Psychiatric defences

Psychiatric defences
· a defence can be made that the person is not culpable because he did not have a
sufficient degree of mens rea due to:
1. not guilty by reason of insanity
2. diminished responsibility (not guilty of murder, but guilty of manslaughter,
which requires a lesser degree of criminal intent
3. incapacity to form an intent because of an automatism
4. if a mother kills her child in the first year of life, she is not usually held
legally responsible for murder, but for the lesser charge of infanticide
Not guilty by reason of insanity
· embodied in the McNaghten rules (in 1842 Daniel McNaghten, a wood turner from
Glasgow, shot and killed Edward Drummond, private secretary to the Prime
Minister, Sir Robert Peel)
· To establish a defence on the ground of insanity, it must be clearly proved
that, at the time of committing the act, the party accused was labouring
under such a defect of reason, from disease of the mind, as not to know the
nature and quality of the act he was doing, or, if he did know it, that he did
not know what he was doing was wrong
· the McNaghten rules due not apply in Scotland
· the burden of proof lies with the defence
· based on the opinions on 2 psychiatrists ‘on the balance of probability’
· it counts as an acquittal, but the disposal is as Insanity in bar of trial
Diminished responsibility
· the defence of diminished responsibility for murder was introduced in 1957
· the Homicide Act 1957 (Section 2) states:
· where a person kills or is party to a killing of another, he shall not be
convicted of murder if he was suffering from such abnormality of mind
(whether arising from a condition of arrested or retarded development of
mind or any inherent causes or induced by disease or injury) as substantially
impaired his mental responsibility for his acts and omissions in doing or
being party to the killing
· if the plea is acceptable to the judge and prosecution, there is no trial but a hearing
and a sentence of manslaughter (culpable homicide) is passed
· it refers only to sentencing, not responsibility for the act in terms of guilt
· “degrees of mental illness produce degrees of culpability”
· personality disorder is not sufficient in Scottish Law
Culpable homicide
· there is a lack of specific or evil intent to kill
· Involuntary culpable homicide – an unintended death occurs as a result of an
assault or other criminal act or as a result of culpable negligence
· Voluntary culpable homicide – death results from an intentional reckless act but
because of provocation or diminished responsibility, the offence is reduced from
murder to culpable homicide