The Case for the Insanity Defence
Long-marginalised by scholars as her “drug dealer”, the man who was writer Robin Hyde’s constant companion for two and a half years — whose identity is only now being revealed — had to be something more.
The defence of insanity is a misunderstood and controversial area of criminal law that risks perpetuating misunderstandings around mental health, exacerbating existing bias in our justice system, and falling short of the responsibility of care for those who are impacted by it. It’s a two- pronged defence, requiring the jury to believe that the offender didn’t know what they were doing or didn’t know it was morally wrong.
Beyond sensationalised plot twists in TV crime procedurals, every so often it’ll also make the rounds in news headlines when it’s raised in a high- profile homicide case, such as the recent Lauren Dickason case.
It’s a slippery, murky corner of the law that began with compassionate foundations — an adjective not often associated with the justice system. Yet despite these high aspirations, its outdated definitions often perpetuate misunderstandings around mental health and reveal the failures in our institutions toward parties who find themselves in the justice system.
The defence is rarely successful as a special plea. The New Zealand Law Commission estimated that it was successful in 30-40 cases a year in New Zealand. More recent figures suggest an upward trend, as in 2023, around 56 people were found to be legally insane. Its tight formulation makes no allowance for the range of factors that may affect someone’s ability to make moral judgements or the variance in how this is expressed.
Warren Brookbanks is an internationally recognised expert in criminal law, and has written extensively on the defence of insanity, and how it stacks up against modern understandings of mental health. Because of the high threshold needed for the defence to be raised in court, it’s usually only brought up in homicide cases. And within that, only a small proportion of cases qualify for the ‘defence of insanity.’
Yet its black-and-white, sane or insane measuring stick doesn’t adequately align with a neuroscience- backed approach advocated by Brookbanks. He is also concerned by the rise in cases of offenders who may be experiencing psychosis or delusions, or lack the capacity to control their behaviour due to the consumption of substances like methamphetamine, yet are excluded from the insanity defence.
Despite the defence of insanity being raised in only a small percentage of cases, it’s important to take stock of how it reveals the archaic, clunky gaps of the justice system in its approach to those struggling with severe mental health. There’s a duty of care to be said and some hard questions to be asked on the positionality of incarceration and sentencing when compared to the general population, one in five New Zealanders will experience mental illness in their lifetime, while nine in ten of the incarcerated population have a lifetime diagnosis of mental health or substance use disorder.