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The Defence of Automatism (WA)

Automatism refers to the involuntary conduct of a person caused by the lack of conscious volition. It includes actions or conduct such as:

  • Sleepwalking;
  • Episodes of epilepsy;
  • Dissociation caused by physical trauma such as a blow to the head, resulting in severe concussion;
  • Drug-induced psychosis; and/or
  • Psychological trauma or trauma resulting from extreme stress.

Sane automatism as a criminal defence

In Western Australia, Automatism is not a criminal defence in its own right. Automatism falls under the umbrella of the defence of unwilled conduct in Section 23 of the Criminal Code Act Compilation Act 1913. In the 1990 decision of Falconer, Justice Toohey stated that Section 23  “is wide enough to include automatism though it is not confined to that condition”.

For the prosecution to be successful in dismissing a claim of unwilled conduct (or sane automatism) the prosecution needs to prove beyond a reasonable doubt that the act of the accused was voluntary, and not involuntary. The appropriate verdict if a defence of automatism is raised and is successful is a full acquittal.

Psychological blow (or trauma-induced) automatism

There are a number of elements which must be met before psychologically induced automatism can fall under the umbrella of Section 23 of the Criminal Code. These are:

  • There must be external events which go towards constituting the trauma;
  • The automatism must be a transient occurrence that is not likely to recur in the future;
  • The trauma must be proven to be likely to affect a ‘reasonable person’ in a similar situation;
  • The trauma must be more severe than that of being subject to the everyday stressors that most people experience in life.

To prove that automatism was a result of psychological trauma the accused would need to allow the court to assess the severity of the trauma through a thorough consideration of all the circumstances. The common law cases of R v Falconer (1990) and Rabey v R [1980] allow the court to draw a distinction between what constitutes severe trauma and/or extreme stress triggering sane automatism and what does not.

R v Falconer

In R v Falconer the accused was in a state of dissociation, due to series of psychological blows, at the time of committing the relevant criminal act. The accused was subject to ongoing verbal and sexual abuse by the victim. At the time of committing the offence the accused was held to be in a state of dissociation and consequently did not remember the criminal act she committed. The court held that a new trial was to be ordered on the basis that psychological evidence should be led for the use of the defence of automatism.

Rabey v R

In Rabey v R the accused was a twenty-year-old student who was found guilty of causing bodily harm with intent to wound. The accused developed feelings for a classmate which were not reciprocated and as a result, he was hurt and angry. The accused attacked the other party grabbing her arms, choking her and striking her on the head with a rock he had taken from the geology lab, the day before. In this case, it was found that

“The ordinary stresses and disappointments of life which are the common lot of mankind do not constitute an external cause.”

The trauma of this male being rejected by a female, with whom he was infatuated, was not enough to satisfy the court that his psychological trauma was severe. Therefore, automatism was not found to be a viable defence the accused could use to justify his actions in harming the victim.

Insane automatism as a criminal defence

As well as automatism falling under the umbrella of unwilled conduct under s23 of the Criminal Code automatism is also closely related to the criminal defence of insanity under s 27 of the Criminal Code. Both insane automatism and insanity relate to a lack of conscious volition and combine this with an additional element of mental impairment. Both insanity and insane automatism are defences that are available to criminal acts such as murder or manslaughter. Where insane automatism can be proven the accused will be found not guilty due to mental impairment. The accused will not receive a full acquittal as occurs with a successful defence of automatism under Section 23.


The criminal defence of automatism falls into two distinct categories: sane automatism and insane automatism. Which category an accused’s defence of automatism falls into will determine the consequences of the defence being successfully raised. A successful defence under Section 23 will result in a full acquittal whereas a successful defence under Section 27 will lead to the accused being found not guilty by reason of mental impairment.

Whether a defence is successful will depend both on the circumstances of the offence and consideration of wider factors such as the criminal act committed and the extent of psychological trauma or other factors at play at the time the offence was committed.


Lisa Riley

Lisa Riley holds a Bachelor of Laws and a Graduate Diploma in Legal Practice. She also holds a Graduate Diploma in Counselling. She was admitted in the Supreme Court of Western Australia in 2018. During law school, Lisa wrote a parliamentary submission on Domestic Violence and received a personal response from the Premier, commending her on her willingness to advocate for vulnerable people. Lisa has experience in Personal Injury law, Workers Compensation, Will, Estates and Trusts and also has a keen interest in Mediation, Arbitration and Dispute Resolution.

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