An Adelaide man who hit and killed a teenage girl with his Lamborghini three years ago has been found not guilty of death by dangerous driving.

Alexander Campbell had already admitted to driving without due care when he lost control of his Lamborghini Huracan at Glengowrie in June 2019.

But he pleaded not guilty to driving dangerously in the crash that killed 15-year-old Sophia Naismith and injured her friend as they walked along the footpath outside of a Chinese restaurant on Morphett Road.

Judge Paul Muscat, who presided over the trial without a jury, said it could not be proven beyond reasonable doubt that Mr Campbell deliberately accelerated in a dangerous manner.

Mr Campbell's lawyer, Craig Caldicott, had told the court his client was travelling at 53 kph at the time he lost control and the prosecution had not proved dangerous driving under the criminal law.

Prosecutor Kos Lesses said there had to have been "excessive throttle ramp" for the car to respond the way it did and that Mr Campbell "put his foot down" moments before the fatal collision.

Mr Campbell did not give evidence in his defence or call any witnesses.

Supercars and stunt driver Luke Youlden gave evidence as an expert witness, saying the car must have been in sports mode before Mr Campbell lost control of the vehicle.

The family of Sophia Naismith erupted in tears when the verdict was read out.

Mr Campbell will be sentenced later for aggravated driving without due care.

More to come.