Law of Torts
TORT 021 Private Defence and Necessity
Private Defence and Necessity: Reasonable Force Against an Aggressor, and Sacrifice of an Innocent Interest to Avert a Greater Harm
The two defences look alike and rest on opposite footings. Private defence is directed at an aggressor: a person may use reasonable force to protect his person, the person of another, or his property, against an imminent threat. Necessity is invoked against an innocent person whose interests are sacrificed to avert a greater harm. That difference explains why the two produce different results on compensation: a person who repels an attack owes the attacker nothing, while a person who saves himself at an innocent stranger's expense is ordinarily liable to pay for the damage he caused, even though his act was justified.
The three defences, and the two cases marking the boundary of necessity
1. Private Defence
- A person may use reasonable force to defend his own person, the person of another, and his property, real or personal.
- The force must be proportionate to the threat. The law does not weigh it in golden scales, but it will not permit a response out of all proportion to what was faced.
- The threat must be imminent. There is no right of pre emptive attack, and once the danger has passed the right of defence ends with it. Force used thereafter is retaliation, not defence.
- Excessive force makes the defender himself a wrongdoer, and liable for so much of the harm as the excess caused.
- There is no duty to retreat from one's own home, and English and Indian law have never required a person attacked to run away before defending himself.
- Force may be used to defend property, but the law values life and limb above property, so force likely to cause death or grievous harm is not justified merely to protect goods.
- A trespasser may be removed with reasonable force, after a request to leave where circumstances permit one.
- Bird v. Holbrook (1828) marks the outer limit on the property side. A concealed spring gun set without notice was held unjustified, because its object was to injure rather than to deter, and the harm it was calculated to inflict was out of all proportion to the trespass it was meant to prevent.
- Setting a dangerous thing to protect property is therefore lawful only where it is proportionate and, ordinarily, where notice of it is given.
2. Necessity
- The defence justifies an interference with an innocent person's rights in order to avert a greater harm.
- It requires a real and imminent danger, and an act that was reasonably necessary to meet it at the time it was done.
- It is judged as the situation appeared then, not with hindsight. It does not matter that the danger did not in the event materialise, if a reasonable person would have acted as the defendant did.
- An honest belief that the act was necessary is not enough. The belief must be reasonable, and the act must in fact have been reasonably necessary.
- The defence is divided into private and public necessity, and the division matters chiefly for compensation.
Private necessity | Public necessity | |
Whose interest is protected | The defendant's own person or property | The community, or a section of it |
The classic instance | Tying a boat to another's jetty in a storm; entering land to escape a danger | Pulling down a house to stop the spread of a fire; destroying goods to prevent contagion |
Effect on the claim in trespass | A justification: the act is not wrongful | A justification: the act is not wrongful |
Liability to pay for the damage | Ordinarily yes. The defendant must compensate for the damage he caused | Ordinarily no, at common law |
Why the difference | He saved his own interest at the plaintiff's expense | He acted for all, and the community should bear the cost |
The modern position | Statute usually provides for compensation in the public cases, so the common law rule is of limited practical importance |
3. The Two Cases That Mark the Boundary
📖 Cope v. Sharpe (No. 2) [1912] 1 KB 496 Facts A fire broke out on the plaintiff's land, on which the defendant's master had shooting rights. The defendant, a gamekeeper, entered the land and burned strips of heather to make a firebreak, in order to prevent the fire from reaching the nesting pheasants. The plaintiff's own servants extinguished the fire before it reached the strips, so the firebreak turned out to have been unnecessary in the event. Held The defendant was not liable in trespass. The defence of necessity succeeded. Ratio Where there is a real and imminent danger, and what the defendant does is reasonably necessary to meet it as the situation appears at the time, the act is justified. It is immaterial that the danger did not in the event materialise, or that the precaution proved in hindsight to have been unnecessary. The test is applied at the moment of action, not afterwards. |
📖 Kirk v. Gregory (1876) 1 Ex D 55 Facts On the death of the occupier of a house, while a good deal of drinking and disorder was going on, his sister in law removed his jewellery from one room to another, believing it would be safer there. It was stolen from the second room. The executor sued her in trespass to goods. Held She was liable in trespass, though the damages were nominal. The defence of necessity failed. Ratio An honest belief that an interference with another's goods was necessary is not enough. The interference must in fact have been reasonably necessary in the circumstances, and here it was not. The case is the standard contrast to Cope v. Sharpe, and shows that the defence is not satisfied by good intentions. |
4. The Two Defences Compared
Private defence | Necessity | |
Against whom | An aggressor, who is himself a wrongdoer | An innocent person, whose interest is sacrificed |
What it answers | The aggressor's claim in trespass or battery | The innocent person's claim in trespass |
The trigger | An imminent unlawful threat | A real and imminent danger, not necessarily caused by anyone |
The limit | Reasonable and proportionate force | Reasonably necessary action, judged at the time |
Compensation | None payable to the aggressor | Ordinarily payable in private necessity; not at common law in public necessity |
If excessive | The defender becomes a wrongdoer to the extent of the excess | The defence fails and the act is a trespass, as in Kirk v. Gregory |
The leading case | Bird v. Holbrook marks the outer limit | Cope v. Sharpe (No. 2), with Kirk v. Gregory on the other side |
5. Necessity in Medical Treatment
- It supplies the justification where consent cannot be obtained. A patient who is unconscious, or otherwise unable to decide, cannot consent, and without some justification the treatment would be a battery.
- The treatment must be necessary and must not be postponable until the patient can decide for himself.
- It is confined to what the emergency requires. A surgeon who, during an authorised operation, performs a further procedure for convenience rather than necessity acts outside the defence.
- A known refusal displaces it. Where the patient has, while competent, refused the treatment in question, necessity does not authorise giving it.
6. The Common Test
⚠ Reasonableness measured at the moment of action Both defences turn on the same underlying question, and both are judged as the situation appeared at the time and not with the benefit of hindsight. Was there a real and imminent danger? And was what the defendant did reasonably necessary, or reasonably proportionate, to meet it? Cope v. Sharpe makes the point about hindsight explicitly: the gamekeeper succeeded although the fire never reached the firebreak, because the question was what a reasonable person would have done when the fire was burning. Kirk v. Gregory makes the converse point about good faith: the defendant genuinely believed she was helping, and failed, because a sincere belief is not the same as a reasonable necessity. The defence is objective on both sides of the line. |
7. The Position Stated Shortly
1. Private defence permits reasonable force to protect the person, the person of another, or property, against an imminent threat.
2. The force must be proportionate, the threat must be imminent, and excessive force makes the defender himself a wrongdoer.
3. There is no duty to retreat from one's own home, and force likely to cause death is not justified merely to protect goods.
4. Bird v. Holbrook marks the limit: a concealed spring gun set without notice was unjustified.
5. Necessity justifies an interference with an innocent person's rights to avert a greater harm.
6. It requires a real and imminent danger and an act reasonably necessary to meet it, judged as matters appeared at the time.
7. Cope v. Sharpe (No. 2) succeeded although the danger never materialised; Kirk v. Gregory failed although the defendant acted in good faith.
8. In private necessity the defendant is ordinarily liable to pay for the damage he caused, though the act was justified.
9. In public necessity no compensation was payable at common law, and statute usually provides for it instead.
10. Necessity supplies the justification for emergency medical treatment where the patient cannot consent, confined to what the emergency requires.