A man has successfully appealed his conviction for the theft of a Ducati after arguing that prejudicial material was introduced at his trial.

Ricardo Romanov was convicted last year after a jury retrial again found him guilty of pinching a limited-edition $130,000 motorcycle in 2013.

It was the mention of his criminal past and multiple aliases during the retrial that has been deemed to have carried "considerable" prejudicial weight by Justices Christian Whata, Simon France and Murray Gilbert who have granted his appeal.

Under the guise of Anthony Ricardo Sannd or variations of that name, Romanov had already gained notoriety for stealing a Tissot masterpiece worth about $8 million from the Auckland Art Gallery in 1998.

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In the 2017 Ducati theft retrial the Crown alleged the burglary was carried out by Romanov and an accomplice, who testified for the prosecution.

The prosecution also showed the jury Romanov's computer searches to find the bike, DNA evidence left at the crime scene and the discovery of a key at his flat that could start the bike.

The defence argued it was the accomplice who had acted alone and was motivated by a personal dislike for Romanov to set him up with his testimony.

During the retrial several witnesses, including Romanov himself, made reference to either time he had spent in custody or in prison.

One police officer also revealed he had nine or 10 aliases and another witness revealed Romanov had already been sentenced to seven years' imprisonment during the first trial.

The Judge presiding over the retrial told the jury it was "vital that you put that material to one side".

On giving the Court of Appeal decision Justice France said the right to a fair trial had been irretrievably damaged.

"Our assessment is that the Judge did all that he could, but the circumstances were such that Mr Romanov's right to a fair hearing was irretrievably damaged," he said.

"As noted this was itself a retrial, and Mr Romanov has now spent over four years in custody in relation to this charge.

"The Crown responsibly did not seek a retrial direction and accordingly we make none."

Romanov's conviction was quashed by the decision.