The ACT's top court has criticised the way police used undercover operatives to "defeat the rights" of a Comanchero bikie and extract a confession for the failed assassination of the gang's former Canberra chapter president.
An ACT Supreme Court jury found Axel Sidaros guilty in December of seven charges, including the attempted murder of Peter Zdravkovic, who lost the top of a finger in a June 2018 attack at his Calwell home.
Sidaros is the only person to have been charged with taking part in the attack, which involved four hooded assailants.
He was found guilty despite admissions he made to an undercover officer, in which he agreed he was "running the show", not being presented to the jury.
Court records show Sidaros did not consent to be interviewed after being brought to the ACT watch house following his arrest, and was placed in a cell with an undercover officer referred to as William.
William posed as a Sydney criminal arrested with "a bag full of cash", and as he probed for information, Sidaros expressed concern police might be recording, and even asked William if he was an undercover officer.
William tried to reassure him, saying police needed to "read you your rights or whatever before they do any of that shit", and that being an undercover cop would be "news to me".
Sidaros told William about siding against Zdravkovic during a split in the Comanchero gang, and said "a couple of the boys later on ... one night we went to the pres's house".
He agreed with William when asked if he was "running the show", and said he had been caught because he had used a gun registered in his name.
He also described local police as "shit c...." and said his co-offenders would not be caught because they had not used their own guns.
Sidaros also spoke to another undercover officer, referred to as Simon.
In August last year, ACT Supreme Court Justice David Mossop deemed the evidence collected by the undercover operatives to be admissible at Sidaros' trial.
But Sidaros appealed and Justice Mossop was overruled in November, shortly before the trial started, by the ACT Court of Appeal.
On Friday, the appeals court panel of Justice John Burns, Justice Michael Elkaim and Justice Chrissa Loukas-Karlsson revealed why it made the decision to keep the evidence from the jury.
The panel's judgment says there was a real danger convictions based on this evidence would have come at a price that was "unacceptable having regard to prevailing community standards".
The judgment says after Sidaros' lawyer told police at the watch house that he did not consent to be interviewed, police made a deliberate decision to "defeat [Sidaros'] rights" not to speak to officers.
Sidaros "obviously had no opportunity to walk away" from the undercover operatives because he was in the cells, the judges said, and he was not cautioned by these officers that what he said may be used against him in court.
"The context in which the deception occurred, and the combination of these factors, leads to exclusion [of the evidence] in this case," the judges said.
Sidaros is yet to be sentenced for the crimes he was convicted of in December.