Diminished reponsibility and intent

Should a person who has planned and carried out a murder be allowed to argue that a mental disorder had diminished his responsibility for the crime?

Interesting case from Singapore.

Is there anything similar from the courts in England & Wales?

I’m going to try to answer his one. I hope a criminal solicitor chips in now.

The test for the diminished responsibility partial defence to murder is in s2 Homicide Act 1957. It looks from the wording that the defence could potentially apply to a premeditated killing.

The guidelines on diminished responsibility in Sentencing Council, ‘Manslaughter: Definitive guideline’ (published 31/7/18, enforcement date 1/11/18) list “A significant degree of planning or premeditation” as a non-statutory aggravating factor increasing seriousness, and “Lack of premeditation” as a factor reducing seriousness or reflecting personal mitigation.

I haven’t been able to read the Singapore case so not quite sure what the particular legal point in contention is, but premeditation is not a barrier to a successful defence.

If you use this link to Twitter, the Secret Barrister has done a good thread after the Emily Jones killing where they explain the nature of the offence and it seems the prosecution argument for murder was precisely that the defendant planned the attack. As the thread explains, this doesn’t prevent the partial defence succeeding and as Jonathan has pointed out, the potential for planning and preparation is accounted for in sentencing guidelines. The only questions are those in the Act covering the defence, all of which can stand up with or without premeditation.

The barrister’s thread starts here - https://twitter.com/barristersecret/status/1334900002339086338?s=21&t=su10L4ucNEnkpwD2_Acktg


Jonathan has correctly used the word, “killing” instead of murder. So I think if the original poster substituted “murder” for “killing” the issue wouldn’t sound so outlandish. Thus, yes, anyone who has carried out a premeditated killing can run the partial defence of diminished responsibility. That said, the defence can only be run on a charge of murder simply because it is a defence specific only to a murder charge. If you think about it, in most of these cases the prosecution will be arguing the evidence shows there was ‘intention’ (‘premeditation’ in common parlance) to kill or to cause grievous bodily harm - whereas the defence will be raising diminished responsibility to explain his/her act. In practice anyway, the defence is only available upon expert evidence of the accused’s mental state.

The test, as Jonathan highlights, is set out at s2 Homicide Act. There are four main questions to be satisfied:

(1) Did the accused suffer from an abnormality of mental functioning?

(2) If so, did it arise from a recognised medical condition?

(3) If yes to (1) and (2), did it substantially impair one or more of the abilities listed in s 1A of s2 of the Homicide Act - that is, to understand the nature of his conduct; to form rational judgment and to exercise self control.

(4) If yes to (1), (2) and (3), did it cause or significantly contribute to his killing the deceased?

So it is one thing to raise the defence and quite another for it to succeed. Whether it does or no is largely a matter for the jury to determine.

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Intention and premeditation are two entirely different things, though - I can decide in a split second that I now intend to kill or seriously injure someone as I hurt them and if that unlawful act ends in their death, I’m still guilty murder even if there was zero premeditation (subject to any partial defence being successfully run of the kind we’re discussing here).

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