General defences

CRL.09 — General Defences

General defences negate liability where the prosecution has otherwise proved actus reus and mens rea. Distinguish complete defences (acquittal) from partial defences (loss of control, diminished responsibility — murder only, reducing to manslaughter; covered separately).

Self-defence / defence of another / property (complete)

Governed by the common law plus s.76 Criminal Justice and Immigration Act 2008 (and s.3 Criminal Law Act 1967 for crime prevention). Two limbs:

• Necessity (subjective): Was force necessary on the facts as D believed them to be? A genuine but mistaken belief works — even if unreasonable — unless the mistake is due to voluntary intoxication (O'Grady; s.76(5)).
• Proportionality (objective): Was the degree of force reasonable in those circumstances? In a householder case, grossly disproportionate force is never reasonable. Force falling short of that is not automatically lawful: the jury must still decide whether it was reasonable in the circumstances as D believed them to be. Disproportionate force may be reasonable in a householder case; in a non-householder case it cannot be (s.76(3), (5A), (6); R v Ray [2017] EWCA Crim 1391 at [24]-[29]). D need not wait to be struck; no duty to retreat (s.76(6A)).

Duress by threats (complete; NOT to murder/attempted murder/treason)

Two-stage Graham/Hasan test: (1) subjective — D reasonably believed in a threat of death or serious injury to self/family/those D is responsible for; (2) objective — a sober person of reasonable firmness sharing D's relevant characteristics would have given in. Threat must be imminent, no safe avenue of escape, and crime nominated. Bars (Hasan): voluntary association with violent criminals where coercion was foreseeable.

Duress of circumstances / necessity

Same two-stage test, threat arising from circumstances rather than a person (Pommell, Martin). True necessity is narrow (Re A).

Intoxication (a denial of MR, not a true "defence")

• Voluntary intoxication by alcohol or dangerous drugs: for a specific-intent offence (e.g. murder, s.18 OAPA 1861), the prosecution must still prove that D actually formed the required intent despite the intoxication. An intent formed while intoxicated still counts (Sheehan). For a basic-intent offence where recklessness suffices (e.g. assault, s.20 OAPA 1861), voluntary intoxication does not excuse the absence of awareness caused by it: ask whether D would have recognised the relevant risk if sober (DPP v Majewski; Judicial College, Crown Court Compendium, October 2025 updated March 2026, chapter 9, paras 5-6 and 13).
• A non-dangerous drug, such as a sedative: deliberately taking it is not automatically treated like drinking alcohol. If it is not commonly known to cause unpredictable or aggressive behaviour, consider whether D was subjectively reckless in taking it: aware of the risk of such behaviour in D's case but unreasonably running that risk. Consider the drug, dose and D's knowledge and experience. If that recklessness is proved, intoxication provides no defence to a basic-intent offence; otherwise its effects may be considered in deciding whether the prosecution has proved the required MR. This is not an automatic acquittal (R v Hardie [1984] EWCA Crim 2, [1985] 1 WLR 64; Compendium, chapter 9, paras 6(3) and 14).
• Involuntary intoxication: examples include a spiked drink or an unforeseen adverse reaction to genuinely prescribed medication. A prescription alone does not make every resulting intoxication involuntary. The prosecution must still prove the required MR: if D actually formed it, involuntary intoxication is no defence (Kingston). Ask what D actually intended or foresaw, not merely whether D had the capacity to do so (Compendium, chapter 9, paras 7-8 and 15).
• Dutch courage: no defence (Gallagher).

Insanity & automatism

• Insanity (M'Naghten): defect of reason from disease of the mind → D didn't know the nature/quality of the act, or that it was wrong. On the wrongfulness limb, D must show that D knew neither that the act was unlawful nor that it was wrong by the standards of ordinary reasonable people (R v Keal [2022] EWCA Crim 341, [41]-[42]; see also Lewis-Ranwell v G4S Health Services (UK) Ltd [2026] UKSC 2, [57]-[58]). Verdict: not guilty by reason of insanity. D bears the legal burden (balance of probabilities).
• Automatism: total loss of voluntary control from an external cause (sane automatism → acquittal). Internal cause = insanity. Self-induced automatism may bar the defence.

Common traps

• Mistaken self-defence belief from voluntary intoxication = no defence (s.76(5)).
• Duress is never available to murder (Howe) or attempted murder (Gotts).
• "Grossly disproportionate" applies only to householders, not all self-defence.
• Insanity reverses the burden onto D; most other defences D need only raise, then prosecution disproves.

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