Underworld barrister Nicola Gobbo sent gangland kingpin Tony Mokbel an $84,000 legal bill at the same time she allegedly informed on him to police, a royal commission has been told.
Ms Gobbo - Melbourne's infamous 'Lawyer X' - also told one of her key police handlers that she had "chucked" all ethics out the window and would be in trouble if her true role was ever revealed.
The handler, known by the pseudonym Sandy White, told the royal commission into the police use of informers he wasn't aware Ms Gobbo sent the hefty bill to Mokbel in 2006.
However, he said on Monday the force believed at the time Ms Gobbo was compromised, would be murdered, and would bring "embarrassment and criticism" to the force.
"I've chucked ethics out the window, I've chucked legal privilege out the window, I've chucked my career out the window if any of this ever came out ... I would be so f***ed it's not funny," Ms Gobbo told Mr White in an audio recording played to the commission.
He added the barrister was motivated to inform as she wanted Mokbel, her legal client, out of her life.
Mr White also said she may have been motivated to inform on her clients in a bid to earn "brownie points" from police in case they ever tried to link her to serious crime, including murder.
Mr White also admitted Ms Gobbo was excluded from an investigation into allegations a police officer stole $20,000 while arresting one of her clients, as it was deemed "inappropriate".
However, he said in his dealings with Ms Gobbo, privileged information about her clients - information inadmissible in court - was "off the table".
"I don't think any of us thought a lawyer would be talking about privileged information," he said, before admitting Ms Gobbo had handed over such information from their first conversation in September 2005.
"She was compromised. We felt that she would be murdered," Mr White said.
"There would be a perception that we used her to obtain privileged information about her clients ... that would definitely embarrass Victoria Police."
Earlier on Monday Mr White said Ms Gobbo would regularly discuss confidential information while "venting", despite police "constantly advising" her not to.
"And it was not to be disseminated, that was the general rule," he said.
He said steps had been taken to hide her role as an informer from her clients and to use processes that protected her information from exposure in court subpoenas.
He also said Ms Gobbo was advised by police on a number of occasions not to take on clients due to a conflict of interest. However, that was her decision to make and she often ignored advice or engaged certain clients in a bid to "protect herself".
"Her greatest concern was she would be outed as a human source and she would be killed," Mr White said.
The hearing, before commissioner Margaret McMurdo, continues on Tuesday.