lc290 Partial Defences to Murder report - Law Commission

5.67 The second was:
Mitigation by reduced capacity: Where a person kills or is a party to
the killing of another, he shall be convicted of manslaughter and not
murder if at the time of the commission of the offence he was in an
abnormal state of mind which substantially impaired his ability to
appreciate the wrongness of his conduct, or his ability to act in
accordance with his recognition that his actions were wrong.
A person who would otherwise be guilty of murder is not guilty of
murder but is guilty of manslaughter if at the time of the act or
omission causing death:
(1) that person’s capacity to:
(i) understand events; or
(ii) judge whether that person’s actions were right or wrong; or
(iii) control himself;
(2) was substantially affected by a form of mental disorder as
defined in section 1 of the Mental Health Act 1983, which shall not
include any temporary alteration of mental state caused by drugs of
any kind; and
(3) the mental disorder was a substantial cause of the act or omission
causing death; and
(4) in the opinion of the jury, the mental disorder was an extenuating
circumstance, which ought to reduce the offence to manslaughter.
5.68 These versions have in common that they identify the link explaining why the
defendant’s culpability should be regarded as reduced by his or her mental
abnormality.
5.69 The second version has three ingredients which are not in the first version. One
ingredient is that “the mental disorder was an extenuating circumstance, which
ought to reduce the offence to manslaughter”. For the reasons that we have
already given, we are not attracted to that form of test. 77
5.70 Another difference is the stipulation that “the mental disorder was a substantial
cause of the act or omission causing death”, but we think that this difference may
be more apparent than real because we think that a causative link may be
regarded as implicit in the first version.
5.71 The most significant difference between the two versions is in the definition of
mental abnormality or disorder. The first version refers simply to an abnormal
state of mind; the second refers to a mental disorder as defined in section 1 of
77 See paras 5.54 – 5.56 above.
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