Surendra Mishra v. State of Jharkhand, (2011) 11 SCC 495, the Supreme Court reaffirmed that an accused seeking exoneration under Section 84 IPC (now Section 22 BNS) must establish legal insanity, not merely medical insanity. The Court emphasised that every person suffering from mental illness does not automatically enjoy immunity; the crucial test is whether the unsoundness of mind incapacitated the accused from knowing the nature of the act or that it was wrong or contrary to law at the time of its commission.
Clarifying the evidentiary threshold, the Court held that while the burden of proving legal insanity rests on the accused under Section 105 of the Evidence Act (now Section 108 BSA), it is satisfied on a preponderance of probabilities through the totality of circumstances—including the accused’s conduct before, during, and after the incident. On evaluating the facts, including the accused’s subsequent conduct, the Court found the plea of insanity unsubstantiated and upheld the conviction.
Dahyabhai Chhaganbhai Thakkar v. State of Gujarat
In Dahyabhai Chhaganbhai Thakkar v. State of Gujarat (AIR 1964 SC 1563), the Supreme Court established the locus classicus on the burden of proof regarding legal insanity under Section 84 IPC (now Section 22 BNS), holding that while the prosecution must prove the accused’s guilt beyond reasonable doubt, the accused’s burden under Section 105 of the Evidence Act (now Section 108 BSA) is far lighter and satisfied on a preponderance of probabilities. The Court clarified that the accused can discharge this burden through medical, oral, or circumstantial evidence of conduct before, during, and after the event; if such evidence creates a reasonable doubt in the mind of the Court regarding the accused’s capacity to know the nature or wrongfulness of the act at the precise time of its commission, the benefit of that doubt must go to the accused.
Conclusion
Mental health should not be understood as a simple division between “sane” and “insane”. Modern medicine recognises a broad spectrum of mental disorders, while law applies specific standards to determine questions of criminal responsibility and fitness to participate in legal proceedings. In medical jurisprudence, the distinction between medical diagnosis and legal insanity is fundamental. A mental disorder may be clinically significant without satisfying the legal test for non-responsibility. The modern approach therefore seeks to balance justice, individual rights, public safety, treatment, dignity, and rehabilitation, while reducing stigma and encouraging timely professional care.
