When can a defendant who has committed the actus reus and mens rea still avoid liability?
General defences in criminal law: insanity, automatism, intoxication, self-defence and prevention of crime, consent, duress and necessity.
A focused answer to the AQA A-Level Law criminal defences topic, covering insanity, automatism, intoxication, self-defence and prevention of crime, consent and duress, with the leading authorities for each.
Reviewed by: AI editorial process; not yet individually human-reviewed
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What this dot point is asking
AQA wants you to explain the general defences, state the legal test for each with a leading case, and identify which defence fits a scenario, including whether it is a complete or limited defence and which offences it covers.
Insanity and automatism
Intoxication
Self-defence, consent and duress
- Self-defence and prevention of crime are governed by the common law, section 3 of the Criminal Law Act 1967 and section 76 of the Criminal Justice and Immigration Act 2008. The force must be necessary (judged on the facts as the defendant honestly believed them, even if mistaken, R v Williams (Gladstone)) and reasonable and proportionate (R v Martin; householders have a slightly wider latitude).
- Consent is a defence to assault and battery, and to ABH or worse only in recognised exceptions such as properly conducted sport, surgery, tattooing and "rough horseplay"; it is not a defence to the deliberate infliction of actual or serious harm for sexual gratification (R v Brown) but was available in R v Wilson.
- Duress by threats requires a threat of death or serious injury directed at the defendant or someone close, such that a sober person of reasonable firmness would have acted as the defendant did (the two-stage test in R v Graham). It is no defence to murder or attempted murder (R v Howe, R v Gotts) and is lost if the defendant voluntarily joined a criminal gang (R v Hasan). Duress of circumstances and necessity operate on similar principles (R v Pommell, Re A (Conjoined Twins)).
Why the order of analysis matters
Examiners reward candidates who treat defences as the final stage, applied only after the offence is proved, and who distinguish complete defences (insanity, automatism, self-defence, duress) from the partial defences that belong with fatal offences. Naming the correct test and its leading case, then applying it to the named defendant, separates a top-band answer from a list of half-remembered rules.
Exam-style practice questions
Practice questions written in the style of AQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
AQA 201810 marksDev, woken suddenly and believing an intruder is attacking him, lashes out with a heavy torch and seriously injures his flatmate. Discuss whether Dev can rely on self-defence or any other general defence. [10 marks]Show worked answer →
Apply the law to Dev. Self-defence under section 76 Criminal Justice and Immigration Act 2008 has two limbs. First, was force necessary? This is judged on the facts as Dev honestly believed them, even if mistaken (R v Williams (Gladstone)), so his genuine belief in an intruder is the starting point. Second, was the force reasonable and proportionate in those circumstances? A single defensive blow may be proportionate; repeated or excessive force is not (R v Martin).
Consider automatism or insane automatism if Dev was not fully conscious on waking: an external cause supports non-insane automatism (R v Quick), while an internal sleep disorder points to insanity (R v Burgess). Markers reward identifying the correct defence, applying both self-defence limbs to Dev, and a reasoned conclusion on whether the defence succeeds.
AQA 20229 marksEvaluate the effectiveness of the law on the defence of intoxication. [9 marks]Show worked answer →
An Evaluate question needs balanced AO3 with examples. Strengths: the specific or basic intent distinction in DPP v Majewski protects the public by denying a defence to those who get voluntarily drunk and commit basic intent crimes, reflecting the policy that intoxication is itself reckless.
Criticisms: the distinction is arbitrary and not based on principle, R v Kingston shows a drunken intent is still an intent which can seem harsh on the involuntarily intoxicated, and the line between specific and basic intent offences is unclear. Markers reward developed points on both sides, accurate authority, and a supported conclusion on whether reform (for example the Law Commission proposals) is needed.
Related dot points
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A focused answer to the AQA A-Level Law fatal offences topic, covering the actus reus and mens rea of murder, the partial defences of loss of control and diminished responsibility, and unlawful act and gross negligence manslaughter.
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Sources & how we know this
- AQA A-level Law (7162) specification — AQA (2017)