Automatism as a Defence in Criminal Law

Introduction

Automatism describes actions carried out without conscious control. Because criminal liability usually requires a voluntary act, a defendant who acted in a state of automatism may have a complete defence. The standard is strict: there must be a total destruction of voluntary control at the relevant time, not merely reduced awareness or partial control.

Courts distinguish between two routes:

• Sane (non‑insane) automatism, caused by an external factor, which leads to a full acquittal.
• Insane automatism, caused by an internal condition or “disease of the mind”, which results in a special verdict of not guilty by reason of insanity.

Understanding where a case sits on this external–internal divide, how intoxication interacts with the defence, and what level of proof is needed, is essential for applying the law correctly.

What You’ll Learn

• What amounts to a total loss of voluntary control
• The difference between sane (external cause) and insane (internal cause) automatism
• How courts treat conditions like diabetes, epilepsy and sleepwalking
• The effect of intoxication and self‑induced states on the defence
• Key cases: AG’s Ref (No. 2 of 1992), Quick, Hennessy, Burgess, Sullivan, Kemp, Hill v Baxter, T, Antoniuk, Majewski, Hardie, Bailey
• How automatism compares with insanity and diminished responsibility
• Practical steps for raising and assessing the defence in problem questions

Core Concepts

Voluntariness and Total Loss of Control

Automatism negates the requirement of a voluntary act. The bar is high. In Attorney‑General’s Reference (No. 2 of 1992) [1994] QB 91, a lorry driver claimed “driving without awareness” after long, monotonous driving. The Court of Appeal held this was not automatism because he retained partial control and could have responded to significant stimuli. The test requires a total destruction of voluntary control.

Hill v Baxter [1958] 1 QB 277 reinforces the point: simple inattention, drowsiness or falling asleep at the wheel will not do. Courts look for proof of a complete loss of control caused by something outside the defendant’s own fault (for example, the classic hypothetical “swarm of bees”). Mere carelessness does not engage the defence.

Note on proof: for sane automatism, the defendant carries an evidential burden to raise the issue with some credible evidence. If the judge leaves it to the jury, the prosecution must prove voluntariness (i.e., disprove automatism) beyond reasonable doubt.

Sane vs Insane Automatism (External vs Internal Causes)

The external–internal distinction largely determines outcome:

• Sane automatism (external factor) → complete acquittal.
  R v Quick [1973] QB 910: hypoglycaemia caused by insulin and lack of food was treated as external; automatism was available.

• Insane automatism (internal factor; “disease of the mind”) → special verdict of not guilty by reason of insanity.
  R v Hennessy [1989] 2 All ER 9: hyperglycaemia from failure to take insulin was treated as internal; the proper route was insanity.

“Disease of the mind” is a legal concept, not a medical label. Courts ask whether the malfunctioning of the mind is due to an internal condition that may recur, impairing reason, memory or understanding, and requiring protection of the public.

Internal Conditions Treated as Insanity

Several conditions are treated as internal, so the insanity route applies:

• Sleepwalking: R v Burgess [1991] 2 QB 92 held that violent behaviour while sleepwalking stemmed from an internal condition that could recur. Insanity applied.

• Epilepsy: R v Sullivan [1984] AC 156 treated epilepsy as a disease of the mind, even though episodes are intermittent. The focus is on the impairment of mental faculties at the time, not the condition’s duration.

• Arteriosclerosis: R v Kemp [1957] 1 QB 399 held that a restriction of blood to the brain was a disease of the mind because it impaired reason, memory and understanding. The law protects the public where such impairments may recur.

Intoxication and Self‑Induced States

Where the loss of control is self‑induced, the defence narrows considerably.

• Voluntary intoxication by alcohol or dangerous drugs will usually block the defence for offences of basic intent: DPP v Majewski [1977] AC 443.

• Non‑dangerous drugs with unexpected effects can be different: R v Hardie [1985] 1 WLR 64 held that taking diazepam (Valium) is not like taking a dangerous drug. If the defendant did not know it might cause aggressive or unpredictable behaviour, automatism may still be open.

• Self‑induced automatism and diabetes: R v Bailey [1983] 1 WLR 760 states that if the state is induced without recklessness (e.g., a diabetic who omitted food after insulin without realising the risk of aggression), automatism may be available, including for basic intent offences. The key questions are:

  • Was the substance “dangerous” in the Majewski sense (known for causing unpredictability)?
  • Did the defendant appreciate the risk of losing self‑control or behaving aggressively and proceed anyway?

Automatism, Insanity and Diminished Responsibility: Key Differences

• Automatism: focuses on involuntary conduct. If the act was not voluntary, actus reus is not proved, and mens rea analysis may be unnecessary.

• Insanity (M’Naghten Rules): applies where a disease of the mind caused a defect of reason so the defendant did not know the nature and quality of the act, or did not know it was wrong. It results in a special verdict. R v Clarke [1972] 1 All ER 219 clarifies that mere absent‑mindedness or moments of confusion are not insanity; there must be a defect of reasoning power.

• Diminished responsibility (Homicide Act 1957 s.2, as substituted by Coroners and Justice Act 2009 s.52): partial defence to murder only, reducing murder to manslaughter where an abnormality of mental functioning substantially impaired the defendant’s responsibility. Unlike automatism, the act remains voluntary; the issue is reduced culpability.

Key Examples or Case Studies

• Attorney‑General’s Reference (No. 2 of 1992) [1994] QB 91
  Facts: Lorry driver claimed “driving without awareness” after monotonous driving.
  Held: Partial control is insufficient. The defence needs a total destruction of voluntary control.
  Use: Screens out reduced awareness or automatic driving responses.

• Hill v Baxter [1958] 1 QB 277
  Facts: Driver claimed to have blacked out.
  Held: Falling asleep, inattention or drowsiness does not amount to automatism. An external cause producing total loss of control is needed.
  Use: Sets limits; mere carelessness is not automatism.

• R v Quick [1973] QB 910
  Facts: Diabetic assault while hypoglycaemic after insulin and insufficient food.
  Held: External factor (insulin) → sane automatism possible.
  Use: Diabetes can be external (hypoglycaemia) if caused by medication/food issues.

• R v Hennessy [1989] 2 All ER 9
  Facts: Diabetic in hyperglycaemic state after failing to take insulin.
  Held: Internal condition → insanity.
  Use: Non‑compliance leading to internal metabolic state points to insanity.

• R v Burgess [1991] 2 QB 92
  Facts: Violence during sleep.
  Held: Sleep disorder treated as internal; insanity applies.
  Use: Sleepwalking‑related violence is usually classified as insanity.

• R v Sullivan [1984] AC 156
  Facts: Assault during an epileptic seizure.
  Held: Epilepsy is a disease of the mind; special verdict route.
  Use: Focuses on impairment of mental faculties at the time, not permanence.

• R v Kemp [1957] 1 QB 399
  Facts: Attack during a cerebral arteriosclerosis episode.
  Held: Disease of the mind because mental faculties were impaired.
  Use: The source is internal; legal label does not turn on medical terms.

• R v T [1990] Crim LR 256
  Facts: PTSD from a rape; dissociative state during robbery.
  Held: Trauma from rape could count as an external factor; automatism arguable if total loss shown.
  Use: Exceptional trauma may be treated as external on the facts.

• R v Antoniuk (1995) The Times, 28 March
  Facts: Shock following rape.
  Held: External factor recognised, but the defendant still had to prove total loss of control to raise the defence.
  Use: External cause alone is not enough; the total loss test remains.

• DPP v Majewski [1977] AC 443
  Facts: Offences committed while drunk or on drugs.
  Held: Voluntary intoxication is no defence to basic intent offences.
  Use: Blocks automatism where the state is self‑induced by alcohol or dangerous drugs.

• R v Hardie [1985] 1 WLR 64
  Facts: Took Valium, behaved unpredictably.
  Held: Non‑dangerous sedatives with unforeseen effects may allow automatism.
  Use: Ask whether the drug is “dangerous” and whether effects were expected.

• R v Bailey [1983] 1 WLR 760
  Facts: Diabetic failed to eat after insulin; subsequent aggression.
  Held: Self‑induced automatism can be a defence if the defendant was not reckless about the risk of unpredictable behaviour.
  Use: Nuances for diabetics; look at foresight of risk and type of offence.

• R v Clarke [1972] 1 All ER 219
  Facts: Depressed defendant shoplifted while absent‑minded.
  Held: Not insanity; no defect of reason.
  Use: Distinguishes confusion/absent‑mindedness from insanity.

Practical Applications

• Start with voluntariness: Identify the conduct and ask whether there was a total loss of control at the relevant time. If only partial control or reduced awareness, automatism fails.

• Pin down the cause:

  • External (e.g., blow to the head, medication effects, sudden trauma) → sane automatism.
  • Internal (e.g., epilepsy, sleep disorders, metabolic states from failure to medicate) → insanity.

• Diabetes checklist:

  • Hypoglycaemia after insulin or food imbalance → typically external (Quick).
  • Hyperglycaemia from missing insulin → typically internal (Hennessy).

• Intoxication filter:

  • Alcohol/dangerous drugs → Majewski blocks automatism for basic intent.
  • Non‑dangerous sedatives with unforeseen effects → Hardie may allow the defence.
  • Self‑induced states → Bailey: ask if the defendant foresaw or should have foreseen the risk of aggressive or uncontrolled behaviour.

• Proof and procedure:

  • Sane automatism: defendant must raise credible evidence; prosecution then must prove voluntariness beyond reasonable doubt.
  • Insanity: legal burden is on the defence on the balance of probabilities; special verdict possible, with disposal options including hospital orders.

• Exam or practice steps:

  1. Identify the act and timing.
  2. Determine whether control was totally lost.
  3. Classify the cause as external or internal.
  4. Apply intoxication rules if relevant.
  5. Match to offence type (basic vs specific intent) where self‑induced states arise.
  6. Conclude on defence availability and outcome (acquittal vs special verdict).

• Common pitfalls:

  • Treating drowsiness or lapse in attention as automatism.
  • Overlooking that sleepwalking and epilepsy are generally treated as insanity.
  • Ignoring the effect of self‑induced intoxication on basic intent offences.

Summary Checklist

• Total loss of voluntary control required (AG’s Ref (No. 2 of 1992))
• External cause → sane automatism; internal cause → insanity (Quick/Hennessy)
• Sleepwalking, epilepsy, arteriosclerosis → insanity route (Burgess, Sullivan, Kemp)
• Intoxication by alcohol/dangerous drugs blocks defence for basic intent (Majewski)
• Non‑dangerous sedatives may leave the defence open if effects were unforeseen (Hardie)
• Self‑induced automatism can still succeed if no recklessness (Bailey)
• Sane automatism: evidential burden on defence; prosecution must disprove
• Insanity: defence must prove on the balance of probabilities; special verdict applies
• Distinguish automatism from diminished responsibility (HA 1957 s.2; CJA 2009 s.52)

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