Fang v R [2018] NSWCCA 210

Fang v R [2018] NSWCCA 210 · Read the judgment on AustLII

Catchwords: Defence of mental illness – whether drug-induced psychosis meets the common law test

The CCA has unanimously held that, at least on the evidence in this case, a drug-induced psychosis may not, on its own, meet the common law test for the defence of mental illness – although the Court also appears to have left the door open to reconsider the issue in a case where there is appropriate expert evidence.

The applicant stabbed the victim to death during the course of, or shortly after, a methamphetamine-fuelled argument. After the stabbing, he put the body in the boot of a car and, with tragic irony, left the car with its deceased passenger at a cemetery. A couple of days later he went to church and confessed. The pastor urged him to confess and he did that the next day: He went to the police and made admissions, although unfortunately it still took more than a week for them to find the car and its macabre contents. At trial, the applicant argued that he was suffering from a mental illness, such that he should be found not guilty by reason of mental illness. The question raised for the trial judge was whether drug-induced psychosis arising from the voluntary use of a prohibited drug may give rise to the defence of mental illness. That was set against a backdrop of a defendant who in this case had no history of mental illness, and who was assessed about three weeks after the offence but not diagnosed with a mental illness at that point, either. The trial judge ultimately determined not to leave the defence of mental illness to the jury, upon the basis that this was not a case where an existing mental illness was triggered or exacerbated by use of a prohibited drug. The jury ultimately convicted the appellant of murder. The only issue on appeal was whether the trial judge had erred by not leaving the defence of mental illness to the jury.

The court (Beazley P, RA Hulme and Button JJ, in a unanimous judgment) dismissed the appeal. The core issue about whether the drug-induced psychosis experienced by the appellant ought to have been left to the jury on a defence of mental illness hinged on the evidence about whether the drug use exacerbated an underlying mental illness or vulnerability. The question is whether there is a defect of reason resulting from ‘… an underlying pathological infirmity of the mind’ (at [88] to [89]). The difficulty which arises is whether a person in the defendants position suffered from a mental illness in the legal sense, or whether the person was acting under an external stimulus such as drugs or alcohol but was otherwise of sound mind (at [90]). Following a one line of reasoning (to the exclusion of a competing line), the court here seemed to endorse as a legal proposition that it is essential to the definition of a mental illness that it is ‘prone to recur’ (at [91] to [93]). And, whilst that view might need to be reconsidered at some stage having regard to the contemporary understanding of mental functioning, reconsideration would require evidence – and the evidence in this case did not allow for that departure (at [94]). The evidence in this case that some people who take drugs over a period of time might be vulnerable to developing psychosis was not sufficient to establishing a mental illness for the purpose of the common law defence (at [95] to [105]).