Retired architect Michael Stratton said he watched Euan Tennant’s 21-year-old sports car in the rear view mirror as it slid sideways into an oncoming car.
Tennant, 22, from York Place, Edinburgh, is alleged to have caused the death of business studies student Laura Campbell, 22, by driving carelessly on 22 September 2010.
The jury at Perth Sheriff Court were told that student Miss Campbell, 22, died as a result of the impact on the A93 north of Scone, Perthshire.
Mr Stratton - who worked as a racetrack marshall - told the court he was not surprised Tennant had lost control of his Toyota MR2 because of the speed he was driving at.
He said: “From the way it came round the corner it was going too fast in my opinion. He looked as if he was about to spin out to the side.
“I’m not sure what speed he was doing,” Mr Stratton, 76, said, “he just appeared to be going too fast. I thought he was going too fast for the corner.
“As I went round the corner I looked in the mirror and saw the car broadside. The car further behind me hit the car which was broadsiding.
“He was in a slide. I realised there would be an accident because the car would be in his way. He was more or less in the middle of the road going sideways.”
Mr Stratton told the trial that he had not seen anything on the road surface which would have explained Tennant losing control of his car on the bend.
He told the court it was dry at the time of the crash because he was on his way to Perth racecourse. He said he did not see any oil spilled on the road.
Architect William Normand had earlier told the jury that Euan Tennant’s vehicle made a “ferocious impact” as it slid sideways down the wrong side of the road into his own car.Mr Normand said: “I was aware of the blur of something coming round the bend and the next thing I was aware of was a car coming towards me sideways and hitting the front of my car.
“It didn’t just slide across the road. It was in a spin situation. Suddenly it just came slipping on the road down towards the front of my car. My first reaction was to slow up and put the brakes on.
“The only thing I could do was try to put the brakes on full and come to a halt. It just happened so quickly. It just spun and then crashed.
“The impact was quite ferocious. The other car hit the front of my car sideways and then went back onto the other side of the road.”
Tennant denies that on 22 September 2010 he caused the death of Laura Campbell by driving carelessly and at excessive speed in Perth, and on the A93 Perth to Blairgowrie road near Scone.
He denies losing control of the car and colliding with Mr Normand’s vehicle, causing fatal injuries to his girlfriend and injuring Mr Normand and his passenger Paul Hirst.
The trial before a jury and Sheriff Michael Fletcher continues.