5 The justifiable defences

Private defence — force used to repel an unlawful attack, limited to what is necessary and proportionate; the right ends when the threat ends. Necessity — harm done to avoid a greater harm, where the actor had no lawful alternative; unlike private defence, the harm avoided need not come from a wrongdoer. Consent — where the harm is of a kind the law allows a person to consent to; consent obtained by fraud or fear is no consent. Legal authority — acts done by a public servant in the exercise of powers conferred by law, and acts done in execution of a court's order.