Former finance professor and Macquarie Bank executive Dr Tony Castagna is behind bars after a Supreme Court jury found him guilty of tax evasion, money laundering and dealing with the proceeds of crime.

Castagna, 70, is facing a maximum jail term of 25 years after the jury found that over a nine-year period up until 2008 he deliberately and dishonestly concealed from the Australian Tax Office millions of dollars in fees and bonuses he received while working as a consultant to Macquarie Bank.

Also found guilty was Castagna’s cousin Robert Agius, a former accountant in the tax haven of Vanuatu, who conspired with Castagna to conceal the money.

Agius, who grew up in the same household as Castagna, is already serving a non-parole period of six years and eight months’ jail, after being found guilty in 2012 for operating unrelated tax avoidance schemes via his Vanuatu-based accountancy firm.

The jury heard that on May 21, 2008, the AFP executed search warrants at Castagna’s home in Gordon, on Sydney’s north shore, as well as at his Macquarie Bank office.

This followed raids by the AFP, in conjunction with Vanuatu police, on the Port Vila home and office of then Vanuatu-based accountant Agius.

The AFP had been intercepting Agius’s phone prior to his arrest in April 2008. Intercepted calls played to the jury revealed the pair’s reluctance to discuss their financial dealings over the phone. In one call Castagna was heard suggesting Agius use “Liz’s cell phone.”

Agius and Castagna were also found guilty of money laundering in that they conspired to deal with property knowing that it was the proceeds of crime. The Crown case was that $4.5 million of Castagna’s money hidden offshore was channeled back to Australia so that he could buy investment properties in the Newcastle area.

To avoid tax, the jury heard the money was returned to Castagna by way of “sham” loans from Agius.

Apart from facing the possible confiscation of his property under proceeds of crime legislation, the ATO is also pursuing Castanga for unpaid taxes and penalties in excess of $10 million.

Castagna is understood to have shares worth $26 million, held via offshore entity Blackall Ltd, in cyber security company Nuix, which is majority-owned by Macquarie Bank.

Castagna is currently a director of Nuix, which helps protect the cyber secrets of and detect financial crimes for their clients which include the Serious Fraud Office in Britain, US Department of Homeland Security, the Australian Defence Force and ASIC.

Two of Nuix’s major clients are the Australian Federal Police and the ATO. It was through the efforts of these two government agencies’ tax-avoidance probe Project Wickenby that Castagna now faces a maximum of ten years for defrauding the ATO and 25 years for money laundering.

Justice Christine Adamson refused bail for Castagna ahead of his sentencing hearing on 25 May.