Recent work has highlighted the problem of amphetamine use in Queensland. In particular, concern has been expressed in relation to what has been described as a ‘disturbing trend’ towards the provision of exculpatory defences based on findings of ‘amphetamine‐induced psychosis’. While the subject of a spate of cases before the then Queensland Mental Health Tribunal, instances of drug induced psychosis are not restricted to Queensland. Similar issues have arisen in the context of the Victorian Law Reform Commission’s recent analysis of people with mentally impaired functioning who kill. What has become apparent in both case law and reform proposals dealing with this area is the interconnectedness of issues of principle and policy. The present article endeavours to clarify the thicket of conceptual and explanatory issues underlying voluntary drug use and the subsequent raising of a defence of non‐responsibility.