The Lawyer X royal commission has heard accusations a senior police officer deliberately misled a court to cover up the use of Nicola Gobbo as a human source.

Key points: A senior Victorian policeman has denied deliberately misleading a 2007 court hearing

A senior Victorian policeman has denied deliberately misleading a 2007 court hearing Inspector Dale Flynn had been giving evidence in a hearing involving associates of Tony Mokbel's drug ring

Inspector Dale Flynn had been giving evidence in a hearing involving associates of Tony Mokbel's drug ring He told the Lawyer X royal commission he believed his answers were truthful at the time

Inspector Dale Flynn, a former Purana taskforce detective, has been grilled about answers he gave under oath in the committal hearing for four of Tony Mokbel's associates who were facing drug charges.

One of the men, Zlate Cvetanovski, is now trying to overturn his conviction on the back of the Lawyer X scandal.

He is serving an 11-year prison sentence for commercial drug trafficking.

The group had been arrested along with Milad Mokbel in a raid on a drug laboratory in Rye on the Mornington Peninsula.

Police tactics to catch the criminals had involved the use of gangland lawyer-turned-police informer Nicola Gobbo, also known as Informant 3838.

She had convinced one member of the drug ring to turn against the others.

At a 2007 court hearing, Inspector Flynn was quizzed about that man's witness statement.

Under oath he had told the court it was "the one and only version that's been taken".

He also told the 2007 hearing there were no earlier drafts, and that while changes could have been made, there was no copy of them.

Tony Mokbel's brother Milad Mokbel had been unaware of Nicole Gobbo's role as a police informer. ( ABC News )

No 'intention to mislead'

But the Royal Commission into the Management of Police Informants heard evidence Inspector Flynn did know other copies existed and had been given to his colleagues and to Ms Gobbo.

Counsel assisting the royal commission Chris Winneke QC put to Inspector Flynn that his answer to the court had been misleading and had not been the whole truth as the oath required.

"I certainly wasn't intending to not give the whole truth," Inspector Flynn told the inquiry.

He said in answering the question, he had not given thought to the other statements or even known whether they still existed.

"It wasn't an intention to mislead" he said.

The inquiry heard the day the snitch was arrested, he called Ms Gobbo who then became instrumental in pushing him to become a witness against the Mokbel clan.

Ms Gobbo also visited the snitch when police did not believe he was telling the truth, and had discussed with her handlers what she thought should be in the statement.

"I suggest to you that you were not prepared to convey the full truth, the full sequence of events," Mr Winneke said.

But Inspector Flynn said his main objective was to try to conceal Ms Gobbo's role as a police informer.

He said he had thought Ms Gobbo was used to keep the key snitch happy and "on track", but conceded evidence before the inquiry had shown her role went much further.

Lawyer X had 'ethical bypass'

The main target of the police operation had been Milad Mokbel, a client of Ms Gobbo's who was unaware of her duplicitous role as a police informer.

The commission heard Purana investigators were aware she continued to involve herself in his case despite the "gross conflict".

Ms Gobbo spoke to her handlers about Milad Mokbel's jail conditions and was provided a brief of evidence to be used against him.

Inspector Flynn said any ethical conflict was matter for Ms Gobbo.

Mr Winneke said police should have intervened.

"She was not considering herself to be bound by any ethical constraints at all," Mr Winneke stated.

"She'd had an ethical bypass."

Inspector Flynn agreed police could have told her not to be involved and that senior police should have "thrashed it out" at the time.