Mental Health Defences and Diversion

For less serious offences, a person experiencing a mental health impairment or cognitive impairment at the time of the offence may be eligible for diversion out of the traditional court process under the Mental Health and Cognitive Impairment Forensic Provisions Act 2020 (NSW). Rather than being dealt with in the usual way, the court can dismiss the charge on the condition that the person engage with appropriate treatment or support, without recording a criminal conviction.

This option is generally reserved for less serious matters, and the court must be satisfied it is more appropriate to deal with the person in this way having regard to the nature of their impairment, the circumstances of the offence, and any relevant treatment or support plan put before the court, often prepared with input from a treating psychiatrist or psychologist.

Separately from diversion, a person's mental or cognitive state can raise the question of whether they are fit to be tried at all — meaning whether they are able to understand the charge, follow the proceedings, and properly instruct a lawyer in their defence. Where fitness is genuinely in issue, this must be determined by a court process before the substantive charge can proceed.

If a person is found unfit to be tried, the matter does not simply end. Depending on the seriousness of the offence, the court may conduct a special hearing to determine whether the available evidence establishes that the person committed the offence, leading to orders directed at treatment and management rather than a conventional finding of guilt and sentence.

Where a person was suffering from a mental health impairment that meant they did not know the nature and quality of their actions, or did not know that what they were doing was wrong, this can support a defence of mental illness at trial. If successful, this generally results in a special verdict rather than an outright acquittal, and the court retains powers to make orders about the person's ongoing treatment and, in some cases, detention.

This is a complex area requiring expert psychiatric evidence and careful legal argument, and it is entirely separate from mental health being raised simply as a mitigating factor at sentencing for an offender who does not dispute their guilt.

Even where diversion or a defence is not available or appropriate, a genuine mental health condition can still be highly relevant to sentencing, potentially reducing moral culpability, explaining otherwise out-of-character conduct, or supporting an argument that a custodial sentence would weigh more heavily on the offender than on someone without the condition.

Supporting this argument properly requires clear, specific expert evidence — such as a report from a treating psychiatrist or psychologist — connecting the diagnosed condition to the offending itself, rather than a general assertion that the person has a mental health history.