General defences: insanity and automatism, intoxication (voluntary and involuntary, specific and basic intent), self-defence and the prevention of crime, and consent, with their requirements and effect on liability.

What this dot point is asking

This dot point covers the general defences in criminal law, which apply across offences. You need the requirements and effect of insanity and automatism, intoxication (voluntary and involuntary; specific and basic intent), self-defence and the prevention of crime, and consent. Some are complete defences (acquittal), some lead to a special verdict, and intoxication often only reduces liability. WJEC tests application to scenarios, advising whether a defence succeeds.

The answer

Insanity and automatism

Automatism is an involuntary act caused by an external factor (for example a blow to the head, or a reflex), where the mind is not controlling the body. It is a complete defence because it negates the voluntary actus reus. The key distinction from insanity is the internal/external cause: an internal cause (such as diabetes affecting the brain, R v Hennessy) points to insanity, while an external cause (such as an insulin injection, R v Quick) points to automatism.

Intoxication

Self-defence and consent

Self-defence (at common law) and the prevention of crime (section 3, Criminal Law Act 1967) form a single complete defence. The test has two limbs: (1) was the use of force necessary, judged on the facts as the defendant honestly believed them to be, even if mistaken (R v Gladstone Williams; R v Beckford), though a drunken mistake does not assist (R v O'Grady); and (2) was the force reasonable (proportionate) in the circumstances (R v Clegg; R v Martin). The Criminal Justice and Immigration Act 2008 confirms that a person acting in the heat of the moment cannot be expected to weigh the force to a nicety.

Consent is a defence to assault and battery, but generally not to offences causing actual bodily harm or worse (R v Brown), subject to recognised exceptions such as properly conducted sports, surgery, and tattooing.

Examples in context

The diabetes cases show the fine line between insanity and automatism. In R v Quick a diabetic who took insulin but failed to eat acted involuntarily because of an external factor, the insulin, so he could rely on automatism and was acquitted, whereas in R v Hennessy a diabetic whose high blood sugar resulted from failing to take insulin was treated as insane, because the cause (the disease itself) was internal. Intoxication then turns on the offence charged: in R v Lipman a defendant on LSD who killed his partner could not be convicted of murder, a specific intent offence, because his intoxication negated the intent, but he was guilty of manslaughter, the basic intent fallback. R v Kingston shows the limit of involuntary intoxication: a man whose drink was spiked but who still formed the intent to abuse a child remained liable, because the intoxication did not remove his mens rea.

Try this

Q1. State the two limbs of self-defence. [2 marks]

• Cue. Was force necessary (on the facts as the defendant believed them), and was the force reasonable (proportionate)?

Q2. Can voluntary intoxication be a defence to a basic intent offence? [2 marks]

• Cue. No: becoming voluntarily intoxicated is itself reckless, so it is no defence to a basic intent crime (DPP v Majewski).

Q3. Explain the general defences of insanity, intoxication and self-defence. [12 marks]

• What the marker wants. Insanity (M'Naghten and the special verdict), automatism (external cause), intoxication (voluntary/involuntary and specific/basic intent), and self-defence (necessity and proportionality), with cases and their effect.