Quick v Prettejohn [1973] QB 910

Facts

  • Raymond Quick, a diabetic nurse at a mental health facility, assaulted a patient.
  • Quick claimed he acted during a hypoglycemic episode resulting from taking insulin but failing to eat enough.
  • At trial, the judge directed the jury to consider insanity, leading to a special verdict of "not guilty by reason of insanity."
  • Quick appealed, contending that his actions were caused by external factors (insulin administration and lack of food), not a "disease of the mind."

Issues

  1. Whether hypoglycemia induced by insulin and lack of food constitutes an external factor or a "disease of the mind" for the purposes of criminal law defences.
  2. Whether the trial judge was correct in instructing the jury to consider insanity rather than automatism as the applicable defence.

Decision

  • The Court of Appeal held that Quick’s hypoglycemic state was caused by an external factor—insulin and lack of food—comparable to effects from head injuries or anesthesia.
  • The court determined that the appropriate defence in such circumstances was automatism, not insanity.
  • The judge’s direction to the jury to treat the episode as insanity was incorrect.

Legal Principles

  • "Disease of the mind" encompasses conditions affecting mental function, whether physical or psychological, but excludes states caused solely by external agents such as drugs, alcohol, or physical harm, unless revealing a pre-existing internal condition.
  • Automatism caused by external factors removes the actus reus and leads to a full acquittal.
  • Automatism with an internal cause classified as "disease of the mind" results in a special insanity verdict.
  • The defendant bears the initial burden to present sufficient evidence supporting a claim of automatism, usually requiring medical evaluation to determine the cause.

Conclusion

Quick v Prettejohn clarified the distinction between automatism resulting from external factors and that linked to a "disease of the mind." The decision established that automatism from an external cause supports a complete defence, while internal causes invoke insanity, shaping subsequent case law on mental capacity and criminal responsibility.

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