The right to private defence, enshrined in Sections 96 to 106 of the Indian Penal Code (IPC), 1860, is a fundamental and valuable right that allows an individual to protect their own body and property, or the body and property of another person, against an impending unlawful attack. It is a natural right of self-preservation, recognized by law, to repel an aggression that cannot be prevented otherwise.

However, this right is not absolute and is subject to strict limitations, the most crucial being that it must be exercised reasonably and proportionately. The law does not permit an individual to take the law into their own hands and inflict more harm than is necessary to avert the danger. The principle of reasonableness dictates that:

1. Imminent Threat: The danger must be real and imminent, not merely a remote possibility. There must be no time to have recourse to the protection of public authorities.
2. Proportionality: The force used in self-defence must be proportionate to the harm apprehended. One cannot inflict grievous hurt or death for a minor assault or a petty theft. The harm caused must not exceed the harm necessary to repel the attack.
3. Necessity: The act of private defence must be necessary to avert the danger. If the danger has passed, or if the aggressor has retreated, the right ceases.
4. No Right Against Innocent Act: There is no right of private defence against an act which is not itself an offence (e.g., an act of a child under seven years, or a person of unsound mind).

Examples:

• Defence of Person: If 'A' attacks 'B' with a stick, 'B' is justified in using a stick of similar force to defend himself. However, if 'A' merely pushes 'B', 'B' would not be justified in stabbing 'A'. The force used must be commensurate with the threat. In Vishwanath v. State of U.P., the Supreme Court held that if a person is attacked by a knife, he is not expected to weigh the exact amount of force to be used, but the force must not be excessive. If a person is attacked by a mob, he may use force, even causing death, if he reasonably apprehends grievous hurt or death.

• Defence of Property: If 'A' attempts to commit house-breaking by night, 'B' (the owner) has the right to cause death to 'A' if he reasonably apprehends that such house-breaking would result in grievous hurt or death to himself or others. However, if 'A' merely attempts to steal a fruit from 'B's garden, 'B' would not be justified in shooting 'A'. The right to cause death in defence of property is limited to specific grave offences like robbery, house-breaking by night, mischief by fire to a dwelling house, or theft/mischief/house-trespass under circumstances causing reasonable apprehension of death or grievous hurt.

• Cessation of Right: In Jai Dev v. State of Punjab, the Supreme Court emphasized that the right of private defence commences as soon as a reasonable apprehension of danger to the body arises from an attempt or threat to commit the offence, and it continues as long as such apprehension of danger continues. Once the aggressor retreats or is disarmed, the right ceases.

In essence, while the law grants individuals the power to protect themselves and their property, it simultaneously imposes a duty to exercise this power with restraint and reason, ensuring that justice is not replaced by vengeance.