You can kill someone in self-defense no matter how minor the attack was.

The law only allows killing in self-defense for serious attacks listed in Section 38, like ones that could cause death or grievous hurt. For lesser attacks, you can only cause harm short of death.

Section 39 means you can't defend yourself at all if the attack isn't serious.

You can still defend yourself and cause some harm to the attacker; you just can't go as far as killing them, and your response must stay within reasonable limits under Section 37.

Bharatiya Nyaya Sanhita, 2023

Section 39

When such right extends to causing any harm other than death

If the offence be not of any of the descriptions specified in section 38, the right of private defence of the body does not extend to the voluntary causing of death to the assailant, but does extend, under the restrictions specified in section 37, to the voluntary causing to the assailant of any harm other than death.§

Why this exists

This provision continues a long-standing principle from the Indian Penal Code (Section 101), which recognized that the right of private defence must be proportionate to the threat faced. Lawmakers wanted to prevent people from using lethal force in response to minor attacks, while still allowing them to protect themselves using reasonable, non-lethal force. It balances the individual's right to self-protection against the state's interest in preventing unnecessary loss of life.

How courts read it

Indian courts, interpreting the identical predecessor provision (IPC Section 101), have consistently held that the right of private defence is not a right to retaliate or take revenge, but only to repel an imminent threat. Courts have emphasized that the force used must be proportionate to the danger apprehended, and if the original attack does not fall within the serious categories listed (now in Section 38), causing death in response will not be protected under private defence, even if some non-lethal defensive harm is justified.

Common misconceptions

Myth: You can kill someone in self-defense no matter how minor the attack was.
Fact: The law only allows killing in self-defense for serious attacks listed in Section 38, like ones that could cause death or grievous hurt. For lesser attacks, you can only cause harm short of death.
Myth: Section 39 means you can't defend yourself at all if the attack isn't serious.
Fact: You can still defend yourself and cause some harm to the attacker; you just can't go as far as killing them, and your response must stay within reasonable limits under Section 37.