A driver who was speeding at more than 40km/h over the limit with bald tyres on a wet road before a crash that killed an elderly woman has been found guilty of dangerous driving causing death.

Mary Rigby, 85, was driving on Grand Promenade in Bedford when James Murray’s BMW M3 crossed to the wrong side of the carriageway and slammed into her Holden Astra in July 2017.

Murray faced an eight-day trial in the District Court where he argued it was a vehicle defect that caused his car to “steer itself” and lose control.

But it took a jury less than two hours to convict him of the charge.

Mr Murray was also found guilty of dangerous driving occasioning grievous bodily harm to his teenage son, who was a passenger in the car.

During the trial, prosecutors said an analysis of CCTV revealed Mr Murray, 48, was travelling up to 103km/h in a 60km/h zone moments before the fatal collision.

Camera Icon Bedford crash. Credit: 7NEWS

The court was told Murray was trying to perform an overtaking manoeuvre in a narrow gap in traffic when he lost control and mounted a median strip.

The BMW “launched” into the air before crashing into the victim’s car.

The State argued the only pre-existing defect to the car was its balding rear tyres.

But Mr Murray’s lawyer Stephen Walker told the jury a failure involving the car’s differential caused the vehicle to suddenly yaw. The dynamic stability control system was also faulty, he claimed.

Camera Icon Mary Rigby's children Danny Rigby, Anne Hatton, Sean Rigby. Credit: Simon Santi / The West Australian

Murray was granted bail after the verdict, with the court told he helped care for his son, who was still recovering from the crash.

However, Judge Gillian Braddock banned Murray, a fly-in, fly-out worker, from driving in the Perth metropolitan area but allowed him to continue driving in the Pilbara, where he works.

He is facing a minimum two-year driving ban when he is sentenced.

Mr Walker said he would argue for a suspended sentence, but prosecutor James Nicholls said “jail was the only appropriate disposition”.

Outside court, Mrs Rigby’s children Danny and Sean Rigby and Anne Hatton thanked the first responders, emergency services and hospital personnel for trying to save their mother’s life. The siblings also thanked Mr Nicholls.

“We’d also like to thank the jury for making what we believe is the right decision today,” Danny Rigby said.

Murray will be sentenced on November 5.