Mr Mehajer's lawyer Brett Galloway told magistrate Vivien Swain on Monday his client had been involved in a "relatively serious" crash on the way to the Downing Centre Local Court.

Mr Galloway said he had seen footage of Mr Mehajer on a stretcher being loaded into an ambulance bound for hospital.

It is understood two cars including Mr Mehajer's white Mercedes were involved in the crash in Delhi Street, Lidcombe, shortly before 9am on Monday.

The property developer and former Auburn deputy mayor was due to face trial on Monday for allegedly assaulting a taxi driver outside The Star casino in the early hours of April 2 by throwing an eftpos machine at his face.

He was also charged with stealing a $1500 black iPhone from the driver and "intentionally destroying" a second iPhone belonging to a casino worker.

The court heard there was CCTV footage of the alleged altercation.

Mr Mehajer, 31, was charged with a second assault later that day as he was being whisked away from Sydney City police station on Day Street in a Porsche.

Channel Seven journalist Laura Banks was caught between the car door and the Porsche as Mr Mehajer attempted to flee a media scrum outside the police station.

He was charged with assaulting Ms Banks and was expected to face court on that charge on Wednesday.

Mr Mehajer has been at the centre of a string of legal battles since his lavish but ill-fated wedding in August 2015.

Last week he was ordered to pay more than $1 million, including legal costs, after the District Court found he had not paid for extensive stonework on his "marble palace" in Lidcombe. He did not appear in court.

The assault trial, slated to run for two days from Monday, was adjourned until at least Tuesday after police confirmed Mr Mehajer was at Westmead Hospital.

The court heard he had been given morphine for neck pain.

Mr Mehajer has pleaded not guilty to all charges.