What was determined to be a disease of the mind in R v. Hennessy (1989)?

In R v. Hennessy (1989), hyperglycaemia was determined to be a disease of the mind. This case involved a defendant who experienced a hyperglycaemic episode due to uncontrolled diabetes, which affected his mental state and led to the commission of an offense. The court established that hyperglycaemia could impair an individual's ability to understand their actions or to know that they were wrong, aligning it with the concept of a disease of the mind for the purposes of legal insanity.

The ruling emphasized the importance of distinguishing between mental diseases that can affect criminal responsibility and other factors that may not meet this standard. In this case, hyperglycaemia was not just a temporary condition but one that could result in lasting and profound effects on the mental state of the individual. This classification is crucial in determining liability under the defense of insanity in criminal law.