The Lindsay Clancy case looks tragically like NZ’s Lauren Dickason trial. Here’s where they differ

After protracted deliberations, the jury in the Lindsay Clancy trial in Massachusetts has failed to

reach a verdict and the judge has declared a mistrial.

In a case that captured attention in the United States and around the world, Clancy had admitted killing her three children before trying to end her own life in 2023. She remains in hospital until a decision is made on whether there will be a retrial.

The prosecution argued it was a deliberate and calculated murder, evidenced by her arranging for her husband to be out of the house. That would likely lead to life imprisonment (as Massachusetts is not a death penalty state).

The defence argued she suffered a postpartum psychosis at the time and so was not in control of her actions. This should mean she is not guilty because she was insane at the time, or at worst guilty of manslaughter.

Maternal mental health was a focus of the trial and much of the wider public debate surrounding the case.

There are obvious factual similarities between the Clancy case and the Christchurch trial of Lauren Dickason in 2023. She also killed her three children when her husband was absent, and then took an overdose.

She was eventually found guilty of murder and given an 18-year prison sentence. An appeal will be heard in February next year.

The prosecution had argued it was a deliberate killing amounting to murder. The defence relied on mental health evidence about a major depression and argued for a verdict of not guilty due to insanity. But the defence also had an additional line to argue: infanticide.

The separate offence of infanticide

The infanticide option is a central difference between the criminal law in Massachusetts and in New Zealand – but also a number of other places, including Australia, Canada, and England and Wales.

Infanticide laws started as a way of avoiding a conviction for murder when the death penalty was still an available outcome.

The British parliament introduced an Infanticide Act in 1922 and then replaced it in 1938. Still in force, it allows the jury to convict a woman of infanticide rather than murder or manslaughter if she kills her child, the child is less than a year old, and a medico-legal test is met.

This test refers to whether “the balance of [the mother’s] mind was disturbed” from childbirth or lactation. The judge then sentences as if the accused is convicted of manslaughter, which need not involve a prison sentence. Similar provision is made for Northern Ireland in the Infanticide Act (Northern Ireland) 1939.

Infanticide laws spread to some other parts of the English-speaking world, though not the United States. Section 233 of the Canadian Criminal Code of 1985 has similar wording to the English law, except that it covers a “newly-born” child and the maximum sentence is five years.

Examples in Australia include section 6 of the Crimes Act 1958 in Victoria. This covers a child up to two years old and also has a maximum sentence of five years’ imprisonment.

In New South Wales, section 22A of the Crimes Act 1900 states infanticide involves a victim no more than 12 months old, but the medico-legal test has updated language. It refers to “a mental health impairment […] consequent on or exacerbated by giving birth to the child”. The woman convicted of infanticide is sentenced as for manslaughter.

In some other countries, there would also be an additional line of defence called “diminished responsibility” which leads to a manslaughter conviction. This is the case in Scotland, which does not have an infanticide law.

The idea of diminished responsibility is that, short of insanity, the law should recognise that mental health difficulties might play a role in killing that should be recognised by not labelling the person as a murderer.

These laws are wider than infanticide because they are not limited to women killing children.

New Zealand’s expanded infanticide law

Clearly, legislators have various ways of drafting the relevant language. New Zealand law reveals an independent streak.

It does not have the more general defence of diminished responsibility – this was rejected when the Crimes Act 1961 was being drafted. However, it has a much broader infanticide provision.

In the first place, it extends to a child under ten and is not limited to the child whose birth led to the relevant disorder. In addition, as the maximum sentence is a relatively low three years’ imprisonment, a prison sentence is less likely.

It still rests on a disturbed balance of the mind being caused by birth, lactation or a consequent disorder. The jury has to conclude the disorder is sufficiently bad that the woman is not fully responsible.

In the Lauren Dickason trial, she was convicted of murder. The jury concluded her depression did not meet the New Zealand test for insanity. They also rejected the partial defence of infanticide.

New Zealand law has an extra nuance. It allows judges to return to medical evidence at sentencing to ask whether a life sentence would be manifestly unjust despite the conviction for murder.

The presiding judge, Justice Mander, decided it was unjust in light of the mental health factors. The result was a sentence of 18 years’ imprisonment instead of life.

No one can doubt the criminal law should view with horror the deliberate killing of a child, including by a mother. At the same time, the criminal law should take into account the circumstances of the defendant, because criminal law is about moral fault, and that may vary.

Laws such as infanticide and diminished-responsibility manslaughter allow the jury to decide the level of fault.

Importantly, such laws should also be welcomed by those who prioritise accountability for a killing, even by someone who is mentally unwell. This is because they allow the jury to convict the mother of something, rather than find her not guilty.

The Lindsay Clancy trial illustrates how a jury can have difficulty when its choices are limited.

Kris Gledhill is a member of the Executive Committee of the Criminal Bar Association and is currently undertaking a criminal justice research project for the Borrin Foundation. The views expressed here are his own.