Victoria Police has admitted the fact it paid a witness who gave evidence against drug kingpin Tony Mokbel might be "potentially relevant" to his appeal, but not enough to overturn any convictions.
Mokbel is appealing a series of convictions after the revelation his sometime lawyer Nicola Gobbo was a registered Victoria Police informer over two decades.
He has already had one conviction quashed because of the legal scandal, after commonwealth prosecutors conceded he'd suffered a substantial miscarriage of justice in one trial.
But separate convictions he is challenging are complicated by the fact Mokbel pleaded guilty in a deal that led to other charges being dropped.
In documents released on Wednesday, Victoria Police again conceded a witness - a drug cook known by the pseudonym Mr Cooper - who gave statements against Mokbel was paid by Victoria Police and Ms Gobbo.
Zlate Cvetanovski was acquitted by Victoria's Court of Appeal after police made the same concession in his case, but they say Mokbel's case is different.
In exchange for the cook's evidence Victoria Police was paying him $240-a-month into his prison canteen account, as well as a lump sum payment.
Between 2003 and 2012 he received almost $20,000. His evidence was used against more than 20 people.
While Mr Cooper was the principal witness against Mr Cvetanovski, lawyers for Victoria Police say he was only a "peripheral" witness in relation to Mokbel.
The force has also conceded it might be "potentially relevant" that they knew Ms Gobbo was giving legal advice to another man when she advised him to co-operate with officers.
He made statements and gave evidence against Mokbel in court.
They say it's possible that evidence could have been excluded if Mokbel went to trial because of the deliberateness of using a lawyer as an informer, and the gravity of any impropriety.
But they believe a judge would have found it more desirable to use the evidence, than to exclude it because any impropriety related to that witness and not to Mokbel, and it didn't affect the reliability of the witness' evidence.
Victoria Police has also argued that Mokbel hadn't pleaded guilty because of any improper inducement or fraud, but because he wanted to avoid the risk of being found guilty of additional charges, and "in the hope of obtaining a more lenient sentence".
His case is due back in court next year.