This guide is maintained as a current resource for September 2026 and covers only the laws of England and Wales. Information is for general guidance, not legal advice. Consult a qualified solicitor for advice specific to your situation.
Learn what self defence is under criminal law in England and Wales, including how reasonable force, necessity and proportionality determine whether force used to protect yourself, another or property is lawful, and how courts apply this defence in practice.
Self defence is a fundamental legal principle in the criminal law of England and Wales that permits a person to use force to protect themselves, another person, property or to prevent a crime - provided specific legal criteria are met. It can be a complete defence to criminal charges involving the use of force; if successful, it can result in an acquittal even when the defendant admits the act. This article explains how the defence operates, the conditions that must be satisfied, how the law is applied by courts, and what practical questions commonly arise.
Why Self Defence Matters
In criminal prosecutions involving violence or force, the prosecution must prove beyond reasonable doubt that the defendant's conduct was unlawful. However, the law recognises that there are circumstances in which a person may justifiably use force - for example, where they genuinely believe they face an imminent attack and there is no safe alternative. Where those conditions are met, self defence operates not as an excuse but as a justification, meaning the force used is regarded as lawful.
Self defence is grounded in both common law and statute. Section 3(1) of the Criminal Law Act 1967 provides statutory authority for the use of reasonable force in the prevention of crime and in effecting or assisting a lawful arrest, while longstanding common law principles extend the defence to protect the person, others and, in some circumstances, property.
What Self Defence Means
Self defence allows a person to use reasonable and necessary force when they honestly and genuinely believe they or another person are under threat of unlawful force. The central legal test has two components:
- Necessity - the defendant must have believed it was necessary to use force to defend against an imminent threat; and
- Reasonableness - the level of force used must be proportionate to the perceived threat.
This principle applies whether the threat is to the defendant, another person, or in preventing a crime. The question of whether force was reasonable is ultimately a matter for the jury or judge, considering all relevant circumstances.
The Legal Framework
Statutory Law
Under Section 3(1) of the Criminal Law Act 1967, a person may use such force as is reasonable in the circumstances:
- To prevent crime, including stopping an assault;
- In effecting or assisting the lawful arrest of offenders or suspected offenders; and
- To defend property where a crime is ongoing.
This statutory defence operates alongside common law principles and is often used in conjunction with them.
Common Law Principles
At common law, self defence has developed through judicial decisions. The courts have established that the test of reasonable force balances the need for protection with the principle that force should not be excessive. These principles are applied by analysing the situation from the defendant's perspective at the time of the threat, including any mistaken beliefs that were genuinely held.
Key Elements of the Defence
1. Honest Belief in Threat
A defendant can rely on self defence if they genuinely believed that force was necessary to prevent harm. Importantly, this belief may be mistaken, and if it was honestly held at the time, it can still support the defence - even if it later proves to be incorrect.
However, where a defendant's mistaken belief is caused by voluntary intoxication, the defence may not apply to justify the use of force. In cases such as R v O'Grady, courts have held that drunken mistakes cannot support a self defence claim if they led to the use of unreasonable force.
2. Immediacy and Necessity
The threat must be imminent - meaning an attack is genuinely underway or about to occur. The force used must be necessary, in the sense that the defendant had no reasonable alternative at that moment to avoid harm. This reflects the idea that force should only be used when there is no safe escape or alternative action.
3. Reasonable and Proportionate Force
The force used must be proportionate to the perceived threat. Courts assess reasonableness by reference to:
- The level of danger the defendant believed they faced;
- The type and extent of force used; and
- Whether the force was more than was necessary to avert the threat.
In a household context, law reforms have introduced a modified test where force that is disproportionate but not grossly disproportionate may still, in certain circumstances, be accepted as lawful when used by a householder defending against intruders. This is sometimes referred to in public discourse as the householder defence.
Defence of Others and Property
Self defence can extend beyond protecting oneself:
- Defence of another person: A person may use reasonable force to protect someone else from imminent harm, applying the same tests of necessity and proportionality as for personal self defence.
- Defence of property: Reasonable force may be used to prevent a crime against property or to stop an ongoing crime such as burglary. However, this does not justify excessive force merely to protect property without an imminent threat of personal harm.
How Self Defence Is Applied in Practice
Burden and Standard of Proof
While self defence is raised by the defendant, the burden of proof remains with the prosecution, which must prove beyond reasonable doubt that the defendant did not act in lawful self defence. The defendant is not required to prove that they did act in self defence - they only need to raise enough evidence for the issue to be considered by the court.
Excessive Force and Criminal Liability
If the force used is clearly unreasonable or disproportionate, the defence will fail, and the defendant may be convicted of the offence charged. For example, continuing to use force after the threat has ceased or using force that is significantly greater than necessary will likely be regarded as unlawful.
Common Questions About Self Defence
Is there a duty to retreat?
No general duty to retreat exists in English law. Although courts may consider whether retreat was possible when assessing reasonableness, a person is not legally obliged to flee from their home or a threat before acting in self defence.
Can you use objects to defend yourself?
Yes, a person may use everyday objects at hand to assist in self defence if doing so involves reasonable force in the circumstances. However, carrying offensive weapons in anticipation of defence is not lawful.
Does self defence apply to all offences?
Self defence is primarily a defence to offences involving the use of force - such as assault and battery. It does not generally apply to non‑violent offences like burglary where no force was used.
Key Takeaways
Self defence in the criminal law of England and Wales allows individuals to lawfully use reasonable and necessary force to protect themselves, others, property, or to prevent crime. To succeed, the defence requires that the defendant genuinely believed force was necessary, that the threat was imminent and that the force used was proportionate to that threat. Self defence is a complete defence - if established on the evidence, it leads to acquittal. Courts assess these factors carefully, taking into account both subjective belief and objective reasonableness in the circumstances.
