• In the case of Hennessy 1989 2 All Er 9 it was held that the defendant was insane under the M’Naughten Rules and the defence of automatism was not available to him unless some external factor had affected his mental capacity.

Facts of the Case

  • D was charged with taking a motor vehicle without consent.
  • D suffered with diabetes and required to take insulin daily.
  • D, at the time of the incident was suffering with employment and marital problems that had been causing depression and stress.
  • D claimed he had not taken insulin for two or three days before the incident and as a result was suffering from hyperglycaemia.
  • D claimed that because of this, he was not aware of what he was doing, and the guilty mind could not be proven.
  • The judge at trial viewed that D was incapable of forming the necessary mens rea by reason of a disease of the mind so that he was insane within the meaning of the M’Naughten Rules.
  • D changed his plea to guilty and appealed against that ruling to avoid the label of insane.

Issues in Hennessy 1989 2 All Er 9

  • Could automatism be used as a defence of lacking mental capacity?

Held by Court of Appeal

  • Appeal dismissed.

Lord Lane LCJ

  • It was held that hyperglycaemia caused by high blood pressure sugar levels was an inherent defect that was a disease of the mind within the M’Naughten Rules.
  • The defence of automatism was not available unless D could show that his lack of mental capacity was due to an external factor.
  • “In our judgment, stress, anxiety and depression can no doubt be the result of the operation of external factors, but they are not, it seems to
    us, in themselves separately or together external factors of the kind capable in law of causing or contributing to a state of automatism. They D constitute a state of mind which is prone to recur. They lack the feature of novelty or accident, which is the basis of the distinction drawn by Lord Diplock in Reg. v. Sullivan [1984] A.C. 156, 172. It is contrary to the observations of Devlin J., to which we have just referred in Hill v. Baxter [1958] 1 Q.B. 277, 285. It does not, in our judgment, come within the scope of the exception of some external physical factor such as a blow on the head or the administration of an anaesthetic.

For those reasons we reject the arguments, able though they were, of Mr. Owen. It is not in those circumstances necessary for us to consider the further arguments which he addressed to us based upon the decision Reg. v. Bailey [1983] 1 W.L.R. 760.

In our judgment the reasoning and judgment of the circuit judge were correct. Accordingly this appeal must be dismissed. “ P.294