legalEASE.
In the Criminal Law of England and Wales, there are a couple ways a person can deny liability by saying they were acting involuntarily at the time the crime was committed. These are separated into 2 broad groups; internal factors and external factors. The external factor group is concerned with saying a person acted involuntarily because they consumed a dangerous drug (alcohol or other drugs) or because of some other external cause. To deny liability as a result of an external factor one would look to the rules to intoxication or automatism. The internal factor group is concerned with some internal cause which meant the person acted involuntarily because of it; to deny liability in this scenario one would look to the defence of insanity.
This post is about the defence of insanity.
The M’Naghten Case (1843) sets out the requirements which must be met for a person to be eligible to use the defence of insanity.
The person must have been suffering of a “defect of reason”
This does not include just absentmindedness (R v Clarke [1972])
This relates to the person not having the capacity to reason at the time of the event
The person must be suffering of this defect of reason because of a “disease of the mind”
It does not matter whether the condition is “curable or incurable” or “transitory or permanent”, it just must be persisting at the time of the event (R v Kemp [1957])
While people may tend to think of mental disorders as “diseases of the mind” - it should be made very clear that the law does not recognise “disease of the mind” and “mental disorder” to mean the same thing
To meet this requirement “disease of the mind” is about mental faculties of reason, understanding and memory
For example: in R v Hennessy [1989], a diabetic man fails to take his insulin and enters hyperglycaemic state. His inability to understand what was happening around him, caused by his hyperglycaemic state, led to him stealing a car. The hyperglycemia was an internal factor because it was a result of diabetes, so he was eligible to use the defence of insanity.
The person must “not know the nature and quality of the act he was doing” or, even if they knew what they were doing, they must have not known “what he was doing was wrong"
Option 1: the person must not have known what he was doing
For example: if someone strangled another person but they believed they were juicing a lemon
Option 2: the person did not know what he was doing was wrong
In England and Wales, it must be proven that the person did not know the act was legally wrong and did not know it was morally wrong (R v Keal [2022])
To learn about intoxication see: Intoxication - not the defence you think it is!