It is a legal saga that risks destroying the career of high-profile Sydney lawyer Leigh Johnson, supporters say.

But the Woollahra solicitor has won support from an unusual quarter, with the son of the 80-year-old woman battling Ms Johnson in court speaking out against his mother to "put the record straight".

Fairfax Media revealed on Monday Ms Johnson is the subject of a scathing judgment in the NSW Supreme Court about the circumstances in which she agreed to take a 32.5 per cent stake in the Australian Institute of Music, the nation's largest private music school, from two elderly clients.

Justice Patricia Bergin, the chief judge in the court's equity division, said last year Ms Johnson had engaged in "inappropriate tactics" in her dealings with the founders of AIM, the late Peter Calvo and his wife Athalie, over the transfer of shares in the company. Justice Bergin struck down the transfer.

But the couple's eldest son and the former managing director of AIM, Daniel Paul Calvo, told Fairfax Media the result would have been very different if he had given evidence in the case.

"I'm forced to come forward now as originally I didn't take the stand. I didn't want to go up against my mother [in court]," Mr Calvo said.

He said his mother was not "a distressed elderly lady" and was "always sharp of mind".

"I can no longer sit back and watch Leigh Johnson's career being destroyed," he said.

Ms Johnson had been portrayed as a "monster, which is completely inaccurate".

"I'm ready to do whatever it takes now to put the record straight," he said.

Mr Calvo, who intends to bring legal proceedings against his mother over his father's estate, said Ms Johnson was "always promised" a parcel of shares in AIM for her work on a case to claw back shares in the company from the family's former accountant.

The family had "no money" and "no one thought we'd win this case".

"This was the only way we could have a lawyer commit to our case," Mr Calvo said.

"Leigh organised dozens of witnesses, she helped manage all the affidavits and all the evidence, she set up community support, and on and on it went. Hundreds of hours."

He said Ms Johnson would appear in early directions hearings in the case without a barrister "and nail it. The average lawyer wouldn't do that."

The couple, represented by Ms Johnson among others, won the case against their former accountant in July 2009.

Justice Bergin was critical of the circumstances in which Ms Johnson had the transfer of shares signed at St Vincent's Hospital in December that year, after Dr Peter Calvo suffered a stroke.

But Daniel Paul Calvo said the arrangement was longstanding and a separate $55,000 payment had been made to Ms Johnson at his insistence during the case to compensate her for her work.

The battle between Mrs Calvo and Ms Johnson rages on, with Mrs Calvo asking the NSW Court of Appeal last week to restrain Ms Johnson from recovering more than $2 million in fees for her legal work.

The court has reserved its decision.