What is the Defence of Insanity in Western Australia?
Under Western Australian law, a person may not be held criminally responsible for their actions if, at the time of the offence, they were suffering from a significant mental impairment that deprived them of their ability to understand, control, or assess the wrongfulness of their conduct.
This is referred to as the defence of insanity, as outlined in Section 27 of the Criminal Code (WA):
A person is not criminally responsible for an act or omission on account of unsoundness of mind if at the time of doing the act or making the omission he is in such a state of mental impairment as to deprive him of capacity to understand what he is doing, or of capacity to control his actions, or of capacity to know that he ought not to do the act or make the omission.
This means that if an accused person was in such a state of mental impairment that they:
- Did not understand their actions,
- Could not control their actions, or
- Did not realise their actions were wrong,
they may not be held criminally liable for the offence.
Delusions and Criminal Responsibility
A distinction is made for individuals who suffer from delusions but do not meet the full criteria for the insanity defence. Section 27(2) of the Criminal Code (WA) provides:
A person whose mind, at the time of his doing or omitting to do an act, is affected by delusions on some specific matter or matters, but who is not otherwise entitled to the benefit of subsection (1), is criminally responsible for the act or omission to the same extent as if the real state of things had been such as he was induced by the delusions to believe to exist.
This means that if a person commits an offence while under a delusion, they may still be held criminally responsible unless their delusion was so severe that it rendered them incapable of understanding, controlling, or assessing the wrongfulness of their actions.
Defence of Insanity vs Unfitness for Trial
The defence of insanity and fitness to stand trial are two separate legal concepts, though they can sometimes overlap when mental impairment is an issue.
The defence of insanity focuses on the accused’s mental state at the time of the alleged offence—whether they were so impaired that they could not understand, control, or recognise the wrongfulness of their actions.
In contrast, fitness for trial concerns the accused’s mental capacity at the time of the court proceedings—whether they are able to understand the charges, instruct their lawyer, and meaningfully participate in their defence.
A person may have been legally insane at the time of the offence but regain sufficient mental capacity to stand trial. Conversely, an individual may not meet the legal criteria for insanity but still be deemed unfit to stand trial due to a severe deterioration in their mental condition.
If the accused is fit to stand trial but was not of sound mind at the time of the alleged offence, the defence of insanity may be considered.
Criteria for Fitness to Stand Trial
Under Section 9 of the Criminal Law (Mentally Impaired Accused) Act 1996, an accused is considered unfit to stand trial if, due to mental impairment, they are unable to:
- Understand the charge against them,
- Comprehend the need to enter a plea or its consequences,
- Grasp the purpose of the trial,
- Exercise their right to challenge jurors,
- Follow court proceedings,
- Understand key prosecution evidence, or
- Properly defend themselves.
If any of these factors apply, the accused may be deemed unfit for trial under Western Australian law.
Typically, the court will request a psychiatric evaluation to assess the individual’s fitness before proceeding.
Raising the Defence of Insanity
In Western Australia, every accused person is presumed to be of sound mind under Section 26 of the Criminal Code (WA).
If the defence seeks to rely on insanity, they must prove—on the balance of probabilities—that the accused was not of sound mind at the time of the alleged offence.
Whether an accused qualifies for the defence of insanity under Section 27 is a question of fact, determined only after all evidence has been presented in court.
What Happens When You Raise the Defence of Insanity?
If the defence of insanity is successfully established, the accused is acquitted of the offence. However, this does not mean they are free to go.
If the court finds that the accused was of unsound mind but that the elements of the offence were proven, they may be subject to orders under the Criminal Law (Mentally Impaired Accused) Act 1996 (WA). This can include lengthy or even indefinite detention in a psychiatric facility, depending on the circumstances of the case.
Misconceptions About the Defence of Insanity
A common misconception is that claiming insanity allows an accused to avoid responsibility for their actions. In reality, this defence does not mean the person simply “gets off the charge.”
Invoking insanity requires extensive psychiatric evaluations, and the legal threshold for proving a mental impairment is exceptionally high. If the court accepts the defence, the accused is not acquitted in the usual sense—instead, they may be detained in a psychiatric facility indefinitely, often for a period longer than a standard criminal sentence.
The court’s powers in cases involving insanity are governed by the Criminal Law (Mentally Impaired Accused) Act 1996 (WA).
Case Review: R v Porter (1933) 55 CLR 182
This case examines the defence of insanity in criminal law, focusing on whether severe mental impairment can absolve an accused of criminal responsibility. It highlights the legal standards for insanity and how courts assess claims of unsound mind.
Background
- Charge: Porter was charged with the murder of his infant son.
- Defence Argument: Porter claimed he was suffering from severe mental distress at the time, making him unable to control his actions or understand their wrongfulness.
- Key Context:
- Porter had recently experienced a mental and emotional breakdown following the breakdown of his marriage.
- Witnesses described him as deeply depressed, exhausted, and mentally unstable, having suffered from severe sleeplessness and agitation in the days leading up to the incident.
- Medical experts testified that his mental state had deteriorated to the point where he was incapable of rational thought or voluntary control of his actions.
- The defence argued that due to his disordered mind, Porter lacked the capacity to understand the nature of his actions, control them, or know they were wrong—meeting the criteria for insanity under the law.
Court’s Findings
The High Court of Australia ruled in favour of Porter, finding that:
- Insanity requires total deprivation of understanding, control, or moral awareness at the time of the offence.
- Porter’s mental state was so impaired that he could not be held criminally responsible.
- He was acquitted on the grounds of insanity, but this did not mean immediate freedom—he remained subject to mental health laws.
Legal Principles Highlighted
This case clarified key aspects of the defence of insanity:
- Severe Mental Impairment Required: Emotional distress alone is not enough; the accused must lack capacity to understand or control their actions.
- Strict Legal Test: Insanity is a high bar—defendants must prove complete mental incapacity at the time of the offence.
- Potential for Indefinite Detention: An insanity acquittal does not mean freedom; the accused may be detained under mental health laws.
The R v Porter decision remains a leading case in Australian criminal law, shaping how courts assess mental impairment in criminal responsibility.
**Please Note**
The material provided here is for informational use only and does not constitute binding legal advice. You should not use this information as a replacement for an individual consultation with a trained legal professional.
