Defences (Failure of Proof): Automatism vs Insanity

Question 1

Automatism v Insanity Overview

Answer 1

Intro - why, insanity (mnaghten rules), automatism (bratty)

Internal v External - hennesy v quick, ambiguity ( kemp & t)

Scope & Requirements - high v low (bratty, mnhagthen), eg. bailey, failures to defences(hill v baxter, windle), criticism (semester and sullivan)

legal social consequence - special verdict(bratty), full acquittal, unfairness three comparison, law commission

conclusion

Question 2

Intro (Automatism v Insanity)

Answer 2

“The distinction is not merely theoretical, but results in starkly different social and legal outcomes for defendants.” → this shows why comparison matters.

However, the categorisation of mental and physical conditions as internal or external leads to sharp distinctions in legal treatment. This essay will critically compare the two defences along key dimensions. In doing so, it will expose the incoherence and injustice in the current doctrinal divide.

Insanity
Definition: A defence where D was suffering from a mental condition that impaired their ability to understand what they were doing or that it was wrong.
M’Naghten Rules
Test for insanity
D must prove:
1. A defect of reason
2. Arising from a disease of the mind
3. Which caused D to either:
- Not know the nature and quality of the act, OR
- Not know the act was legally wrong

Automatism
definition of automatism “an act which is done by the muscles without any control by the mind” - Bratty v A-G
Lord Denning Hill V Baxter - swarm of bees
two ways:
(1) unable to control body
🚗Mitchell(1983) it was Mitchell who was deemed to be the cause of the elderly woman’s death rather than the man whom Mitchell caused to fall on top of her.
(2) subject to mental condition
🚗Quick - not eating and insulin shot

Question 3

Internal v External (Automatism v Insanity)

Answer 3

1. External v Internal Cause

🚗R v Quick – hypoglycaemia = external cause = automatism
Facts: A diabetic nurse assaulted a patient. He had taken insulin but had not eaten, causing hypoglycaemia.

🧠 Hennessy – hyperglycaemia = internal = insanity
The court held that hyperglycaemia caused by failure to take insulin is the result of an internal bodily condition (diabetes) — not an external factor — even if medicine was chosen not to be taken — individual rights

• Criticism → Arbitrary distinction → same underlying diabetic state → different results depending on cause.

2. Legal insanity ≠ medical insanity (kemp)

🧠 Kemp – disease of the mind (hardening of arteries)
A disease of the mind includes any condition that impairs mental faculties, even if it is not classed as a psychiatric illness medically. — internal can be physical

• Criticism → Legal concept ignores medical definitions → stigmatizing and outdated.

3. Internal due to external cause***

🚗 T PTSD Rape Case - Yes — the court accepted that severe psychological trauma caused by an external event (the rape) could constitute an external cause, thereby supporting a defence of automatism (not insanity).
ONLY if caused by extenal event - **

Overall issue: The internal/external distinction is artificial and results in inconsistent legal outcomes.

Question 4

Scope and Requirements (Automatism v Insanity)

Answer 4

1. High v Low Threshold

Automatism: Total loss of control (High Threshhold)
- Bratty → “Act done without control by the mind.”

Insanity: Cognitive incapacity or knowledge of wrongfulness (Low Threshold)
- M’Naghten → Must not know nature/quality or wrongfulness of act.

2. eg. Bailey → If self-induced and foreseeable → no defence.

🚗Bailey (1983)
1. Diabetic took insulin and didn’t eat → assaulted someone.
2. Court: if the defendant knows the risks of entering an automatism-like state, automatism might not apply.
3. but in r v quick, did not purposefully do so doesn’t apply
4. foresee? actually lose control?

3. Failures to defences (Wrongfulness vs Forgetfulness)

• Hill v Baxter → Mere forgetfulness ≠ automatism → must be total loss of control (e.g. bees, blow to head).
  forgot fell asleep and crashed car - dangerous driving
  acts of God like “swarm of bees” only.
  which break chain of causation
  complete loss of control
  The court held that mere lack of memory is not enough to prove automatism or involuntary conduct. There must be evidence of a complete loss of voluntary control caused by an external factor (e.g., being attacked by a swarm of bees, struck by a stone, or losing consciousness from a blow).
• Windle → “Suppose they’ll hang me” → knowledge → insanity defence failed.
  • Stupid but knowledge of wrong
    Windle – awareness of wrongfulness
    suicidal wife a fatal dose of aspirin. After her death, he said: “I suppose they’ll hang me for this.”
    awareness of wrongfulness is a key threshold
  4. Criticism:Automatism requires total loss of control (high threshold) while insanity focuses only on cognition. This produces unfair divergence: some with severe impairments may fail to qualify for either defence.
  As noted by Simester and Sullivan (2022), the law’s current approach treats insanity defendants with an outdated and stigmatising lens, while restricting automatism so narrowly that deserving defendants struggle to qualify.

Question 5

Legal and Social Consequences (Automatism v Insanity)

Answer 5

Insanity: Special Verdict and potential deprivation of liberty
- Verdict of “Not guilty by reason of insanity.”
As Lord Denning noted in Bratty, the special verdict reflects public protection concerns, but its use even in cases lacking moral blameworthiness results in harsher outcomes than automatism.
- Can result in hospitalisation, supervision, or detention (loss of liberty).

Automatism: Full acquittal
- If successful → D walks free without restrictions.

Criticism

This creates unfairness. Such disparity creates an arbitrary and unjust legal landscape.
1. A diabetic (Quick) who causes harm due to external trigger → acquitted. A diabetic (Hennessy) whose condition arises internally → stigmatized and potentially detained v Bailey (punished for trying)
2. Law Commission, 2013, expressed concern that the distinction between insanity and automatism produces inconsistent and stigmatising outcomes, particularly given that insanity attracts special verdicts and possible deprivation of liberty

Question 6

Conclusion (Automatism v Insanity)

Answer 6

Although insanity and automatism are both concerned with involuntary conduct, the sharp dichotomy between internal and external causes has resulted in incoherent and unjust legal distinctions. Insanity is outdated and overly narrow in its cognitive focus, while automatism is excessively restrictive with its requirement for total loss of control. Moreover, the disparity in outcomes — special verdict versus full acquittal — raises serious questions about fairness and consistency.

Given the inconsistency, stigma and harshness of current doctrines, reform towards a unified, medically-informed approach is increasingly essential to ensure criminal liability aligns with fairness and justice., so too must the law, towards a unified and fairer approach to involuntary actions in criminal liability.