In 2007, Ms Gobbo was defending Rob Karam, who had been charged with importing five million ecstasy pills worth around $300 million, it was the largest seizure of the drug at the time.

Ms Gobbo was a junior barrister in Karam's trafficking trial by day, but by night she was gathering intelligence for police to use against her client over another drug import which was triple the size.

Karam was acquitted of the 2005 import but eventually locked up for 35 years over the failed 2007 attempt to import 15 million pills from Italy in food cans in what became known as the 'tomato tin' plot. That bust also led to the arrest and conviction of Griffith's Pasquale Barbaro, 57, who was later sentenced to life in prison.

An inquiry into police use of Ms Gobbo, known as 'Lawyer X', was told on Thursday that she had received a shipping cargo receipt from Karam during that trial which related to the upcoming import.

She asked if it would get her into trouble, and he replied "your fingerprints are already on (it)".

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Ms Gobbo had initially been told the container held tobacco, but Karam admitted it contained "bit of this, bit of that" when she confronted him about whether it was actually ecstasy or cocaine.

He later admitted it was 15 million pills. It took over as the world's largest haul when intercepted by federal police.

Ms Gobbo took copies of the documents and gave them to police, translating them from Italian for officers.

She had feared investigators outside Victoria Police might suspect her involvement as a co-conspirator rather than an informer. Australian Federal Police did suspect she was criminally involved, and told Karam after his arrest that she could not represent him because it would be a conflict of interest.

The inquiry was given damning evidence about the force's handling of Ms Gobbo, who continued to represent multiple clients whose criminal activities she had told police about.

- Australian Associated Press