Self-defence is the use of force to protect oneself or another person from unlawful violence. In England and Wales it is mainly a common law defence, supported by statutory rules on reasonable force.
The central question is not whether the person was perfectly calm or made the best possible decision afterwards. The question is whether they honestly believed force was needed, and whether the force used was reasonable in the circumstances as they believed them to be.
England and Wales
Self-defence applies where a person uses force to defend themselves or someone else. Closely related rules cover defence of property, prevention of crime, and assisting a lawful arrest.
Section 3 of the Criminal Law Act 1967 allows a person to use force that is reasonable in the circumstances to prevent crime or to effect or assist a lawful arrest. Section 76 of the Criminal Justice and Immigration Act 2008 explains how courts assess reasonable force for self-defence, defence of property, prevention of crime, and lawful arrest.
Basic Test
The usual test has two parts:
- Did the person honestly believe that force was necessary?
- Was the force used reasonable in the circumstances as the person believed them to be?
The belief can be mistaken, but it must be genuinely held. The force is then judged against the circumstances as the person believed them, not with perfect hindsight.
Reasonable Force
Reasonable force is fact-specific. The same action may be lawful in one situation and excessive in another. Relevant factors include the threat, the number of attackers, weapons, size and strength, location, opportunity to escape, protection of others, and how quickly events unfolded.
People under attack are not expected to measure force with precision. A person may act instinctively in the heat of the moment. However, force used for revenge, punishment, or after the threat has ended is much harder to justify.
No Strict Duty to Retreat
There is no simple rule that a person must retreat before defending themselves. An opportunity to leave can still matter when deciding whether force was reasonable. If escape was easy and safe, continuing a confrontation may weaken a self-defence claim. If escape was not realistic, force may be easier to justify.
Householder Cases
Householder cases have a special statutory rule. In some home-intruder situations, force is not automatically unlawful merely because it was disproportionate. It cannot be grossly disproportionate. This rule does not give a licence to punish intruders. The court still looks at the circumstances as the householder believed them to be.
Weapons and Objects
Using an object as a weapon does not automatically make self-defence unlawful, but it increases scrutiny. A person who grabs an object during an unexpected attack may be judged differently from someone who arms themselves in advance and goes looking for confrontation.
Possession and use are separate questions. For example, section 139 of the Criminal Justice Act 1988 has an exception for a folding pocketknife with a cutting edge of three inches or less, provided it is genuinely folding and non-locking. That exception concerns possession under that section. Using any knife in a fight is a separate and much more serious question judged on necessity, reasonableness, and the facts at the time.
Clothing and Appearance
Unusual clothing, tactical-style clothing, face coverings, body armour, or dark clothing do not by themselves decide whether self-defence is available. They may become relevant if they show planning, intimidation, concealment, or lawful protective purpose. The legal question remains focused on the threat, the person's honest belief, and the force actually used.
Practical Examples
Multiple Attackers
A person is attacked by two people in the street and is being punched, kicked, and stomped. If they honestly believe serious injury is imminent, the law may allow significant defensive force. The reasonableness of any force will depend on what they believed, what options existed, and whether the force stopped when the danger stopped.
Distraction to Escape
A person uses a distraction to escape an ongoing attack rather than to injure the attackers. That may support necessity, although any public order, damage, or safety issue would still be judged on its own facts.
Retaliation After Escape
A person escapes, returns later with others, and attacks the suspected aggressor. That is no longer immediate self-defence. It is likely to be treated as retaliation.
Defence of Another Person
A witness sees someone being seriously assaulted and uses reasonable force to pull the attacker away or restrain them until police arrive. That may be justified as defence of another person, prevention of crime, and possibly assistance with lawful arrest.
Police and Members of the Public
Police officers and members of the public are both subject to the law on reasonable force. Police may have additional powers and duties, but the use of force still has to be justified. The CPS states in guidance on deaths in custody and police contact that police are subject to the same laws of self-defence and reasonable force as members of the public.
See Also
References
- Criminal Law Act 1967, section 3
- Criminal Justice and Immigration Act 2008, section 76
- Criminal Justice Act 1988, section 139
- Crown Prosecution Service: householders and use of force against intruders
- Crown Prosecution Service: deaths in custody, self-defence and reasonable force
- Ministry of Justice: defences, mitigation and criminal responsibility
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