Automatism And Mental Disorder Defenses

🔍 Key Difference: Automatism vs. Insanity

Defence	Definition	Legal Consequence
Automatism	Acts done without voluntary control due to an external factor	Full acquittal
Insanity	Acts done due to a disease of the mind affecting reasoning ability	"Not guilty by reason of insanity" – may lead to hospital order or other outcomes

Facts:
Defendant strangled a girl during an epileptic seizure and claimed he had no control over his actions.

Judgment:
The House of Lords held that for automatism to succeed, there must be total loss of voluntary control.

Significance:
This case defined automatism and ruled that if the cause is internal (like epilepsy), it falls under insanity instead.

Facts:
A nurse assaulted a patient while suffering a hypoglycaemic episode (low blood sugar), caused by insulin treatment.

Judgment:
Court ruled this was automatism caused by an external factor (insulin), not insanity.

Significance:
Clear distinction: hypoglycaemia = automatism, because it results from medication, not the disease itself.

Facts:
Defendant committed robbery after a traumatic event (rape), and claimed it caused a dissociative state.

Judgment:
Trial judge allowed automatism to go to jury.

Significance:
Established that severe psychological trauma could — in exceptional cases — be treated as an external factor.

Facts:
Diabetic defendant failed to eat after insulin, leading to violent behaviour. Claimed automatism.

Judgment:
Court held that self-induced automatism may not be a defence if the risk was foreseeable.

Significance:
Introduced limitation: If D is reckless (e.g., failing to eat after insulin), automatism may not apply.

Facts:
Daniel M’Naghten shot and killed the Prime Minister’s secretary, thinking he was being persecuted.

Judgment:
House of Lords established the M'Naghten Rules, the foundation for the insanity defence.

M'Naghten Rules:

Defect of reason

From disease of the mind

So the defendant didn’t know the nature/quality of the act OR didn’t know it was wrong

Significance:
Still forms the legal test for insanity in UK law.

Facts:
Defendant attacked wife during a blackout caused by hardening of arteries affecting the brain.

Judgment:
Held to be insanity: medical cause was internal, affecting the mind.

Significance:
Clarified that “disease of the mind” can include physical illness affecting mental function.

Facts:
Epileptic seizure caused defendant to injure a neighbour. Defence of insanity raised.

Judgment:
Court held epilepsy = internal cause = insanity.

Significance:
Even temporary conditions can count as insanity if the cause is internal.

Facts:
Diabetic defendant failed to take insulin and committed an offence in a disoriented state.

Judgment:
Court held it was insanity (internal condition), not automatism.

Significance:
Distinguished from Quick – if the cause is the illness (not the treatment), it’s insanity.

Case Name	Defence Type	Key Principle
Bratty (1963)	Automatism	Defined automatism as total lack of control
Quick (1973)	Automatism	External factor (insulin) = automatism
T (1990)	Automatism	Trauma may be external factor
Bailey (1983)	Automatism	Self-induced automatism may be excluded
M’Naghten (1843)	Insanity	Created the legal test for insanity
Kemp (1957)	Insanity	Physical condition affecting mind = insanity
Sullivan (1984)	Insanity	Epilepsy = internal = insanity
Hennessy (1989)	Insanity	Illness (not treatment) = insanity