One of three men jailed for torturing and murdering two Queensland drug dealers whose bodies were found in a toolbox has appealed his convictions claiming the jury relied on inadmissible evidence.
Tuhirangi-Thomas Tahiata, then 28, was found guilty by a Brisbane Supreme Court jury in February 2020 of the murder of Cory Breton, 28, and Iuliana Triscaru, 31, and sentenced to life in prison.
Breton and Triscaru's bodies were found submerged in a lagoon south of Brisbane in February 2016.
Justice Peter Davis at the time described the killings as horrendous and said Tahiata played no role in beating and restraining the pair but he knew he was "driving them to their deaths".
The Brisbane Court of Appeal on Wednesday heard submissions on whether Tahiata's convictions should be overturned.
Tahiata's barrister April Freeman said there had been a error of law during the trial because the jury were told Tahiata had confessed to police while their interview video camera was switched off.
A police officer testified to the jury that Tahiata said: "I did it. I killed them. I murdered both of them."
The specific words Tahiata used during the confession were later ruled inadmissible as they were not an acceptable record under legislation governing Queensland Police conduct.
Freeman said the quote from Tahiata was presented to jury members as a "pivotal moment" in the trial.
"It affected the jury when looking at (Tahiata's) other police interviews and deciding which version is true," Freeman said.
The crown prosecutor said the inadmissible evidence was not material to the outcome of the trial and the error had not affected the jury.
"There was no complaint about it by (Tahiata's defence) counsel at trial ... it's a matter for the jury which version of events they accepted," the prosecutor said.
The prosecutor said there was other evidence that led to Tahiata's conviction including him saying "I committed murder, I'll face up to that" in a recorded interview with police.
Chief Justice Helen Bowskill, Justice Peter Flanagan and Acting Justice Michael Buss reserved their decision on the appeal.
© AAP 2023