Self-defence is one of the most frequently raised defences in criminal practice. It governs when a person may lawfully use force to protect themselves, another person, or property — and when force tips over into a crime. For a solicitor advising a client charged with assault, wounding or even homicide, knowing precisely how this defence is built, and where its limits lie, is often the difference between acquittal and conviction.
The rules sit across the common law and statute, but they fit together into a clear, workable framework. This lesson takes you through it step by step:
- The Defence and Its Sources — what self-defence covers, its all-or-nothing effect, and who must prove what.
- The Two-Stage Test — the framework for assessing any claim: genuine belief in the need for force, then reasonableness of the force used.
- Belief in the Need for Force — why a genuine belief counts even if mistaken, and how intoxication affects this.
- Reasonableness of Force — how proportionate force is judged, retreat, pre-emptive strikes, and defence of property.
- Householder Cases — the relaxed standard for someone defending their home, and its conditions.
- Limits on the Defence — initial aggressors, retaliation after a threat has passed, and force used during an arrest.
By the end, you'll be able to take a set of facts and work out whether self-defence succeeds.