Michael Anthony Croke, 70, was found guilty in April of six charges including perverting the course of justice, aiding a criminal group and providing false or misleading statements to gain financial advantage.

In the NSW District Court on Thursday, Judge Helen Syme jailed the prostate cancer patient for five years and nine months with a non-parole period of three years and nine months.

The experienced Kings Cross solicitor had "an arrogant belief he was above the law," she said.

The foiled attempt to prove the money was legitimate began in August 2011 after police had a tip off about a gun at the Hilton but instead found the cash in a personal trainer's overnight bag.

Croke played a "pivotal" role in the plot which included cocaine importer Owen Hanson, a key witness at the solicitor's trial who is serving a long stint in a Californian jail.

He testified the money was part of the proceeds of illicit drugs and after its seizure he met Croke through a Sydney organised crime figure.

Concert promoter Andrew McManus was recruited into the conspiracy, telling the jury Croke coached him to provide a false story to police about the money being the proceeds of a Perth concert.

The solicitor sat in on the police interview when McManus, having previously ingested cocaine, ad-libbed with more details during his "enthusiastic" recounting of the story, the judge said.

"It seems objectively unlikely that the story that eventuated would be considered plausible, so outlandish were the claims," the judge said.

"Mr Croke was well aware that Hanson was involved in serious international criminal activity."

Over the course of three years, he used his legal knowledge and experience to subvert the police investigation and attempt to get the money back through the courts through a series of steps.

This included the preparation of false and misleading documents for the court proceedings.

"This offender gave directions and advice to guide and support the false story they had created," she said.

"The totality of his offending represents a serious assault on the system of justice in this state."

She expressed surprise that Croke was said to be "shattered" by his conviction, noting a solicitor of his experience would be well aware of that likelihood given the strong crown case.

She accepted he had good prospects of rehabilitation, referring to his age and the fact he wouldn't be practising law again.

Australian Associated Press