Self-Defence
A complete defence available where the defendant uses reasonable force to defend themselves, another person, or property. The force must be necessary and proportionate. Criminal Law Act 1967 s.3 and common law.
Independent editorial summary — not the official statute text. Read the official version on legislation.gov.uk.
Ministry of Justice guidance summarises the current law: a person may use such force as is reasonable in the circumstances as he or she genuinely believed them to be, for self-defence, defence of another, defence of property, prevention of crime, or lawful arrest. Section 76 of the Criminal Justice and Immigration Act 2008 put part of the common law on self-defence (including defence of others) on a statutory footing, and later amendments confirm that a person is not under a duty to retreat when acting for a legitimate purpose — though the fact that they could have retreated remains a relevant factor in deciding whether the force used was reasonable.
Householders who confront an intruder in their own home get extra latitude: since section 43 of the Crime and Courts Act 2013, using a disproportionate level of force does not automatically make a householder a criminal. Grossly disproportionate force, however, remains unlawful in every case.
Example
Ministry of Justice guidance gives a worked illustration: a householder woken by breaking glass confronts a knife-wielding intruder, wrestles the knife away in a struggle, and — with adrenaline pumping as the intruder turns to flee — instinctively punches him on the back of the head, knocking him unconscious. The guidance says section 43 means the householder would not be guilty of an offence, even though the punch was arguably disproportionate to the now-retreating intruder's reduced threat, because it fell short of being grossly disproportionate.
Related terms
Official sources
This explanation is drawn from the official sources below; every substantive statement is verified against them. For advice on a specific matter, see our find help page.