Self-defence in English law is the use of force to protect oneself or another person from unlawful violence. It is part of the wider law of Reasonable force, which also covers defence of property, prevention of crime, and assisting lawful arrest.
The law does not require a person under attack to make perfect calculations. It asks whether force was necessary and reasonable in the circumstances as the person honestly believed them to be.
Legal Basis
Self-defence comes from common law. Section 76 of the Criminal Justice and Immigration Act 2008 sets out how courts should approach reasonable force where self-defence, defence of property, prevention of crime, or lawful arrest is in issue.
Section 3 of the Criminal Law Act 1967 separately allows reasonable force to prevent crime or to effect or assist a lawful arrest.
Core Questions
The main questions are:
- Did the person honestly believe force was necessary?
- Were the circumstances as they believed them to be capable of justifying force?
- Was the type and amount of force reasonable?
- Was the force defensive, rather than revenge or punishment?
The reasonableness of a belief can be evidence of whether the belief was genuinely held, but a genuinely held mistaken belief can still be considered unless it was caused by voluntary intoxication.
No Duty to Retreat
There is no strict duty to retreat before using defensive force. The possibility of retreat can be considered where relevant, but it does not automatically defeat self-defence. In a sudden attack, a person may have little time to withdraw.
Exact Measure of Force
Section 76 recognises that a person acting for a legitimate purpose may not be able to weigh the exact measure of necessary action. Evidence that a person did only what they honestly and instinctively thought necessary is strong evidence that reasonable action was taken.
That principle has limits. In non-householder cases, disproportionate force is not reasonable. In householder cases, grossly disproportionate force is not reasonable.
Defence of Another Person
Self-defence includes acting in defence of another person. A person who intervenes to stop an assault may rely on the same general principles, judged by the facts as they honestly believed them to be.
Weapons and Improvised Objects
Using an object in self-defence is not automatically unlawful. The law looks at why the object was present, what threat existed, how serious the danger was, what the person believed was happening, and what force was used.
There is a major difference between:
- Carrying a weapon in public in advance for possible future protection.
- Using an object already lawfully present during an immediate attack.
The first situation can create offensive weapon or bladed article problems. The second may be judged mainly as reasonable force, although every fact still matters.
Serious Attacks
Where a person is being punched, kicked, stamped on, outnumbered, trapped, or attacked near traffic or hard ground, the risk of serious injury or death can be real. Defensive force in that setting may be assessed differently from force used in a minor argument.
Example:
- A person is knocked to the ground and two attackers continue kicking or stamping towards the head. The person may honestly believe they are at risk of death or serious injury. Force used to escape or stop the attack would be judged in that context, not as if the person had time to calmly choose the least forceful option.
Folding Pocket Knives
A small non-locking folding pocket knife with a cutting edge of 3 inches or less may be outside section 139 of the Criminal Justice Act 1988. That does not mean it is sensible or lawful to carry it for self-defence.
If the knife is carried for ordinary lawful tasks and an immediate life-threatening attack occurs, any use or threatened use would be judged under self-defence principles. If the knife is carried because the person wants a weapon available, the offensive weapon issue becomes much stronger.
Smoke Devices and Escape
A person may try to escape violence by creating distance, attracting attention, or confusing attackers. If a smoke device or similar item is used during an immediate attack, that context may matter to public-order, criminal-damage, and reasonable-force questions. It does not mean every consequence is automatically excused, especially if property is damaged or bystanders are put at risk.
Practical Examples
Push to Escape
A person is cornered and pushes an attacker away to run. That may be reasonable defensive force.
Continued Attack After Danger Ends
A person disarms an attacker, the attacker backs away, and the defender then chases and beats them. The later force may be treated as retaliation rather than defence.
Outnumbered on the Ground
A person is on the pavement while two attackers punch and kick them. Stronger defensive force may be reasonable because the perceived danger is much higher.
Producing a Knife During a Minor Argument
A person produces a knife during a shouting match with no immediate physical threat. That is unlikely to be justified by self-defence and may create weapons and public-order offences.
Householder Cases
Householder cases have a special statutory rule. Force is not reasonable if it is grossly disproportionate. This gives householders some latitude when confronting intruders, but it does not permit revenge, execution, or violence after the danger has passed.
Relationship with Citizen's Arrest
Self-defence is not the same as Citizen's Arrest. A person may use reasonable force to protect themselves without arresting anyone. A citizen's arrest under section 24A of PACE has separate conditions and is narrower than many people assume.
See Also
- Reasonable force
- Citizen's Arrest
- Offensive weapon
- Bladed articles
- Folding pocket knife
- Public Order Act 1986
References
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