Crimes Mental Impairment consultation paper.pdf - Victorian Law ...

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The test for establishing the defence of mental impairment
Knowledge about the nature and quality of the act
5.73 The requirement that the accused person not know the nature and quality of the act
refers only to the ‘physical character of the act’. 68
5.74 The High Court has described this requirement as a person’s ‘capacity to comprehend the
significance of the act of killing and of the acts by means of which it was done’. 69
5.75 In simple terms, a person will not know the nature and quality of their conduct if because
of a mental impairment they do not know ‘the physical thing [they were] doing and its
consequences’. 70 This statement implies that the knowledge of the accused person relates
to more than just the physical act:
In R v Porter, the common-law requirement of an accused’s lack of knowledge of
the nature and quality of an act has been interpreted as consisting of both a lack of
knowledge of the surface features of the act and its harmful consequences. 71
5.76 For example, a person who hits another person with a stick, but thinks they were actually
hitting a tree, would not know the nature and quality of their conduct.
5.77 The circumstances in which an accused person does not know the nature and quality of
their conduct are rare. The defence of mental impairment is most successful where the
second limb of the M’Naghten test is established. This limb relates to the way in which
the person processes knowledge about the nature and quality of their conduct and that it
was wrong. 72
Knowledge that the conduct was wrong
5.78 In Australia, the test for determining whether a person ‘knew what he or she was doing
was wrong’ is a moral one rather than a legal one. 73 It is about a person’s ability to
understand right from wrong.
5.79 The standard to be applied to the conduct is that of the ordinary person, ‘in the sense
that [an] ordinary reasonable ... [person] understand[s] right and wrong and that [as a
result of a mental impairment] he was disabled from considering with some degree of
composure and reason what he was doing and its wrongness’. 74
5.80 A causal relationship is required between the mental condition and a person being unable
to understand that their conduct was wrong. 75 This means that it must be because of the
person’s mental impairment that they did not know that their conduct was wrong:
[I]f the disease or mental derangement so governs the faculties that it is impossible for the
party accused to reason with some moderate degree of calmness in relation to the moral
quality of what he is doing, he is prevented from knowing that what he does is wrong. 76
68 R v Codere (1917) 12 Cr App R 21.
69 Sodeman v R (1936) 55 CLR 192.
70 R v Porter (1933) 55 CLR 182, 189.
71 Yannoulidis, above n 50, 15 (citation omitted).
72 Ibid 16.
73 Stapleton v R (1952) 86 CLR 358.
74 R v Porter (1933) 55 CLR 182, 190.
75 Ibid 189.
76 Sodeman v R (1936) 55 CLR 192, 215.
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