George Defteros, 63, was arrested on allegations he conspired with client Mario Condello to kill drug kingpin Carl Williams, his father George Williams and their bodyguard.

Mr Defteros told a court on Wednesday investigators advised him just before he was to be interviewed that charges may not proceed if he gave them information, particularly about Mr Gatto.

"In other words, if I was prepared to be a police informer, then they'd go easy on me and I'd possibly not be charged," Mr Defteros told the Victorian Supreme Court on Tuesday.

"I said I was not prepared to provide any such assistance."

The charges against Mr Defteros were eventually dropped in 2005.

A royal commission is now under way into how Victoria Police handles police informers, after revelations gangland lawyer Nicola Gobbo ratted on clients to help police secure convictions.

Mr Defteros was giving evidence in the Supreme Court, in a defamation trial against US-based Google.

The solicitor of 40 years - who has represented underworld figures, including Mr Gatto, Alphonse Gangitano and Graham "The Munster" Kinniburgh - says material about him continues to appear in Google searches that is damaging to his reputation.

Mr Defteros told the opening day of his trial he was "totally horrified" to see an article written in 2004 turn up in a Google search 12 years later, painting him as a friend and confidante of the underworld.

He said the searches revealed material alleging he was a criminal, part of a mafia conspiracy alongside gangland figures and had crossed the line from professional lawyer to become a player in the underworld.

"(It's) totally untrue and it has blackened my name," he said.

"There will be nothing that can ever replace my reputation or standing, certainly in the community generally and in some legal circles."

Mr Defteros said the false imputations caused him immense hurt and distress and prompted him to relive a "terrible" time in his life.

He told the court that after being charged, he was humiliated in court before his peers and had suffered bouts of depression.

He said family and friends deserted him, media and a gangland tour bus hung out outside his house, and he received death threats, including from Williams' ex-wife, Roberta Williams, and required 24-hour security.

"The place was like a fortress. We lived under siege conditions," he said.

"It was a really black period in my life.

"My whole professional career came to a crash."

An earlier bid by Mr Defteros to sue Google Australia over unflattering search results was thrown out by a Supreme Court judge in 2017, prompting him to pursue its US parent company.

Google will argue it only has control over the form, rather than the substance, of each web and image search.

Australian Associated Press