Methamphetamine, psychosis and criminal responsibility: rethinking the mental impairment defence

The increasing prevalence of methamphetamine use and its strong association with psychosis is placing significant pressure on legal doctrines of criminal responsibility. Laws governing intoxication and insanity were developed in an era of limited drug use and are ill-equipped to address the complex issues that now arise at the intersection of substance use, mental illness and offending. This article examines how Australian jurisdictions currently navigate this intersection. It argues that they rely on imperfect proxies, such as ‘disease’ and ‘intoxication’, to make an evaluative judgement about whether the accused is sufficiently blameworthy for causing their lack of capacity that they should be held criminally responsible. The article proposes that a blameworthiness-based framework, which directly addresses this question, would offer a more principled alternative. It argues that such an approach provides a clearer, fairer and more coherent basis for resolving these increasingly common and difficult cases.