Raising a mental health defence or diversion in Australian criminal proceedings
Australian criminal law provides several pathways where mental health is relevant: the defence of mental impairment (not guilty by reason of mental impairment), unfitness to stand trial, substantial impairment of responsibility (for murder), and diversion from the criminal justice system under mental health legislation. Each state has its own statutory framework.
This is an 8-step workflow for assessing and raising a mental health defence (mental impairment, unfitness to stand trial, or substantial impairment) or seeking diversion under state mental health legislation in Australian criminal proceedings.
Before you start
- Client instructions or observations suggesting a mental health condition
- The brief of evidence or charge sheet
- Access to the client's mental health treatment records
- The applicable state mental health and criminal legislation identified
The workflow
Identify the relevant mental health pathway
Assess whether the case involves: (a) mental impairment at the time of the offence (defence), (b) unfitness to stand trial (capacity), (c) substantial impairment of responsibility (partial defence to murder), or (d) diversion under the Mental Health Act. The pathway determines the procedure and potential outcomes.
Obtain mental health records
Request the client's mental health treatment records from hospitals, psychiatrists, psychologists, and GPs. Obtain the client's informed consent for release. These records are critical for the forensic psychiatric assessment.
Brief a forensic psychiatrist
Engage a forensic psychiatrist experienced in criminal matters. Provide the brief of evidence, charge sheet, mental health records, and specific questions addressed to the relevant legal test (e.g. did the accused know the nature and quality of the act, or that it was wrong?).
Review the psychiatric report
Analyse the psychiatrist's opinion against the legal test in the applicable jurisdiction. In NSW, the test for mental health impairment is codified in the Mental Health and Cognitive Impairment Forensic Provisions Act 2020. Consider whether a second opinion is warranted.
Assess diversion as an alternative
Consider whether the matter is suitable for diversion under the state Mental Health Act or through a dedicated mental health court list (e.g. the NSW Mental Health Diversion Program, the Victorian Assessment and Referral Court). Diversion may be more appropriate for less serious charges.
Raise the issue with the court
File the appropriate application with the court. If raising unfitness to stand trial, the court will order a special hearing or inquiry. If raising the defence of mental impairment, serve the psychiatric report on the prosecution and notify the court of the intended defence.
Prepare for the hearing
Prepare the forensic psychiatrist to give oral evidence. For a mental impairment defence, the onus of proof is on the accused on the balance of probabilities. For unfitness, the issue is determined by the judge alone. Prepare submissions on the relevant legal principles.
Address the verdict and disposition
If the defence succeeds, the accused is found not guilty by reason of mental impairment. The court must then determine the disposition: unconditional release, conditional release, or detention in a mental health facility. Prepare submissions on the appropriate disposition, addressing community safety and the accused's treatment needs.
What you will have at the end
A determination on the mental health issue — acquittal by reason of mental impairment, a finding of unfitness, diversion from the criminal justice system, or the defence being rejected — with an appropriate disposition order.
Common issues
- Not obtaining mental health records early enough, delaying the forensic assessment
- Briefing a psychiatrist without the complete brief of evidence, producing an incomplete opinion
- Conflating unfitness to stand trial with the defence of mental impairment — they address different questions
- Not considering diversion for less serious matters where it may produce a better outcome for the client
- Failing to prepare for the disposition hearing, which determines whether the client is detained or released
Run this workflow on a real matter
Quillio identifies the relevant state mental health legislation, summarises the applicable legal tests, and helps structure the brief to the forensic psychiatrist. See /practice-areas/criminal-lawyers or start a free trial.
This workflow is a general guide. Mental health law in criminal proceedings varies significantly between jurisdictions — always verify the applicable Act and procedural requirements.
Try this workflow with Quillio.
Quillio can run this workflow on a real matter, with citations to current AU authority on every step. The free trial requires no credit card.
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