A gangland killer had his jail sentence halved as a reward for turning on his underworld associates in a secret deal approved by the prosecutor, a Victorian inquiry into police informers has heard.
The crook, who cannot be identified, has told a royal commission his original 23-year maximum sentence for multiple murders was slashed through a petition for mercy.
Gangland-busting Purana Taskforce detective Stuart Bateson gave evidence in support of the man when he was originally sentenced for a series of murders.
The judge noted his assistance to police at the height of the underworld wars had been "very significant" and he was given a minimum 12-year non-parole period.
But the convicted killer, represented by lawyer turned informer Nicola Gobbo, revealed at the royal commission into her snitching on Monday that he had done a separate, secret deal with police and prosecutors.
His maximum sentence was reduced to 12 years and the non-parole period to just 11, though he served another 18 months or two years in the end, he said.
Assistance with his mercy petition was in lieu of rewards being offered for assisting in solving the murders, he told a closed court hearing.
"Geoff Horgan brought it up with Purana Taskforce," the man said of the now-retired senior crown prosecutor and QC.
"Once I finished giving all the evidence, that's when they (told) me that we're going to try to do this for you. Geoff Horgan said it. They tried and they got it for me."
Ms Gobbo's lawyer Rishi Nathwani pointed out that the man was at the top of the criminal tree but was a liar - and the man admitted it.
"You've dobbed on pretty much everyone," Mr Nathwani said.
"Same as your client," the man replied.
The man, a trusted underworld associate, claimed Ms Gobbo used him to get information.
He knew underworld murders were going to take place before they happened, and sometimes Ms Gobbo did too, he claimed.
"She knew that Jason Moran was going to get knocked. Because I told her. Everyone knew," the man said.
He said he came to suspect that Ms Gobbo was a police informer in the late 2000s. He'd been warned twice earlier but when he became convinced, he confronted her.
"Gobbo was pretty cocky because Gobbo knew after I rolled, I had no power to destroy her," he said.
"She tried to convince me that she wasn't, but she had a smirk on her face .. I'll never forget it."
He said he warned Gobbo that if it was true, her life would be at risk in the same way his was after becoming a witness.
"At the end of the day the underworld will find us all," he said.
The man's colourful evidence soured quickly in a heated exchange with Mr Nathwani, when the man threw out racist insults.
"You must not be offensive," Commissioner Margaret McMurdo shouted at the man in a rare display of anger.
"Thanks for the racist insult .. you need to grow up," Mr Nathwani added.