"(1) Where a person kills or is a party to the 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 a party to the killing. (2) On a charge of murder, it shall be for the defence to prove that the person charged is by virtue of this section not liable to be convicted of murder."
"A person ('D') who kills or is a party to the killing of another is not to be convicted of murder if D was suffering from an abnormality of mental functioning which - (a) arose from a recognised medical condition, (b) substantially impaired D's ability to do one or more of the things mentioned in subsection 1A, and (c) provides an explanation for D's acts and omissions in doing or being a party to the killing. (1A) Those things are - (a) to understand the nature of D's conduct; (b) to form a rational judgment; (c) to exercise self-control. (1B) For the purposes of subsection (1)(c), an abnormality of mental functioning provides an explanation for D's conduct if it causes, or is a significant contributory factor in causing, D to carry out that conduct."
"Indeed, given that in a fair proportion of cases, both defences are canvassed before the jury, the potential for uncertainty and confusion which would follow the necessarily very different directions on the issue of intoxication depending on which partial defence was under consideration, does not bear contemplation."
"The justifiability of any infringement of the presumption of innocence cannot be resolved by any rule of thumb, but on examination of all the facts and circumstances of the particular provision as applied in the particular case."
"Partial defence to murder: loss of control (1)Where a person ('D') kills or is a party to the killing of another ('V'), D is not to be convicted of murder if - (a) D's acts and omission in doing or being a party to the killing resulted from D's loss of self-control, (b) the loss of self-control had a qualifying trigger, and (c) a person of D's sex and age, with a normal degree of tolerance and self-restraint and in the circumstances of D, might have reacted in the same or in a similar way to D. (2) For the purposes of subsection (1)(a), it does not matter whether or not the loss of control was sudden. (3) In subsection (1)(c) the reference to 'the circumstances of D' is a reference to all of D's circumstances other than those whose only relevance to D's conduct is that they bear on D's general capacity for tolerance or self-restraint. (4) ... (5) On a charge of murder, if sufficient evidence is adduced to raise an issue with respect to the defence under subsection (1), the jury must assume that the defence is satisfied unless the prosecution proves beyond reasonable doubt that it is not. (6) ... (7) A person who, but for this section, would be liable to be convicted of murder is liable instead to be convicted of manslaughter. (8) ..."
"If and insofar as you conclude a personality disorder reduced his general capacity for tolerance and self-restraint, that would not be a relevant circumstance when you are considering the defence of loss of control. But it is important to emphasise that this exclusion only relates to any feature of a personality disorder which reduced his general capacity for tolerance and self-restraint. Let me give you an illustration. If you thought that CW suffered from a personality disorder which made him unusually likely to become angry and aggressive at the slightest provocation, that would of course be relevant to diminished responsibility but it could not assist him in relation to loss of control. But if you thought that a personality disorder had caused him to attempt suicide, then you would be entitled to take into account as one of his circumstances the effect on him of being taunted that he should have killed himself."