Necessity as a General Exception: Section 19 BNS and the Doctrine of Choice of Evils

A ship's captain, faced with a collision he cannot avoid, must choose whether to hit a boat with twenty passengers or a boat with a hundred. A surgeon, faced with an impossible obstetric emergency, must choose whether to save the mother or the child. A pilot, faced with a certain crash, must choose whether to come down on a crowded market or an empty field. In each case, the actor knows the harm he is about to cause, but he causes it to avoid a greater harm. Should the criminal law treat him as an offender? Section 19 of the Bharatiya Nyaya Sanhita, 2023, answers no. This module walks through the doctrine of necessity, its narrow scope, and the leading Indian and English authorities.

1. Meaning and Concept

Necessity in criminal law

Necessity, in the criminal law sense, is the doctrine that a person who causes a lesser harm to prevent a greater one is not criminally liable, provided he acted in good faith and without criminal intention. The classical formulation is that of a choice of evils: the actor was faced with a situation in which harm was inevitable, and he chose the course that resulted in the lesser harm. The doctrine is narrow. It does not permit the sacrifice of innocent life to save one's own, and it does not extend to acts that would be criminal even in the absence of the necessity.

The choice of evils doctrine

Necessitas non habet legem

Necessitas non habet legem.

Necessity knows no law. The Latin maxim, drawn from Roman law and elaborated by the medieval canonists, expresses the doctrinal position that necessity can suspend the ordinary operation of a legal rule. The maxim is a rhetorical shorthand, not a literal proposition: modern criminal law imposes strict limits on the defence, and necessity does not, in fact, override every rule. But the maxim captures the intuition that a person acting under genuine necessity has a moral claim on the law's forbearance.

2. Historical Origin

Roman and canon law

Roman law recognised necessity as an exception to certain rules, particularly in cases of famine, natural disaster, and shipwreck. The maxim necessitas non habet legem was in circulation by the classical period. The canon law of the medieval church absorbed the doctrine and connected it to the moral requirement of proportionality: the actor was excused only where the harm avoided was greater than the harm caused.

English common law

English common law recognised necessity in a narrow form. Bracton, in the thirteenth century, treated it as excluding criminal responsibility in specified circumstances. Coke and Blackstone confirmed the position but confined it strictly. The English tradition has been more cautious about the doctrine than the civil law jurisdictions, and modern English law recognises necessity only in very narrow circumstances.

R. v. Dudley and Stephens (1884)

Reception into the Indian Penal Code

Macaulay codified the doctrine in Section 81 IPC, drawing on both the civilian tradition of necessity and the English restraint. The Indian section is textually broader than the English common law defence of that era, but it retains the fundamental limit implicit in Dudley and Stephens: necessity does not excuse a person who takes life for his own preservation. The Bharatiya Nyaya Sanhita retains the section, unchanged in substance, as Section 19.

3. Statutory Provision

Section 19 BNS (formerly Section 81 IPC)

Text and structural analysis

The section has four elements. All must be satisfied for the defence to succeed.

• The act must have been done with knowledge that it was likely to cause harm.
• There must be no criminal intention to cause harm.
• The act must have been done in good faith (Section 2(11) BNS: with due care and attention).
• The purpose of the act must have been to prevent or avoid other harm to person or property.

The Explanation adds a crucial qualification: whether the harm avoided justified the harm caused is a question of fact, and it is decided by the court after the event. The actor's assessment at the time is not conclusive.

4. Ingredients of Section 19

Knowledge that the act is likely to cause harm

The section applies where the actor knows that his act is likely to cause harm. This distinguishes necessity from accident under Section 18 BNS, which requires the absence of criminal intention or knowledge. Under necessity, the actor knows the likely consequence but proceeds because a greater harm awaits if he does not.

Absence of criminal intention

The actor must have no criminal intention. He knows the harm his act will cause, but he does not intend that harm. His intention is to avoid the greater harm. The distinction is subtle but important: intention is what one aims at; knowledge is what one is aware will follow. In necessity, the intention is directed at avoiding the greater harm, and the lesser harm is a foreseen but unwelcome consequence.

In good faith

Section 2(11) BNS applies. Good faith requires due care and attention. The actor must have taken reasonable steps to assess the situation, to choose the course of least harm, and to minimise the harm he inevitably causes. A reckless or careless choice, even if it turns out to have been the lesser evil, does not qualify.

For the purpose of preventing or avoiding other harm

The purpose must be to prevent or avoid another harm to person or property. Purely self serving motives do not qualify. The other harm must be genuine, imminent, and greater than the harm the actor causes. Where the actor's purpose is mixed (partly to avoid harm, partly to gain personal advantage), the section applies only if the necessity purpose is the operative one.

5. The Proportionality Requirement

Harm caused must be less than harm avoided

The Explanation to Section 19 makes the proportionality requirement explicit: whether the harm to be avoided was of such a nature and so imminent as to justify or excuse the risk of the act is a question of fact. The court, applying an objective standard, decides whether the choice made was reasonable. Where the harm caused is greater than the harm avoided, the defence fails. Where the two are equivalent, the defence generally succeeds only if the harm was truly unavoidable.

The judgment of the court after the fact

The proportionality assessment is made ex post, that is, after the event, by the court. The actor's assessment at the time is relevant but not decisive. The court examines the situation as it actually was, and asks whether a reasonable person in the position of the actor would have chosen the same course. This is a form of hindsight bias check on the doctrine: the actor cannot claim necessity simply because he believed he was choosing the lesser evil. He must have been choosing the lesser evil in fact.

6. Illustrations under the Section

The two illustrations capture the classical situations: the choice between two boats (proportionality of the choice), and the destruction of property to prevent a greater loss (the firebreak). Both are decided by the ex post proportionality assessment.

7. Distinction from Related Doctrines

Necessity vs duress (Section 32)

Necessity vs private defence (Sections 34 to 44)

Private defence is a right; necessity is an excuse. Private defence is directed against an unlawful aggressor. Necessity may involve causing harm to an innocent third party. Private defence extends, in specified circumstances, to voluntarily causing death. Necessity does not extend to taking innocent life to preserve one's own. Where the aggressor's conduct triggers the defensive response, private defence is the operative provision. Where a natural situation forces the choice of evils, necessity is.

Necessity vs accident (Section 18)

Accident requires the absence of criminal intention and knowledge. The actor did not know the harm was likely. Necessity, by contrast, applies where the actor knew the likely harm but proceeded to avoid greater harm. The two doctrines address different mental states. An accident is unforeseen; a necessity is foreseen but chosen.

8. Judicial Elaboration

R. v. Dudley and Stephens: necessity no defence to murder

Discussed above. The foundational modern English case, and the source of the rule that necessity does not extend to taking an innocent life to preserve one's own. The Indian position under Section 19 BNS is broadly consistent.

United States v. Holmes

Re A (Conjoined Twins): a modern refinement

Bishambhar v. Roomal

Gopal Naidu v. Emperor

9. The Limits of Necessity

• Necessity does not extend to killing an innocent to save oneself. R. v. Dudley and Stephens.
• Necessity does not extend where the actor had a reasonable alternative. If the actor could have avoided all harm by taking a different course, necessity does not apply.
• Necessity does not extend where the actor voluntarily placed himself in the situation. A person who chooses to embark on a dangerous enterprise, knowing the risk, cannot claim necessity when the danger materialises.
• Necessity is not a defence to offences of strict liability under public welfare statutes, unless the statute expressly permits it.
• Necessity requires proof of the actor's good faith. Where the actor acted recklessly, or without proper assessment of the situation, the section does not apply.

10. Consolidated Landmark Judgments

• R. v. Dudley and Stephens, (1884) 14 QBD 273. Necessity no defence to murder. Foundational modern English case.
• United States v. Holmes, 26 F Cas 360 (1842). American approach: necessity may extend to taking life in extreme cases, subject to fair selection.
• Re A (Children) (Conjoined Twins: Surgical Separation), [2000] EWCA Civ 254. Modern refinement of necessity in extreme medical cases. Three requirements laid down.
• Bishambhar v. Roomal, AIR 1951 All 500. Necessity combined with consent to protect community based dispute resolution.
• Gopal Naidu v. Emperor, (1922) 46 Mad 605. Public order maintenance as necessity within Section 81 IPC.
• Southwark London Borough Council v. Williams, [1971] Ch 734. English case rejecting necessity as a defence to squatting by homeless persons. Lord Denning MR: necessity would open a door which no man could shut.
• R. v. Kitson, (1955) 39 Cr App R 66. Necessity considered in a drunk driving case. Very narrow application.
• R. v. Willer, (1986) 83 Cr App R 225. Duress of circumstances as a form of necessity. Recognised in modern English law.
• R. v. Martin, [1989] 1 All ER 652. Duress of circumstances extended to driving offences. Objective test of necessity applied.
• Yeager Building Corp v. State, (1908) 68 Pa Super 108. American case on necessity in property destruction to prevent conflagration.

Frequently Asked Questions

What is Section 19 BNS?

Section 19 of the Bharatiya Nyaya Sanhita, 2023 (formerly Section 81 IPC), provides that nothing is an offence merely by reason of its being done with the knowledge that it is likely to cause harm, if it be done without any criminal intention to cause harm, and in good faith for the purpose of preventing or avoiding other harm to person or property. It codifies the doctrine of necessity or choice of evils.

Is necessity a defence to murder in India?

No. Following R v Dudley and Stephens (1884) 14 QBD 273, necessity does not extend to taking an innocent life to preserve one's own. The Indian position under Section 19 BNS is broadly consistent. A person cannot invoke necessity to escape a charge of murder based on the killing of an innocent person for his own survival.

What is the difference between necessity and duress?

Necessity (Section 19 BNS) arises from natural circumstance: the actor is faced with a natural danger (fire, flood, shipwreck) and must act to avoid it. Duress (Section 32 BNS) arises from a human threat: another person threatens the actor with instant death if he does not do the act. Necessity has no absolute exclusions in the statute (though the murder limit applies); duress expressly excludes murder and offences against the state punishable with death.

What are the ingredients of Section 19 BNS?

Four ingredients: (i) the act was done with knowledge that it was likely to cause harm; (ii) there was no criminal intention to cause harm; (iii) the act was done in good faith (Section 2(11) BNS: with due care and attention); and (iv) the purpose was to prevent or avoid other harm to person or property. All four must be established.

What is the proportionality requirement under Section 19 BNS?

The Explanation to Section 19 makes proportionality explicit: whether the harm to be avoided was of such a nature and so imminent as to justify the risk of the act is a question of fact, decided by the court after the event. The harm caused must be less than the harm avoided. Where the two are equivalent, the defence generally succeeds only if the harm was truly unavoidable.

What are the classical illustrations of necessity?

The section itself gives two: (i) the captain of a steam vessel who alters course to avoid a boat with twenty passengers and, in doing so, hits a boat with two; (ii) a person who pulls down houses in a great fire to prevent the fire spreading. Both are examples of causing lesser harm in good faith to avoid greater harm.

Related Topics on The Legal Bridge

For a fuller picture, read these companion notes on adjacent doctrines and provisions:

• General Exceptions under the BNS: the wider chapter (Sections 14 to 44) in which Section 19 sits.
• Compulsion by Threats: the parallel doctrine under Section 32 BNS for human threats.
• Right of Private Defence: the related doctrine for defensive responses to unlawful aggression.
• Accident as a General Exception: the excusable defence under Section 18 BNS.