Advocate depute Iain McSporran told the court last month that Mr Fleeman had initially gestured at Lyons because of his erratic driving.
He said: "It appears that the accused's response to this gesture is what led to Mr Fleeman's death."
The court heard that Lyons said to one of his passengers: "I'm going to sideswipe him."
Previous convictions also included road traffic offences including dangerous driving and careless driving.