Allowing expert evidence that resulted in a conviction for a gangland slaying has been described as baffling and contradictory by an associate professor of law.

This month the Court of Appeal (COA), in a split decision, dismissed Damien Shane Kuru’s challenge to a jury’s November 2021 verdict, finding him guilty of the manslaughter of a rival Mongrel Mob member.

Associate Professor Carrie Leonetti, Auckland University Law School, believes the “expert evidence” relied on to convict Kuru has resulted in a miscarriage of justice and the Supreme Court needs to step in.

Kuru, president of the Whanganui chapter of Black Power, had been charged with Kevin Neihana Ratana’s murder after he was shot dead on the front lawn of a Castlecliff home in daylight on August 21, 2018.

The jury reached its manslaughter verdict after a six-week trial in the High Court at Wellington, despite no direct evidence linking Kuru to the killing.

Instead, the Crown’s case hinged on the trial testimony of police gang expert Detective Inspector Craig Scott.

“In my experience a [serious] organised gang crime against another gang would likely occur with the sanction of the president,” Scott told the jury during the trial, the COA decision detailed.

What jurors didn’t hear was Scott’s initial brief of evidence, a statement read in court, asserting the attack “would only occur with the sanction of the president” and the “president’s authorisation would be required”, after those passages were ruled inadmissible.

Kuru was sentenced to five years and two months imprisonment in February 2022 and has a statutory release date in December 2023.

Carrie Leonetti, an Associate Professor at the University of Auckland Law School said the evidence against Kuru was “legally insufficient” to satisfy a jury of his guilt.

Justice Helen Cull, in dissenting from the COA majority verdict, believed the testimony led the jury into “impermissible reasoning” through “bad person” prejudice, resulting in an unreasonable verdict and an unsafe conviction.

All three justices agreed that Scott’s evidence was admissible, but Leonetti told NZME profile evidence relating to gang practices was “highly problematic”.

“These cases allow juries to ‘infer’ that gang members engaged in particular conduct on a particular occasion because that is how most gang members are thought generally or typically to behave,” she said.

“That [Scott’s] evidence tells us exactly nothing about whether Kuru gave the order in this case.”

Leonetti, who teaches criminal law, evidence, psychiatry and the law, and miscarriages of justice, believed the testimony contained flawed reasoning and shouldn’t have gone before the jury.

“The fact that most of these hits have presidential approval is irrelevant to the question of whether this particular hit had presidential approval.”

She described the admission of the evidence regarding “typical” behaviour of gangs as baffling because the court has prohibited it in other contexts.

The ban included expert psychological evidence about how victims of child sexual abuse “typically” behaved, expert medical evidence relating to injuries in support of a rape complainant, and expert psychological evidence about the “typical” impacts of methamphetamine use on witness memory.

“In all situations, the court recognised that evidence about how a class of people ‘typically’ behave in a situation is logically irrelevant and even misleading for juries trying to determine how a particular person behaved on a particular occasion.”

Mongrel Mob member Kevin "Kastro" Ratana was shot dead in daylight on a residential Whanganui street in August 2018 by members of the Black Power because he was living on their turf.

The majority verdict ruled the jury “could have” reasonably inferred Kuru, as president, “would have” had knowledge of major activities of his members, “would have” known about the ongoing problems with Ratana, “would have been likely” to realise they were heading toward Ratana’s house, and “would also have” anticipated they were carrying weapons.

Leonetti said inferences were not “circumstantial evidence” but rather “pure conjecture” based on logical leaps from a police officer’s anecdotal experience.

“If the Court of Appeal is unwilling or unable to see why it is not a reliable basis for juries to base their decisions, the Supreme Court should step in and regulate it.”

Last year, the Supreme Court posthumously overturned Peter Ellis’ conviction, unanimously concluding the expert evidence - suggesting a shared set of behaviours between the complainants and children known to have been sexually abused - didn’t support the verdict.

She said the evidence against Kuru was “legally insufficient” to satisfy a jury of his guilt to the required standard of beyond a reasonable doubt.

“The prosecution did not have a shred of evidence connecting this defendant to the killing. But that would have been more obvious if the court had not admitted the inadmissible expert evidence in the first place.”

Kuru’s defence had an opinion piece from Dr Jarrod Gilbert, an expert on New Zealand gang culture, which broadly agreed with Scott, but strongly warned against overreliance on such beliefs when examining specific incidents.

Individual chapters operated differently and a gang’s internal politics could break down, events could happen quickly, without planning and the president may have little or no control over certain members or specific actions.

“The gangs certainly have a level of discipline and structure but ultimately they are made up of rebellious and difficult-to-control men.”

It was a mystery why Kuru’s defence did not call Gilbert as a witness, Leonetti said.

Defence lawyer Jamie Waugh said a further appeal to the Supreme Court was being considered.

Strategic decisions are made during a jury trial and because Scott’s evidence didn’t amount to proof beyond a reasonable doubt, Gilbert wasn’t called but in hindsight, the “illegitimate prejudice” attached to the title of “gang president” had been underestimated, Waugh said.

Six Black Power members were jailed for Ratana’s death but the shotgun used to fire the fatal round has never been found.

Gordon Runga was found guilty of manslaughter and sentenced to seven years’ jail and Anthony Kuru was sentenced to five years and three months’ imprisonment after pleading guilty to manslaughter.

Hikitia Rawiri Hakaraia, known as Hikitia Box, was jailed for nine years and seven months after pleading guilty to manslaughter and an unrelated killing in April 2018.

Sheldon Rogerson pleaded guilty to being party to murder and was sentenced to six years and four months’ jail while Damien Charles Fantham-Baker was imprisoned for five years and 10 months.

- Leighton Keith, Open Justice