Mental capacity defence. For insanity, D’s act is voluntary but they do not
understand the nature of the act or that it is legally wrong. D must prove on
the balance of probabilities that he was insane at the time of the offence, so
was unable to form MR.
DPP v H - insanity can only be a defence to an offence where it is necessary to
prove that D had the MR. If successful, D is not guilty by reason of insanity,
special verdict allowed under Criminal Procedure (Insanity and Unfitness to
Plead) Act 1991; this gives the court a range of options, hospital order,
supervision order, absolute discharge. In the case of murder, a hospital order
must be made restricting the D’s discharge indefinitly.
M’Naghten rules (1843): a person is presumed to be sane unless he was; 1.
Labouring under a defect of reason, 2. Due to a disease of the mind so that… 3.
They did not know the nature and quality of the act or he did not know that
what he was doing was wrong - if D doesn’t know because conduct was
involuntary, then it is insane automatism.
Defect of reason - requires a complete loss of the power of reasoning e.g.
thinking logically and drawing reasonable conclusions. Confusion or absent
mindedness is not a defect of reason (Clarke).
Disease of the mind - A legal term, not a medical one. Any disease which
produces a malfunctioning of the mind, the law is not just concerned with the
brain, but also mental faculties of reason, memory and understanding. E.g.
Kemp, Sullivan, Hennessey, Burgess.
Nature and quality of the act - two reasons why D may not understand: 1. D is
unconscious (an automatic state), insane automatism. 2. D is conscious but
due to their mental condition, does not understand the effects of their
conduct, insanity.
understand the nature of the act or that it is legally wrong. D must prove on
the balance of probabilities that he was insane at the time of the offence, so
was unable to form MR.
DPP v H - insanity can only be a defence to an offence where it is necessary to
prove that D had the MR. If successful, D is not guilty by reason of insanity,
special verdict allowed under Criminal Procedure (Insanity and Unfitness to
Plead) Act 1991; this gives the court a range of options, hospital order,
supervision order, absolute discharge. In the case of murder, a hospital order
must be made restricting the D’s discharge indefinitly.
M’Naghten rules (1843): a person is presumed to be sane unless he was; 1.
Labouring under a defect of reason, 2. Due to a disease of the mind so that… 3.
They did not know the nature and quality of the act or he did not know that
what he was doing was wrong - if D doesn’t know because conduct was
involuntary, then it is insane automatism.
Defect of reason - requires a complete loss of the power of reasoning e.g.
thinking logically and drawing reasonable conclusions. Confusion or absent
mindedness is not a defect of reason (Clarke).
Disease of the mind - A legal term, not a medical one. Any disease which
produces a malfunctioning of the mind, the law is not just concerned with the
brain, but also mental faculties of reason, memory and understanding. E.g.
Kemp, Sullivan, Hennessey, Burgess.
Nature and quality of the act - two reasons why D may not understand: 1. D is
unconscious (an automatic state), insane automatism. 2. D is conscious but
due to their mental condition, does not understand the effects of their
conduct, insanity.
