Top silk Bret Walker SC, who is also leading an inquiry into the Ruby Princess cruise ship, represented Comanchero outlaw motorcycle gang member Axel Sidaros at an appeal hearing on Thursday.

Sidaros, 25, is fighting the convictions that saw him handed a 14-year jail sentence for attempted murder and six other offences committed during a June 2018 shooting and arson attack. The victim was former Canberra Comanchero commander Peter Zdravkovic, who left the gang in a bitter fashion before losing a finger after being struck by a bullet in the attack.

Dramatic CCTV of the incident shows four hooded assailants on Zdravkovic's Calwell property, which they set ablaze. Sidaros, who rose from Comanchero nominee to patched member shortly after the incident, remains the only person to have been charged with carrying out the attack.

He was found guilty of seven charges at his trial but continues to claim he played no role in the incident, and on Thursday, Mr Walker said Sidaros' convictions should be quashed on multiple grounds.

Mr Walker told the ACT Court of Appeal that Chief Justice Helen Murrell should not have allowed the trial jury to hear evidence detailing "spontaneous utterances" Sidaros made to a police officer while being extradited to the ACT following his arrest.

Prosecutors relied on the detail of the comments during the trial in arguing that Sidaros had demonstrated a "consciousness of guilt" about the attack and lied to police.

But Mr Walker said the comments should have been excluded from evidence because the police officer acted improperly by giving Sidaros a document that contained a piece of false information, which had prompted Sidaros to speak.

Mr Walker further alleged that Chief Justice Murrell had given incorrect instructions to the jury on how to treat circumstantial evidence, with her approach potentially distracting and confusing jurors.

He said the judge had also made errors in directing the jury on how to approach the evidence of notoriously unreliable prison informers, whose testimony could be "easily concocted" for personal benefit.

Mr Walker said this was especially relevant in Chief Justice Murrell's instructions relating to claims made by jailhouse witness Zachary Froome, a criminal who received favourable treatment from authorities in exchange for his co-operation in the case. In a key aspect of Sidaros' trial, Froome said that Sidaros had confessed to the attempted assassination while on remand.

Mr Walker said Chief Justice Murrell's alleged errors had deprived Sidaros of "a real chance of acquittal".

"There should be a quashing of the verdicts and the convictions, and there should be an order for a retrial," Mr Walker said.

But ACT Director of Public Prosecutions Shane Drumgold SC told the court the appeal should be dismissed.

Mr Drumgold said police had made a legitimate mistake and did not knowingly provide Sidaros with false information. They had also reminded Sidaros of his right to silence twice before he made the comments Mr Walker described as "spontaneous utterances". The prosecutor said Chief Justice Murrell had been right to allow these comments into evidence at the trial.

Mr Drumgold also said Chief Justice Murrell had provided "comprehensive cautions" to the jury, and that Sidaros' appeal had failed to establish the possibility that jurors had been confused about how to deal with the evidence presented.

He said the jury had considered a wide variety of evidence and could have convicted Sidaros even without Froome's testimony.

The appeal court panel of Justice Michael Elkaim, Acting Justice Robert Crowe and Acting Justice David Robinson will hand down its decision at a later date.