1 The rules on insanity are based on the M'Naghten
1.1 M'NAGHTEN - D thought he was being
prosecuted by the Tories and tried to kill a
member of the Government. Because of his
mental state he was found not guilty of
1.1.1 This lead to the
House of Lords
184.108.40.206 DEFINITION: "D must have such a defect of reason, from a
disease of the mind which impairs his ability to understand the
nature and quality of the act he was doing or not know what he
was doing was wrong.
2 There are 3 elements that
need to be proved.
2.1 1. Defect of
2.1.1 D's power of reasoning must be
impaired. If D is capable of
reasoning but fails to use his
powers, then this is not a defect of
2.1.2 CLARKE - D took coffee and other items from the
supermarket and put them in her bag. She claimed she
forgot she had taken them from the shelves.
220.127.116.11 It was held that absent mindedness is not a defect of
reason and that insanity cannot be used as a
2.2 2. Disease of
2.2.1 The defect of reason must be due to a
disease of the mind. This is a legal term
not a medical one.
18.104.22.168 Disease of the mind can be
mental or physical.
22.214.171.124.1 KEMP - D had hardened arteries which
caused problems with the blood supply in the
brain causing temporary loss of
consciousness. D attacked his wife during an
unconscious episode, with a hammer. He was
found not guilty by reason of insanity.
126.96.36.199.2 SULLIVAN - House of Lords looked at whether
epilepsy came within the rules of insanity. D was
allowed the defence as it was held that it did not
matter if the impairment was permanent or transient
as long as it existed at the time of the act.
188.8.131.52.3 HENNESSY - D a diabetic didn't take his insulin and
had high blood sugar levels. During this time he stole a
car while being disqualified from driving. D was allowed
the defence of insanity as high blood sugar levels due
to the diabetes was affecting his mind .
184.108.40.206.4 BURGESS - In this case it was held that in some
instances sleep-walking was within the legal definition of
insanity. D attacked his girlfriend in his sleep and there was
no evidence of any external cause for the sleep-walking. D
was found not guilty by reason of insanity.
220.127.116.11 External factors - if D is in a state where
he is unaware of his conduct due to an
external cause the defence of insanity is
18.104.22.168.1 QUICK - D was a diabetic who had taken his insulin but not
eaten enough causing low blood sugar levels, which affects
the brain. D assaulted a person but it was held that this
condition did not come within the definition of insanity and it
was caused by an external matter (the insulin).
2.3 3. Causing D to be unaware
of the nature and quality of
2.3.1 There are two ways in which D may not know the
nature and quality of the act; because he is in a
state of unconsciousness or if he is conscious, but
due to his mental condition, does not know what he
is doing is legally wrong.
22.214.171.124 WINDLE - D's wife spoke of suicide so D killed her by giving her
100 aspirins. He gave himself up to the police and said "I suppose
they will hang me for this." He was suffering from a mental illness but
his words showed he was aware that what he had does was legally
wrong so could not use the defence of insanity and was convicted of
126.96.36.199.1 JOHNSON - D, a schizophrenic, stabbed his neighbour.
The courts followed the case of WINDLE and held that it
didn't matter if D didn't know what he was doing was morally
wrong because he was aware it was legally wrong.
Therefore, D couldn't use the defence of insanity.
3 The burden of proof of insanity is on the
defence, on a balance of probabilities.
3.1 If the defendant can use the defence of insanity
the verdict will be "not guilty by reason of
3.1.1 Insanity is not a defence to strict liabilities
but to all offences where mens rea is
188.8.131.52 Up until 1991 the judge had to send the defendant to a
mental hospital if found not guilty by reason of insanity.
This was clearly not suitable for all cases such as cases
of diabetes, epilepsy, etc. Therefore, the judge can now
impose a hospital order, supervision order or an
4.1 The definition of insanity is outdated as it was set out
by the M'Naghten Rules in 1843. Knowledge at this time
was limited on mental disorders so a modern definition
should be used.
4.1.1 A wider range of options has stopped injustice
for diabetics and epileptics, as previously the
judge had to send the defendant to a mental
hospital. Judges can now give them a
supervision order or even an absolute discharge.
4.2 The definition of insanity is a legal, not medical one, which
is causing issues. People suffering from mental disorders
cannot use the defence if they know their act is legally wrong
but may have irresistible impulses, like in BYRNE. Even
though they cannot prevent themselves from acting and have
a recognised mental disorder they cannot use the defence of
4.3 Social stigma comes with the word 'insanity' so is it fair to
be deeming those with physical disorders like epilepsy
and diabetes insane? This has led to defendants
pleading guilty to avoid the social stigma.
4.4 The burden of proof that D is insane is on him. It could be
argued this is a breach of the European Convention of Human
Rights which states the defendant is innocent until proven guilty.
4.5 The jury have to decide whether the defendant is
insane or not but is this appropriate? Shouldn't a
medical expert deal with matters where medical
evidence is used as it can be technical?