Introduction
The legal concept of "disease of the mind" is important in criminal law, particularly for defenses related to automatism and insanity. This concept determines when a person might not be held responsible for their actions due to a health problem altering their mental state. The 1957 case R v Kemp established a key principle by recognizing arteriosclerosis, a circulatory condition, as a potential "disease of the mind" in legal contexts. This ruling clarified how the concept applies to disorders affecting brain function, even through indirect means. The case showed how medical evidence informs decisions about legal responsibility and distinguished mental disorders from physical ailments.
The Facts of R v Kemp
The defendant, Mr. Kemp, struck his wife with a hammer while unaware of his actions. He suffered from arteriosclerosis, a hardening of arteries that restricts blood flow. In Kemp’s case, reduced blood flow to his brain led to a brief loss of consciousness and involuntary behavior. Medical evidence confirmed his condition and linked it to the assault.
The Legal Question
The central issue in R v Kemp was whether arteriosclerosis qualified as a "disease of the mind" under the M'Naghten Rules, the insanity test in England and Wales. The M'Naghten Rules require deciding if the defendant, due to a mental disorder, did not understand their act’s nature or wrongfulness. The defense argued Kemp’s physical condition altered his mental state enough to fit the legal definition of a "disease of the mind."
The Court’s Decision
The Court of Criminal Appeal upheld the trial judge’s finding that arteriosclerosis in this instance constituted a "disease of the mind." The court stressed that the key factor was the condition’s effect on mental function, not its physical origin. Lord Devlin stated that "the law looks at the result, not the source." Because arteriosclerosis impaired Kemp’s awareness and self-control, it met the legal criteria despite being a physical ailment. The court noted that the distinction depends on whether a condition disrupts mental processes, not whether it arises from physical or psychological causes.
The Impact of R v Kemp
R v Kemp reshaped judicial interpretation of "disease of the mind" by including conditions that indirectly impair mental function through physical mechanisms. This principle focused on mental consequences over medical origins. Later cases, such as R v Sullivan [1984] AC 156, followed this reasoning, allowing epilepsy to qualify as a "disease of the mind." R v Kemp ensured the law considers how conditions genuinely impair mental states, not merely their medical classification.
Comparing R v Kemp to Cases with External Causes
The R v Kemp principle contrasts with cases where external factors cause automatism. In R v Quick [1973] QB 910, a diabetic nurse assaulted a patient during hypoglycemia caused by insulin use. The court held this automatism stemmed from an external factor (insulin), not an internal mental disorder. This difference shows why identifying the cause of automatism is necessary for applying the "disease of the mind" principle.
Conclusion
The R v Kemp ruling remains central to interpreting "disease of the mind" in criminal law. The court confirmed that legal definitions must focus on mental impairment over medical origins. This approach has shaped later rulings on insanity defenses, helping courts address how health conditions affect accountability. The case shows the relationship between legal and medical analysis in judging criminal conduct. R v Kemp continues to influence judicial use of the M'Naghten Rules, ensuring legal standards stay relevant as medical knowledge grows. By focusing on actual mental impairment, the law maintains fairness when evaluating acts influenced by health issues.
