Insanity

• Insanity is set out in the case of M'Naghten. It is defined as 'labouring under such a defect of reason, from a 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 he was doing what was wrong' .
• The burden of proof lies on the defence who must prove that the D was suffering from insanity at the time based on the balance of probabilities (M'Naghten). When D is found to be insane, the verdict is 'not guilty by reason of insanity'.
• Clarke


  D's power of reasoning must be impaired.
• Sullivan


  The defect of reason must be permanent or temporary.
• Burgess


  Disease of the mind is a legal term, not a medical one, and must be an internal cause.
• Kemp, Hennessy


  Can be a mental or physical disease which affects the mind. Can be temporary, as long as it is occurring at the time of the offence.
• Coley


  Voluntary intoxication is considered an external factor.
• Kemp, Sullivan, Hennessy, Burgess


  When the D is having delusions then they did not know the nature and quality of their act.
• Windle, Johnson


  'wrong' means legally not morally wrong.