Defences — self-defence, duress, necessity

Three defences provide complete acquittal when established. Self-defence (justificatory) requires: (1) honest belief that force was necessary (Williams); (2) objectively reasonable force in the circumstances as D believed them (s.76 CJIA 2008). Mistaken belief suffices unless attributable to voluntary intoxication. Duress (excusatory) requires: threat of death/serious injury; imminence with no escape; response a reasonable person would make; no voluntary association with criminals foreseeing risk of compulsion (Hasan). Unavailable for murder/attempted murder (Howe/Gotts). Necessity remains marginal, recognised only in Re A for extraordinary circumstances. The defences share a structure—complete acquittal where proven—but differ fundamentally: self-defence justifies (the act is not wrongful), duress excuses (wrongful but not culpable), while necessity's theoretical basis remains contested.

R v Palmer [1971] AC 814: Lord Morris established that defenders cannot 'weigh to a nicety' necessary defensive action when under attack. Foundational for modern self-defence doctrine—reasonableness assessed in the agony of the moment.

R v Williams (Gladstone) [1987] 3 All ER 411: Even unreasonable mistaken belief in need for force suffices if honestly held. Clarified subjective nature of first limb—D judged on facts as he believed them to be.

R v Hasan [2005] UKHL 22: Lord Bingham tightened duress requirements: threat must be imminent with no realistic escape; voluntary association with criminals foreseeing risk of compulsion defeats defence. Objective test ('ought reasonably to know') for voluntary association rule.

R v Howe [1987] AC 417: Duress unavailable for murder whether as principal or secondary party—ordinary person expected to sacrifice own life rather than kill innocent. Policy concerns about false claims and jury sympathy.

Re A (Children) [2001] Fam 147: Court authorised separation of conjoined twins knowing one would die. Only modern appellate recognition of necessity, though judges diverged on rationale. Ward LJ's three-stage test: act needed to avoid inevitable evil; no more done than necessary; evil inflicted not disproportionate.

Self-defence analysis: (1) Did D honestly believe force necessary? Consider reasonableness as evidence of honesty. (2) Was force objectively reasonable in circumstances D believed? Apply s.76(7)—allowance for split-second decisions. For householders against trespassers, force unreasonable only if grossly disproportionate (s.76(5A)).

Duress analysis: (1) Threat of death/serious injury to D or another? (2) D reasonably believed threat imminent? (3) No realistic escape/police protection? (4) Would sober person of reasonable firmness yield? Consider age, sex, disability, psychiatric conditions (Bowen)—not self-induced vulnerabilities. (5) Voluntary association bar? Objective test—D associated with criminals and ought to have foreseen risk.

Practical triggers: Self-defence: unprovoked attacks, defending others, preventing crime. Duress: gang threats, domestic abuse (though imminence problematic), organised crime coercion. Courts strictly apply Hasan—many duress claims fail on imminence or voluntary association.

Confusing defences: Self-defence applies against aggressors; duress when threatened by third party to commit crime against another. Different tests entirely.

Missing subjective element: Self-defence requires only honest belief in necessity—reasonableness goes to force used, not belief. Students wrongly assert 'unreasonable belief defeats defence'.

Duress availability: Never available for murder/attempted murder—discuss Howe before dismissing. Students forget voluntary association bar—if D joined gang foreseeing risk of compulsion, duress fails even if specific crime unforeseeable.

Intoxication: Mistaken belief due to voluntary intoxication cannot ground self-defence (s.76(5)). Critical in problem questions with drunk defendants.