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Defences - Sleepwalking as a defence in Sexual Offence cases

Recent media reports have drawn attention to the successful use of sleepwalking as a defence, particularly in cases of rape and sexual assault.

It is essential that this defence is robustly challenged and a strategy to do so should be formulated as soon as it becomes clear that it is to be raised.

Sleepwalking is a form of automatism, and the normal principles in respect of the defence of automatism will apply:

  • First, a judge has to decide whether, as a matter of law, a proper evidential foundation has been raised for the defence to be put to the jury. This is likely to involve the defence adducing expert evidence:

    "I do not doubt that there are genuine cases of automatism, but I do not see how the layman can safely attempt, without the help of some medical or scientific evidence, to distinguish the genuine from the fraudulent" per Devlin J. in Hill v Baxter (1958) 1 Q.B. 277, 42 Cr. App. R. 51.

    Such evidence should always be analysed by an expert for the prosecution. If such evidence exists, the prosecution must exclude it as an explanation for what was done beyond reasonable doubt. This will necessitate proving that the defendants acts were voluntary in that they were committed when s/he was fully conscious.

    Prosecutors' attention is drawn to the persuasive authority of Finegan v Heywood The Times, May 10 2000, where the Scottish High Court of Justiciary held that automatism cannot be established as a defence upon proof of sleepwalking resulting from self-induced intoxication.
  • Secondly, the judge has to decide whether the evidence shows the case to be one of insane automatism within the M'Naghten Rules (that is, that the defendant was suffering from a disease of the mind), or one of non-insane automatism: R v Burgess 93 Cr. App. R. 41, CA. Medical evidence is a pre-requisite to a finding of insanity within the M'Naghten Rules.

    A finding of insane automatism will result in a special verdict of not guilty by reason of insanity. The defendant will then be made subject to a hospital order (with or without a restriction order), a supervision order, or an absolute discharge.

    A finding of non-insane automatism will result in a simple acquittal.

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