The killers of Tracey-Anne Harris were jailed after years of gossip and shaky evidence from drug underworld denizens, lawyers told the Court of Appeal today.
Rosana Mairo Morgan and Tyler Baillie were jailed for a minimum of 17 years for murdering Harris in Stoke, near Nelson.
But today, lawyers for Morgan and Baillie appealed against the convictions and sentences.
Justice Susan Thomas in 2019 said Morgan and Baillie were in a plot to kill Harris in exchange for money or drugs from the dead woman's aunt, Vicky Brookes.
A trial at the High Court in Nelson heard Brookes hated her niece so much, she had threatened to kill her and made a voodoo doll of her.
The trial judge said drugs were found in Harris' system, and when viewed in light of circumstantial evidence, were the results of attempts to induce an overdose.
But Ron Mansfield, appearing in Auckland today for Baillie, said the trial judge gave insufficient guidance to jurors about the quality of evidence from Crown witnesses.
And he disputed suggestions a "hot shot" containing a fatal methadone and methamphetamine mix was injected into Harris against her will.
Those two drugs and the psychoactive GHB were found in Harris' system after her death in February 2016.
"On the defence theory, she was a known drug user, had used drugs intravenously in that form," Mansfield said.
"She had voluntarily taken a drug which was too high in quantum and that had caused her death."
He said if Harris had not used drugs for a while, her tolerance may have weakened - so a previously survivable quantity might have proved fatal, even if taken willingly.
Mansfield said many trial witnesses were involved in drug use and to some extent, drug dealing.
He said one witness gave "entirely unreliable and incredible" evidence and some witnesses sided with Harris or had inducements to give evidence against Baillie.
"Juries require a more detailed direction than has been given."
Morgan and Baillie were convicted in Nelson on the basis Baillie suffocated Harris while Morgan assisted or encouraged the suffocation.
But Mansfield told the court there was no evidence of smothering if there was some force or struggle.
"What's important though, is that the evidence was the cause of her death was multiple drug toxicity," he added.
"All of the witnesses called by the Crown, the civilian witnesses, were part of the drug underworld," Morgan's lawyer Trudi Aickin said.
"The appellants were not arrested until two years after the death," she added.
Aickin said the Crown relied on incentivised witnesses making statements.
"A miscarriage of justice has happened because undue weight has been placed on unreliable, inconsistent evidence, incentivised evidence."
For the Crown, James Carruthers said the trial judge gave specific instructions about considering the evidence carefully.
He said the trial judge was correct to find the Crown drew on multiple strands of circumstantial evidence.
"The more strands you end up having to counter, the more difficult the task becomes to effectively neutralise them all."
Three people said Baillie had given them "rinse" or GHB in the lead-up to the murder.
The Court of Appeal reserved its decision, meaning it will make its decision on Baillie and Morgan's appeals at a later date.
Harris was 43 years old.