Automatism Defence

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Automatism is the state of acting without being aware/without control over one's muscles. In other words, it is the denial that the actus reus was performed voluntarily. Automatism is argued as follows:

  1. There is a presumption against automatism. To raise the defence, the accused must satisfy an evidentiary burden that the action was performed in a state of automatism (ie, done involuntarily).
  2. The prosecution must then disprove automatism, (ie, prove voluntariness) beyond all reasonable doubt.
    • Automatism might be caused by a variety of factors:
      • A person with a sound mind who enters a dissociative state following some kind of trauma or a external 'psychological blow' will be considered as in a state of automatism and thus acting involuntarily: Falconer.
      • However, if the state of automatism was brought about because of a 'disease of the mind' or because the person had an unsound mind, then the act is still considered voluntary, but will be governed by the rules of the insanity defence (probably resulting a special verdict).
  3. If automatism is not disproved (ie, if voluntariness is not proved), than there is a missing actus reus element and therefore the golden thread is not satisfied. The accused will be acquitted because the offence was not made out.

Psychiatric evidence is often brought to examine automatism. However, psychiatric evidence of mental disease can only be brought to examine the issues of voluntariness if insanity is also brought up in the case: Hawkins. [1]

This article is a topic within the subject Criminal Laws.


Required Reading

Brown et al, Criminal Laws: Materials and Commentary on Criminal Law and Process in New South Wales, (5th edition, Federation Press, 2011), pp. 533-546.


[2] Automatism is when an act is done without the control of the mind (ie, an involuntary act). The automatism defence is based on the notion that a person should not be held guilty for actions done in an unconscious state. There are two types of automatism:

  1. Insane automatism - this is when the automatism was brought about because of a mental illness. It is not really automatism, but rather the insanity defence:
    • Involves satisfying the the M'Naghten test (and other common law principles) on the balance of probabilities.
    • Results in a 'special verdict' of 'not guilty by reason of mental illness' which may nevertheless still lead to long-term detainment.
  2. Sane automatism - this is when the automatism was not brought about by any mental illness but rather a simple issue of voluntariness (ie, a client arguing the automatism defence is simply arguing that his act was involuntary).
    • Involves the defendant raising the issue of voluntariness by satisfying an evidentiary burden. The Prosecution must then prove voluntariness beyond all reasonable doubt.
    • If the prosecution fails to prove voluntariness, than it failed to prove all the elements of the actus reus according to the 'golden thread', and there is no conviction. Thus, it is a full defence.
  • USG notes: the terminology is extremely confusing. It seems as though there is no need for the term 'automatism', since both insane and sane automatism are covered by the concepts of insanity and voluntariness respectively.


The procedure of how to argue the automatism defence (in particular, how to argue both insane and sane automatism) was discussed in case law.

Automatism was discussed in the UK in Bratty v Attorney-General for Northern Ireland:

  • When arguing that an act was involuntary, evidence needs to be brought for why the act was involuntary (evidentiary burden).
  • If the evidence only explains the 'involuntariness' by mental illness, than the issue is one of insane automatism, and thus the insanity defence, as opposed to sane automatism (voluntariness).

The leading case in Australia is Falconer:

  • There is a distinction between actions of a sound mind affected by an external psychological blow as opposed to those of an unsound mind ie, affected by a 'disease of the mind' as per M'Naghten's Case):
    • Actions of an unsound mind are still voluntary acts. They are, however, governed by the rules of the insanity defence and result in a special verdict.
    • Actions of a sound mind affected by an external psychological blow are not voluntary acts. Since there is no voluntariness, they will result in an outright acquittal.

The concept of a sound mind affected psychological blow as opposed to an unsound mind was also discussed in Woolbridge:

  • It is not for the psychiatrists to determine whether the accused was legally responsible for his/her actions - that is for the court. The psychiatrists' duty is to explain the mental condition of the accused.
  • A sound/sane mind would not go into a dissociative state from every small distressing experience. Rather, going into a dissociative state because of something which isn't that traumatic (ie, not enough to constitute a 'psychological blow)' can indicate that the accused actually has an unsound mind (thus subject to the rules of insanity).

[3] Note that psychiatric evidence of a mental illness cannot be brought to the jury unless the issue of insanity has been raised (ie, if no one raises insane automatism, psychiatric evidence can't be used for determining sane automatism/voluntariness alone).[4]

Causes of Automatism

There are a number of conditions which might cause a person to go into a state of automatism and thus act unconsciously/involuntarily. These include:

  • Dissociation - where, usually due to post-traumatic stress (or a psychological blow), a person may become detached from a situation and not act voluntarily.
    • In Donyadideh,[5] a previous extreme torture victim successfully argued that he went into a dissociative state once he saw the a symbol that was worn by his torturers.
  • Hypo/hyperglycemia - in some circumstances, sufferers of hypo/hyperglycemia who have injected insulin can be said to have acted involuntarily.[6]

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Textbook refers to Brown et al, Criminal Laws: Materials and Commentary on Criminal Law and Process in New South Wales, (5th edition, Federation Press, 2011).

  1. (1994) 179 CLR 500.
  2. Textbook, p. 532.
  3. Textbook, pp. 545-6.
  4. Hawkins (1994) 179 CLR 500.
  5. Unreported, FCA,2 August 1995.
  6. Quick and Paddison [1973] 1 QB 910.
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