Insanity, methamphetamine and psychiatric expertise in New Zealand courtrooms

The use of methamphetamine in New Zealand has increased significantly over the last decade. Due to the potential of methamphetamine to induce, exacerbate and precipitate psychotic symptoms, this drug has also taken centre stage in several criminal trials considering the sanity of defendants. Highly publicised and often involving contested expert evidence, these criminal trials have illustrated the limits of using psychiatric expertise to answer legal questions. This article considers the implications of such cases in light of material from a qualitative study that aimed to generate insights into the difficulties forensic psychiatrists and their instructing lawyers face when providing expert evidence on the relationship between methamphetamine, psychosis and insanity. It reports material from 31 in-depth interviews with lawyers and forensic psychiatrists and observation of one criminal trial that considered the relationship between methamphetamine and legal insanity. The findings are correlated with the clinical and medico-legal literature on the topic and subjected to scrutiny through the lens of "sanism". The article concludes that the continued use of forensic psychiatry to meet the legal objectives of insanity, where methamphetamine is involved, has the potential to reinforce sanist attitudes and practices.