The Insanity DefenceConflict and Reform in New Zealand

Abstract Relative to other jurisdictions, New Zealand’s experience with the insanity defence is brief. A statutory defence was first enacted in 1893, and its substance has changed little. In its development it has adhered closely to a narrow cognitive test of capacity, exclusive of emotional or volitional elements, and regardless of recent neuropsychological insights. Statutory changes, including the adoption of a standard of knowledge of moral, as opposed to legal wrong, mark a more inclusive insanity formulation, despite the small annual numbers of cases where insanity is pleaded. The introduction of a novel procedure for determining insanity by agreement in the absence of a trial, introduced in 2003, today accounts for the vast majority of successful insanity pleas in New Zealand, eliminating the distress and conflict of experts often associated with insanity trials. Unresolved judicial opinion, however, still remains around whether the insanity test requires proof of total incapacity as opposed to subjective lack of knowledge of wrong, potentially exposing defendants to the requirement of a higher threshold of capacity than the law seems to demand. Any significant change to the formulation of the insanity defence has been rejected by the New Zealand Law Commission. However, the advent of widespread methamphetamine abuse and associated legal issues have challenged the workability of the defence, questioning whether it remains fit for purpose. In addition, questions raised by the Convention on the Rights of Persons with Disabilities further challenge the appropriateness and viability of the defence and its conformity to international human rights norms.