Legal Case Summary
R v Quick [1973] QB 910
Diabetes and defences – automatism or insanity in hypoglycaemia cases
Facts
The appellant (a nurse at a hospital) was a diabetic who suffered from hypoglycaemia (low blood sugar). He had taken insulin in the morning for his condition but had not eaten much during the day and had imbibed alcohol. This lead to an episode in which he blacked out and attacked his victim, who suffered black eyes, bruising and a fractured nose. He later passed out and denies any recollection of the events. At trial he was charged with assault occasioning Actual Bodily Harm contrary to s.47 Offences Against The Person Act 1861 and was convicted. He had attempted to rely on the defence of automatism, but the trial judge ruled that only the defence of insanity would be available.
Issues
On Appeal, the issue was whether a hypoglycaemia sufferer can rely on the defence of automatism or whether only the defence of insanity is available for this condition.
Decision / Outcome
It was held that a sufferer of hypoglycaemia can rely on the defence of automatism because the associated episodes (and the one in this case) are caused by the insulin (or lack thereof) which is an external factor, rather than by the diabetes, which is an internal factor. Therefore the conviction was quashed. No defence would be available for self-induced hypoglycaemia however. A sufferer of hyperglycaemia on the other hand would have to rely on the defence of insanity as episodes associated with that condition are caused by naturally occurring high blood pressure.
Updated 20 March 2026
This case summary remains broadly accurate as a statement of the law established in R v Quick [1973] QB 910. The core distinction drawn by the Court of Appeal — that hypoglycaemia caused by external factors (such as insulin) may ground a defence of automatism, whereas conditions arising from internal causes may only ground a defence of insanity under the M’Naghten rules — continues to represent good law and is regularly cited in criminal law teaching and in subsequent case law.
One factual inaccuracy in the article should be noted: the final sentence states that hyperglycaemia episodes are caused by ‘naturally occurring high blood pressure.’ This is incorrect — hyperglycaemia refers to high blood sugar (glucose), not blood pressure. The legal point being made (that hyperglycaemia arises from the disease itself, i.e. an internal cause, and therefore may only ground a defence of insanity) is accurate, but the description of the condition is wrong and could mislead readers.
The distinction between internal and external causes of automatism was further developed in R v Hennessy [1989] 1 WLR 287 (hyperglycaemia held to be an internal cause, supporting insanity rather than automatism) and R v Bailey [1983] 1 WLR 760 (self-induced automatism through failure to eat after taking insulin). These cases complement Quick and are worth reading alongside it. The Law Commission has at various points proposed reform of the automatism and insanity defences — most recently in its 2023 report on Automatism, Insanity and Cognitive Impairment — but no legislative reform has been enacted as of the date of this note, so the common law position in Quick remains in force.
