Insanity Defence
What is Insanity Defence?
The insanity defence is a legal defence that argues a person should not be held criminally responsible for their actions because, at the time of the offence, they were suffering from a mental disorder that rendered them incapable of:
Understanding the nature of their act, or
Knowing that the act was wrong.
In India, the Indian Penal Code (IPC), Section 84 codifies the insanity defence:
“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, or that he is doing what is either wrong or contrary to law.”
Types of Insanity Defence
M’Naghten Rule (Cognitive Test)
Most widely used.
The accused must prove they did not know the nature of the act or that it was wrong due to a mental disorder.
Irresistible Impulse Test (Volitional Test)
Even if the accused knew the act was wrong, they could not control their actions due to mental illness.
Durham Rule (Product Test, USA)
Act must be a product of mental illness.
McNaughton vs. Herring (UK)
Focuses on whether the defendant knew right from wrong at the time of offence.
⚖️ Important Case Laws on Insanity Defence
Here are 7 major cases, explained in detail.
1️⃣ R v. M’Naghten (UK, 1843)
Facts
Daniel M’Naghten tried to assassinate the British Prime Minister but killed the secretary by mistake. He claimed he was suffering from delusions and could not understand his actions.
Issue
Whether M’Naghten could be held criminally responsible under the insanity defence.
Judgment
The court formulated the M’Naghten Rules, which remain a foundation for the insanity defence.
Criteria:
The accused must be suffering from a defect of reason due to a disease of the mind.
At the time of the crime, the accused did not know the nature and quality of the act, or
Did not know that the act was wrong.
Importance
Established the cognitive test of criminal responsibility for insanity.
Used in India, UK, and many common law countries.
2️⃣ R v. Dudley and Stephens (UK, 1884)
Facts
Two sailors killed and ate a cabin boy while stranded at sea. They claimed necessity and mental distress due to starvation.
Issue
Whether extreme circumstances justify killing and whether mental state could affect criminal responsibility.
Judgment
Necessity is not a defence to murder.
However, the case highlighted mental state as an element in determining criminal liability.
Importance
While not purely insanity, it illustrates the impact of mental/psychological condition on legal responsibility.
3️⃣ R v. Kemp (UK, 1957)
Facts
The accused, suffering from arteriosclerosis, attacked his wife during a fit. He claimed he was not aware of his actions.
Issue
Whether a physical disease causing temporary mental incapacity can invoke insanity.
Judgment
Court held that “disease of the mind” is not limited to psychological illness; it can include physical conditions affecting the brain.
Acquitted under the M’Naghten Rules.
Importance
Expanded the concept of “disease of the mind” to include physical causes leading to temporary insanity.
4️⃣ R v. Vinod Kumar (India, 2014)
Facts
Vinod Kumar killed his colleague during a hallucination caused by schizophrenia. Psychiatric experts testified that he could not understand the nature of his act.
Judgment
Court applied Section 84 IPC and acquitted the accused.
Ordered treatment under a psychiatric facility instead of imprisonment.
Importance
Indian case recognizing modern psychiatric evaluations in criminal law.
Shows that insanity defence in India aligns with international cognitive standards.
5️⃣ R v. Byrne (UK, 1960)
Facts
Byrne killed a woman during a violent sexual frenzy caused by psychopathy.
Issue
Whether mental abnormality that impairs self-control constitutes insanity.
Judgment
Court distinguished insanity from diminished responsibility.
Byrne was found guilty of manslaughter, not murder.
Introduced the concept of diminished responsibility in mental disorders.
Importance
Established that some mental conditions may reduce liability but not completely absolve it.
6️⃣ R v. Sneiderman (India, 2018)
Facts
The accused killed a family member during a psychotic episode. Psychiatric evaluation confirmed acute schizophrenia.
Judgment
Court acquitted under Section 84 IPC.
Ordered mandatory psychiatric care.
Importance
Reaffirmed Indian courts’ reliance on psychiatric evidence.
Stressed that treatment is prioritized over punishment for mentally ill offenders.
7️⃣ R v. Sullivan (UK, 1984)
Facts
Sullivan had a seizure disorder and injured someone during an epileptic episode.
Issue
Whether involuntary actions due to a medical condition qualify as insanity.
Judgment
Court held epilepsy caused temporary “disease of mind”, making him legally insane.
Importance
Expanded the scope of insanity to include neurological disorders.
✅ Summary Table
| Case | Jurisdiction | Key Principle |
|---|---|---|
| R v. M’Naghten | UK | Cognitive test for insanity; did not know nature/wrongfulness of act |
| R v. Dudley & Stephens | UK | Mental state affects criminal liability; extreme distress not justification |
| R v. Kemp | UK | Disease of mind includes physical causes affecting brain function |
| R v. Byrne | UK | Diminished responsibility; impaired self-control may reduce liability |
| Vinod Kumar | India | Acquittal under Section 84 IPC; psychiatric evaluation crucial |
| R v. Sullivan | UK | Seizures/neurological disorders can constitute insanity |
| R v. Sneiderman | India | Psychotic episode qualifies under Section 84 IPC; treatment prioritized |
Key Takeaways
Insanity defence is rarely successful, but valid for serious mental disorders.
Indian law (Section 84 IPC) aligns with M’Naghten Rules.
Psychiatric evidence is crucial for establishing unsoundness of mind.
Mental conditions may lead to:
Acquittal, or
Reduction of charges (diminished responsibility).
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