General defences - Self-defence and defence of another

Learning Outcomes

This article sets out a thorough understanding of self-defence and defence of another in criminal law under English law, addressing:

• The scope and universal applicability of self-defence and defence of another across all criminal offences, including homicide, non-fatal offences, and property crimes.
• The dual requirements of necessity (necessity of force, including assessment of honest, subjective belief and immediacy of threat) and reasonable force (objective standard, proportionality, assessment against both common law and statute).
• The complete statutory and common law legal framework, notably s 3 Criminal Law Act 1967 and s 76 Criminal Justice and Immigration Act 2008, and judicial interpretation—especially relating to pre-emptive strikes, situations of retreat, and timing.
• The treatment of mistaken belief (including highly unreasonable or delusional beliefs and intoxication-induced errors), differentiating honest mistakes from those barred by voluntary intoxication.
• Special considerations and statutory latitude for householders under the CJIA 2008, including what constitutes grossly disproportionate force, and assessment in relation to home intruders.
• The role and scope of defensive force where safeguarding third parties, and the constraints governing force to protect property.
• The full procedural operation of the legal and evidential burdens of proof: defence’s evidential burden to make self-defence an issue; prosecution’s legal burden to disprove the defence to the criminal standard.
• Cross-cutting issues, including case law direction on the all-or-nothing nature of self-defence, the potential overlap or contrast with other defences or partial defences (especially in homicide), the effect of excessive force, avenues for mitigation, and detailed, stepwise problem analysis for application to a range of fact patterns.

SQE1 Syllabus

• legal requirements and universal applicability of self-defence and defence of another to all criminal offences, including homicide and property crimes
• necessity of force: subjective honest belief, requirements of imminence, factual mistakes, impact of delusional beliefs
• reasonable force: proportionality of response, objectivity, heat of the moment, assessment under stress, statutory clarifications
• mistaken belief: the test for sincerity, the irrelevance of reasonableness (unless belief induced by voluntary intoxication), cases of psychiatric disturbance
• interaction between voluntary/involuntary intoxication and mistaken belief in necessity of force
• statutory provisions: s 3 Criminal Law Act 1967, s 76 Criminal Justice and Immigration Act 2008 (CJIA 2008), and the special householder rules including the grossly disproportionate force test
• limitations of the defence: excessive or retaliatory force, timing, use in revenge or when threat has passed
• no duty to retreat but importance of attempts to avoid conflict; pre-emptive strikes and assessment of immediacy
• interaction between prevention of crime/defence of property and self-defence
• legal and evidential burdens of proof—including proper allocation and shift of onus at trial
• practical application: fact patterns, stepwise identification of legal issues, common pitfalls in application, critical analysis per syllabus requirements

Test Your Knowledge

Attempt these questions before reading this article. If you find some difficult or cannot remember the answers, remember to look more closely at that area during your revision.

1. What are the two main requirements that must be established for self-defence or defence of another to succeed in law?
2. Can a defendant rely on self-defence if they honestly believed force was necessary, even if their belief was unreasonable?
3. What is the effect of voluntary intoxication on a mistaken belief in the need for self-defence or defence of another?
4. In householder situations, under what circumstances may force be disproportionate, and when does the defence fail?
5. Who bears the legal and evidential burdens at trial when self-defence is raised?

Introduction

Self-defence and defence of another are fundamental and complete general defences available to all criminal offences in England and Wales. These defences provide legal justification for conduct (often otherwise criminal) where justified force is used to prevent harm to oneself, to another, or—subject to strict constraints—to protect property or prevent the commission of crime. The legal approach reflects a balance: on one hand, the law recognises the right to personal autonomy and safety, and on the other, it places limits on violence to preserve order and prevent abuses under the pretext of protection.

Key Term: self-defence
A general defence permitting a person to use reasonable force to protect themselves, another person, or, in specific circumstances, property, provided the use of force was necessary and honestly, even if mistakenly, believed to be so.

The Legal Basis for Self-Defence

The legal basis for self-defence and related defences is found in a combination of common law rules and important statutory provisions:

• Section 3 Criminal Law Act 1967: Authorises the use of “such force as is reasonable in the circumstances in the prevention of crime, or in effecting or assisting in the lawful arrest of offenders or suspected offenders.”
• Section 76 Criminal Justice and Immigration Act 2008 (CJIA 2008): Codifies and clarifies the operation of self-defence, including the test for necessity, proportionality, honest mistaken belief, and the latitude allowed in householder cases involving intruders.

While self-defence developed at common law, s 3 CLA 1967 and s 76 CJIA 2008 now comprehensively govern its operation. Both acts cover the use of force, not only in defence of individuals but also in the prevention of crime and the arrest of (suspected) offenders. The substance of the defence and the burden of proof are governed by the interlocking statutory and common law principles.

Key Term: reasonable force
Force that is objectively proportionate to the threat as the defendant honestly believed it to be, assessed with appreciation for the circumstances as perceived by the defendant.

Key Term: necessity
Refers to the honest (subjective) belief that the use of force is needed to avert an imminent threat of harm to the defendant or others, or to prevent crime or protect property.

Statutory Framework

• s 3 Criminal Law Act 1967: “A person may use such force as is reasonable in the circumstances in the prevention of crime, or in effecting or assisting in the lawful arrest of offenders or suspected offenders.”
• s 76 Criminal Justice and Immigration Act 2008 (CJIA 2008): Consolidates previous case law and clarifies self-defence’s scope, applicable in all criminal proceedings. Section 76(2) expressly ties the statutory clarifications to common law self-defence, defence of another, defence of property, and the statutory defence under s 3 CLA 1967.

Section 76 CJIA 2008 makes clear that:

• Whether the force used was necessary, and its reasonableness, is judged according to the facts as the defendant honestly believed them to be (subjective).
• An unreasonable or even mistaken belief may suffice, unless such mistake was induced by voluntary intoxication.
• A pre-emptive strike may amount to reasonable force if the defendant honestly anticipates imminent danger.
• There is no duty to retreat, but evidence that the defendant tried to do so may be relevant in assessing necessity.

The law stipulates that mistakes based on voluntary intoxication are disregarded for the purposes of necessity.

Requirements for Self-Defence

To establish self-defence or defence of another, two principal conditions must be met:

• The defendant must have honestly believed that it was necessary to use force (subjective and genuine necessity).
• The force used must be reasonable in the circumstances as the defendant honestly believed them to be (objective proportionality, determined in light of those perceived circumstances).

Necessity of Force

The touchstone for necessity is the defendant’s honest belief in the need to act. This is a subjective test: the key question is what the defendant believed at the time, not whether that belief was sensible or reasonable to an outside observer. The defendant need not be correct in their belief; all that is required is that they genuinely held it. The belief may be mistaken, unreasonable, or even irrational (unless it was induced by voluntary intoxication).

Necessity also requires that the threat must be imminent—force is only justified to avert danger that is presently occurring or immediately impending. There is no requirement for the defendant to wait for physical violence; apprehension of an imminent threat suffices. In certain circumstances, a defendant’s psychiatric condition may supply strong evidence of their honest belief in the need to use force, though the law does not generally permit psychiatric delusions as justification unless the belief is honestly held (see R v Oye).

Key Term: mistaken belief
An honest, if mistaken, belief held by the defendant in the necessity of force. So long as this belief was genuinely held (and not due to voluntary intoxication), the defendant may rely on self-defence, even if mistaken or unreasonable.

Key Term: imminence
The threat faced by the defendant or another must be imminent—meaning immediate or rapidly approaching—not distant or hypothetical. The threat must not be entirely in the past, nor a vague future risk.

It is not necessary that the defendant faces an actual attack. A genuinely anticipated immediate risk suffices, and the use of force in a pre-emptive strike can be lawful.

Duty to Retreat

The law does not impose an obligation on a person to retreat from imminent danger before acting in self-defence. However, evidence that the defendant attempted to retreat or to avoid conflict may support the claim that actions were defensive rather than retaliatory. This is not a legal requirement but a factor the jury may consider when deciding if the defendant honestly believed force was necessary.

Pre-emptive Strikes

A person is not required to wait until they are struck before defending themselves (or another) if an attack is imminent. Anticipatory or pre-emptive force may be justified if it is reasonable in all the circumstances as believed by the defendant.

Worked Example 1.1

Necessity Scenario

Alicia, on seeing someone running towards her brandishing a broken bottle, punches them before they can strike.

Answer:
If Alicia honestly believed she was about to be attacked and her belief was honestly held (regardless of whether it was reasonable), force may be necessary. If the punch was a proportionate response to the threat as Alicia perceived it, she may succeed with the defence of self-defence.

Reasonable Force

After showing that force was necessary, it remains to be shown that it was reasonable in the circumstances as perceived by the defendant. This is an objective assessment, albeit with reference to the defendant’s subjective perception. The reasonableness of force is evaluated in light of all circumstances, including the urgency and pressure of the moment. The law recognises that a person faced with a dangerous situation cannot be expected to weigh to a nicety the exact amount of force needed.

Key clarifications from s 76(7) CJIA 2008:

• If the defendant’s response was honestly and instinctively believed to be necessary, this is strong evidence that only reasonable action was taken.
• The greater the threat (e.g., a threat to life), the more force may be judged reasonable.
• Disproportionate or excessive force is not permitted, except where the special householder rules apply (see below).

Objectively, if the response was proportionate to the perceived risk, the force will be reasonable. While blunt or substantial force may be justified against a severe danger, the continued use of force beyond what is needed (for example, after the threat has passed) is not protected.

Key Term: proportionality
The legal requirement that force must be balanced and not excessive in relation to the threat faced, judged by reference to all circumstances as the defendant believed them to be.

Worked Example 1.2

Reasonable Force Scenario

Sam is attacked in a car park by an assailant wielding a knife. Sam knocks the attacker down with a metal bar. He continues to hit the attacker repeatedly after they drop the weapon and are incapacitated.

Answer:
The initial defensive act—striking the assailant to disarm or disable them—may be deemed reasonable, especially if Sam genuinely believed he was in imminent danger. However, repeated blows administered after the threat has abated go beyond what is reasonable in the circumstances and will usually amount to excessive force, causing the defence to fail for the latter acts.

Mistaken Belief in Need for Self-Defence

If a defendant was mistaken as to the need for defensive force (e.g., misidentifying the threat or misperceiving another’s actions), they may still rely on self-defence if their belief—however mistaken or unreasonable—was honestly held. The more unreasonable or illogical the belief, the less likely the jury is to find it was genuinely held.

Mistaken belief must be genuinely held, regardless of its reasonableness, except that mistakes resulting from voluntary intoxication cannot support the defence (see s 76(5) CJIA 2008 and O’Grady [1987]).

Delusional or Psychiatric Mistaken Beliefs

Where a defendant’s mental state includes psychiatric or delusional features (as in R v Oye), these can be relevant to whether belief in necessity was genuine. However, the law sets limits: where psychiatric symptoms cause a defendant honestly (but irrationally) to believe that force is necessary, courts focus on whether the belief was actually and sincerely held, not whether it was reasonable or logical. Delusional mistaken beliefs not induced by intoxication may satisfy the test, but may also overlap with the defence of insanity in appropriate cases.

Worked Example 1.3

Psychiatric Mistaken Belief Scenario

Bryan, who suffers from paranoid delusions, honestly but unreasonably believes his neighbour is about to attack him with a spade. He strikes first.

Answer:
On the evidence, if Bryan’s psychiatric condition leads him to genuinely believe he is threatened, that belief, however unreasonable, may suffice for the purpose of self-defence. The key question is sincerity of the belief, not reasonableness. However, if the belief was truly divorced from reality, and evidence met the legal threshold, a plea of insanity might be more appropriate.

Role of Intoxication in Self-Defence

In the context of voluntary intoxication, any mistaken belief arising from intoxication cannot found a claim to self-defence (CJIA 2008, s 76(5)). This covers both specific and basic intent offences, with the defence failing if the mistake is owing to alcohol or drugs voluntarily taken. Involuntary intoxication (such as being unwittingly drugged) does not preclude reliance on genuinely held misconceptions.

Key Term: voluntary intoxication
The self-induced consumption of intoxicating substances (alcohol or drugs) knowing their possible effects; the law excludes from self-defence any mistake as to necessity of force caused thereby.

The defendant will not be protected by self-defence if, as a result of being drunk or high, they misinterpret a threat and use force in circumstances which a sober person would not. This policy is rooted in public interest and protection from defendants seeking to exploit their own impaired judgment.

Worked Example 1.4

Intoxicated Mistaken Belief Scenario

Clive, who has drunk excessively, mishears a stranger's greeting for a threat and lashes out.

Answer:
Although Clive may claim he believed he was under threat, if this mistaken belief was induced by his own intoxication, he cannot avail himself of self-defence.

Retreat, Pre-Emptive Strikes, and Timing

No legal duty exists for a defendant to retreat before using necessary force, but evidence of an attempt to avoid violence may help the defence. Use of force in retaliation, after the threat has subsided, is never justified. The law also permits a pre-emptive strike where force is applied in anticipation of an immediate attack honestly believed to be impending.

Key Term: pre-emptive strike
The use of force in anticipation of an imminent attack; lawful only where the threat was immediate and belief in necessity was honestly held.

Worked Example 1.5

Pre-Emptive Strike Scenario

Maya, followed by a group late at night, believes an assault is imminent. She pre-emptively pushes one of the group into the road, injuring them.

Answer:
If the threat truly appeared imminent to Maya and she honestly believed her actions necessary, her response—though pre-emptive—may be justified as self-defence, provided the force used was reasonable in the circumstances as she believed them.

Special Rules for Householders

The law recognises that householders confronted with an intruder in their dwelling may be entitled to greater latitude than non-householders. Section 76(5A) CJIA 2008 (inserted by s 43 Crime and Courts Act 2013) establishes that, in a householder case:

• Force which is “disproportionate” may be reasonable, but grossly disproportionate force is always unreasonable.
• Force used must be in self-defence or defence of another, or in the prevention of crime or effecting a lawful arrest.
• The defendant must be in, or partly in, a building that is a dwelling, and the force must be directed against a trespasser (or someone the defendant honestly believes to be one).
• The perpetrator of the force must not themselves be a trespasser.

The special latitude reflects the stressful, urgent nature of defending oneself or family from intruders in one’s home, where a precise calibration of force may be impractical.

Key Term: definition of householder case
Applicable where (a) the defendant was in, or partly in, a building used as a dwelling, (b) the force was used to protect self or another from an intruder, and (c) the person against whom force was used was a trespasser (or reasonably believed to be).

The legal test (see R v Ray [2017]) is two-fold in such cases:

• Was the force grossly disproportionate? If yes, the defence fails.
• If not, was the force nonetheless reasonable in all the circumstances as the defendant genuinely believed?

The fact that force was “only” disproportionate does not, by itself, deprive the defendant of the defence. However, if the force is grossly disproportionate, the defence will not be available.

Worked Example 1.6

Householder Defence Scenario

Jordan, awoken by an intruder in the night, chases them through the house and strikes them with a lamp, then continues the assault outside as they attempt to flee.

Answer:
While within the dwelling, Jordan may be entitled to use disproportionate (though not grossly disproportionate) force if the circumstances justify it. However, once the intruder is retreating and the use of force moves outside the dwelling or continues after the threat has passed, such force will usually be excessive, and the householder defence would likely not apply for that part of the conduct.

Limits of the Defence

• Excessive or Grossly Disproportionate Force: For non-householders, any force exceeding what is reasonable in the perceived circumstances defeats the defence. Householders may use disproportionate force so long as it is not grossly disproportionate.
• Retaliation or Revenge: Force used after the danger has passed, or to exact revenge or punishment, is not protected and voids the defence.
• Immediacy: The threat must be imminent. Force used because of a past or remote threat, or speculative future threat, will not justify the defence.
• Intoxication-Induced Mistake: Any error as to the need for or level of force, induced by voluntary intoxication, is disregarded and cannot justify the defence of self-defence.
• All-or-Nothing Principle: Self-defence is a complete defence. If the use of force was excessive (even slightly), the defence is lost entirely and cannot partially justify the action (R v Clegg [1995]), except in homicide where the partial defences may become relevant.

Key Term: grossly disproportionate force
Force so extreme that it cannot, in any circumstances, be justified—even in householder cases; where so, the defence fails outright.

Worked Example 1.7

Householder Defence Limits Scenario

Lena, defending her home, stabs a burglar multiple times after they are incapacitated.

Answer:
The initial defensive force might be justified in the circumstances. However, continued stabbing after any threat is neutralised would almost certainly be seen as grossly disproportionate (especially in light of R v Ray), leading to the failure of the householder defence.

Exam Warning: Force and Defence Failure

Once force becomes excessive, however slightly, self-defence as a complete defence is unavailable and the defendant is liable for the offence charged. Although the threshold for householders is somewhat more generous, the question of whether force is grossly disproportionate or otherwise unreasonable is always a matter for the jury.

If the defence is unavailable because of excessive force, but the charge is homicide, alternative partial defences such as loss of control or diminished responsibility may, in exceptional circumstances, reduce liability to voluntary manslaughter (but these are not forms of partial self-defence).

Defence of Another: Application and Rules (Safeguarding a Third Party)

The defence of another mirrors entirely the law and principles of personal self-defence. Any person may use reasonable force to protect another, regardless of relationship, where it appears to be necessary in the circumstances, judged subjectively according to the defender's honest beliefs as to the threat.

• The defendant must honestly believe the other person was in immediate or imminent danger, even if mistaken.
• As with self-defence, the force used must be reasonable and proportionate as objectively assessed on the facts as perceived by the defendant.
• This right to protect others extends, exceptionally, beyond immediate family and includes strangers.

Reasonable force may also be used by a third party coming to the defence of another to prevent crime under s 3 CLA 1967. The same tests and limitations apply.

Worked Example 1.8

Defence of Another Scenario

Patrick witnesses a stranger being violently assaulted in a park and intervenes, striking the attacker with a stick which incapacitates the assailant.

Answer:
If Patrick genuinely believed the person was in immediate danger and his response was proportionate as to the threat as he believed it, the defence of another may apply—even if he was mistaken as to the situation, provided his belief was genuinely and honestly held.

Defence of Property: Special Considerations

English law does not recognise a right to use serious or life-threatening force solely to protect property. While reasonable force may be used to defend possessions, the law draws a sharp distinction between force justified to protect persons and that justified to protect property alone.

• Force must remain proportionate to the perceived threat; serious injury or death is not justified except where protection of property overlaps with defence of persons (e.g., where a burglar poses a direct threat to occupants).
• In householder cases, the special rules apply only if the threat is to people; force may not be grossly disproportionate.

Application: Legal and Evidential Burdens of Proof

Fundamental to the operation of self-defence and allied defences is the allocation and satisfaction of burdens of proof:

• The evidential burden lies with the defendant to adduce some evidence that raises the issue of self-defence, making it a live issue in the trial (even if arising out of prosecution evidence).
• Once raised, the legal burden reverts to the prosecution to disprove self-defence beyond reasonable doubt (see Woolmington v DPP [1935]), i.e., to establish that self-defence does not apply, either because no honest belief existed as to necessity, or because the force was not reasonable.

The defendant is not required to prove the defence is applicable; rather, if the jury is left in any doubt as to whether the defendant may have been acting in necessary and reasonable self-defence, the jury must acquit.

Only for the defence of insanity and certain statutory exception defences (not self-defence) will the legal burden shift to the defendant.

Key Term: burden of proof
The evidential burden for self-defence rests with the defendant (to raise it), but the legal (persuasive) burden to disprove self-defence always remains with the prosecution, to the standard of beyond reasonable doubt.

Worked Example 1.9

Burden of Proof Scenario

At trial, the defendant adduces evidence of a violent argument and a claim that she acted in self-defence. The prosecution lacks direct evidence to contradict her account.

Answer:
The judge must explain to the jury that, once such evidence is adduced, it is for the prosecution to satisfy them that the defendant was not acting in self-defence—if they are not sure, they must acquit.

Practical Application to Fact Patterns and Avoidance of Pitfalls

• When analysing problem scenarios, always consider both elements: necessity (honest belief in imminent or immediate threat) and the objective reasonableness of force.
• Be cautious about mistakes arising from intoxication, about actions after a threat has ceased (retaliation), and about force used in the recovery of property outside dwelling-householder provisions.
• Address both the subjective and objective prongs: would a sober person, in the defendant’s circumstances, have honestly believed the force necessary? Was the force, judged in the context, reasonable?

Worked Example 1.10

Application & Pitfalls Scenario

Marcus tackles a shoplifter in a supermarket, detains them with considerable (but non-lethal) force, and punches them repeatedly after they have stopped resisting.

Answer:
The initial restraint may amount to reasonable force in the prevention of crime under s 3 CLA 1967. However, repeated blows after the threat has subsided will likely be excessive and defeat the defence.

Summary Table: Self-Defence and Defence of Another

Key Point Checklist (Article Coverage) - Summary

This article has covered the following key knowledge points:

• Self-defence and defence of another are general defences available to all criminal offences, both against the person and property.
• The defence requires honest belief in the necessity for force, assessed subjectively, and that the force used was objectively reasonable and proportionate in the circumstances as the defendant believed them.
• Honest mistakes may be relied upon if genuinely held, but not if induced by voluntary intoxication.
• There is no duty to retreat; attempts to avoid violence may support but are not required for the defence.
• Disproportionate (but not grossly disproportionate) force may be reasonable in householder cases; otherwise, only reasonable force is permitted.
• Excessive or grossly disproportionate force defeats the defence; there is no partial defence or liability for “slightly excessive” force (except for the partial defences available in homicide).
• The same principles apply to the defence of another, but greater restrictions apply to force used solely to defend property.
• The defendant bears only an evidential burden to raise the defence; the prosecution must disprove self-defence beyond reasonable doubt.
• Defences of automatism or insanity may arise alongside or instead of self-defence, but their requirements and results are distinct.
• Mistakes as to the need for force or the amount of force must negate mens rea to found a defence; intoxication-based mistakes do not apply.
• Applicability must be evaluated carefully and contextually against fact patterns, with both limbs of the test applied.

Key Terms and Concepts List

• self-defence
• reasonable force
• necessity
• imminence
• mistaken belief
• proportionality
• voluntary intoxication
• pre-emptive strike
• grossly disproportionate force
• burden of proof
• definition of householder case