Woman heard friend's smash over phone

"The cops are coming, I'll call you back."

These eight words, spoken over a mobile phone, are the last Jake Innes ever said to his long-time friend Ebony McPherson.

Moments later, Mr Innes, 21, lay fatally injured in the wreckage of his friend's maroon Toyota Seca, a coronial inquest heard on Wednesday.

The inquest is examining the circumstances of the crash on June 30 2013, which happened on the Hume Highway near Campbelltown on Sydney's southwest fringe.

At issue is the role played by a pursuing police car and precisely who was at the wheel of the Toyota.

The car's owner and the other occupant, Luke Barrett, who sustained serious head injuries and was apparently flung from the wreck, remembers nothing about the night.

But he told the inquest Mr Innes was probably driving given his own licence had been suspended.

Neither man was wearing a seatbelt, the inquest heard.

Ms McPherson told the court she had no idea at the time that what she heard was an accident.

After Mr Innes referred to police, Ms McPherson said she heard silence followed by crackling and breathing, but thought nothing of it.

A witness recalled driving north on the highway in wet conditions when the car sped past in the outside lane.

He then saw a brief flash of red and blue lights from a marked police car on the road ahead, but heard no siren.

Seconds later, he said, the Toyota veered left across four lanes towards the off-ramp, where it collided with the guard rail.

Police officers told the inquest they flicked the flashing lights on when they saw the car travelling past them at an estimated 150km/h.

They said it then accelerated away before leaving the road.

They found Mr Innes strewn across the front seats, struggling to breathe.

He later died in Liverpool Hospital.

The inquest continues.