R v Hennessy

Facts

Hennessy was a diabetic. He took a car without the consent of the owner and drove it while disqualified. He said that he was in a state of automatism at the time because of hyperglycaemia, high blood sugar, which had been caused by his failure to take his insulin, in turn the result of stress, anxiety and depression.

History

At trial the judge ruled that the evidence raised the defence of insanity and not automatism. Hennessy then pleaded guilty to the charges and appealed against conviction to the Court of Appeal.

Issue

Whether a state of hyperglycaemia induced by the failure of a diabetic to take insulin was a disease of the mind within the McNaughton rules, so that the defence was insanity, or whether it was an external factor so that automatism was open.

Held

Appeal dismissed. Hyperglycaemia arising from diabetes was caused by an internal factor, the disease, and was a disease of the mind for the purposes of the insanity rules, so the judge was right to rule that it could not found a defence of non-insane automatism.

Ratio

• A disease of the mind in the legal sense is a disease which affects the mind, and the question is whether the malfunctioning of the mind is caused by an internal factor, such as a disease, or an external factor, such as a drug or a blow. If it arises from an internal factor, such as diabetes, the defence is insanity. Stress, anxiety and depression are not external factors for this purpose.

The judgments

Key reasoning

• The legal question is whether the state arose from a disease of the mind, the nature of which is determined by whether the cause is internal to the defendant or external to him.
• Hyperglycaemia is caused by the failure of the body to produce enough insulin and is therefore caused by the disease of diabetes, whereas hypoglycaemia caused by insulin is an external factor.
• Stress and similar psychological states are common experiences of life, and they are not external factors that can found a plea of non-insane automatism.

Where it fits in the module

In the Incapacity and General Defences topic the case demonstrates the legal definition of insanity and the consequences of classifying a condition as a disease of the mind. The module debates why a diabetic should be treated differently according to whether blood sugar is too high or too low, the unfairness of the special verdict, and the case for reform based on the Law Commission proposals. It should be read with Quick, Sullivan and Bratty.

Criticisms

• The internal and external division produces arbitrary results, since a diabetic who is in a state of automatism through too little insulin is treated differently from one who has taken too much, though the underlying condition is the same.
• The label of insanity for a physical condition such as diabetes is inappropriate and unfair, and it exposes the defendant to a special verdict and the risk of detention.
• The case treats the cause of the malfunction as decisive without explaining why the cause matters, when the real question should be the danger posed to the public and the blameworthiness of the defendant.