Police were still using Nicola Gobbo, the woman known as “Lawyer X”, as an informant for 19 months after she was deregistered as a confidential source, a royal commission has heard.

Gobbo, 46, was first registered as a police source in 1995, then again in 1999, and from September 2005 to January 2009, informing on a number of her own high-profile gangland clients, including Tony Mokbel.

Her identity was kept secret for five years during a lengthy legal battle between Victoria police and the Office of Public Prosecutions that went to the high court. It was finally revealed when a suppression order lifted last month.

The first public witness hearings of the royal commission into the management of police informants, established to examine how many criminal convictions may be undermined by Gobbo’s activities, began this week in Melbourne.

The terms of reference have already been expanded once because police did not tell the commission that Gobbo had first been registered as an informant in 1995, despite discovering that information in June 2018.

On Wednesday Chris Winneke, the council assisting commissioner Margaret McMurdo, said the police had since revealed they had continued to receive information from Gobbo until 27 August 2010, long after she had been deregistered.

Winneke said the relationship stopped after the then chief commissioner, Simon Overland, told staff not to receive information from her.

His ruling came after Gobbo had announced her intention to sue Overland and his predecessor, Christine Nixon, for failing to protect her over the role she played in the prosecution of corrupt former police officer Paul Dale.

Gobbo was a key witness in the prosecution of Dale for the murder of police informant Terence Hodson and his wife Christine but asked to be excused from giving evidence. The case subsequently fell apart and the charges were withdrawn in June 2010 – two months before Overland issued his instruction to staff.

The first person to give evidence before the inquiry, assistant commissioner Neil Paterson, told Winneke that he learned on 4 June 2018 that Gobbo had been registered as an informant in 1995.

The information was discovered when police, on his instruction, searched the archives looking for hard drives related to the case and found a hard-copy record.

That record noted that Gobbo’s reliability as a source was “very good” and that her motivation to be an informant was that she “genuinely wants to assist police.”

It further noted that Gobbo was “living with a known criminal,” a reference to an ex-partner with whom she was charged with drug offences following a raid on the house they shared in Carlton in 1993. It added that she was “quite reliable” and was seeking a career as a solicitor.

Gobbo admitted drug possession following the 1993 arrest but was not convicted while her partner pleaded guilty to and was convicted of drug trafficking.

In 1996, the commission heard, Gobbo provided information that was used to set up an undercover sting but the operation was pulled after then detective senior sergeant Jack Blayney, who later rose to the rank of assistant commissioner, noted that she was a “loose cannon.”

She was considered as an informant again in 1998, but an officer in that case said she should not be used because she was “too overt in her desire to provide information to police” and that “her relationship with some officers was inappropriate”.

Seven months later she was registered as an informer by the asset recovery squad in a fraud investigation focused on her then employer, a Melbourne law firm. Despite knowing she was then working as a solicitor, that application made no reference to her job.

Paterson said he did not tell the commission of the finding when it was established in December because legal action over Gobbo’s involvement had not stretched back that far.

“Based on my knowledge that the 1999 registration wasn’t relevant to those processes I didn’t place much significance on the 1995 process,” he said.

Winneke said that 35 of the 90 submissions received by the commission since January were from people who were concerned that criminal proceedings against them were now in doubt due to Gobbo’s role as a source. Three have already begun legal proceedings to challenge their criminal convictions.