Mr Merrigan worked as an installer for Macrack.
The statement from Joanne Glasson of Macrack said that in February 2010 someone complained that Mr Merrigan harassed a woman on the side of the road on a freeway.
The company paid for a defensive driving course for its installers, but more complaints about Mr Merrigan followed - one in March 2011 and another in June 2012.
He was given a formal warning after the 2011 complaint, and a note on his file said he had been counselled and asked to modify his driving.
Heke reportedly told police that Mr Merrigan tailgated him on the Gateway, made rude gestures and pulled off the road ahead of him in the lead-up to the fight.
The court heard the many witnesses gave conflicting and, at times, graphic accounts.
Justice Roslyn Atkinson said the case for manslaughter was stronger than for murder.
In granting bail, she said there was no suggestion Heke would pose a risk to anyone if strict bail conditions - including a ban on driving - were imposed.
Almost a dozen people turned up to the hearing in support of Heke, including his fiancee, who had been due to marry him this month.
"He's a lovely guy in a bad situation," Heke's lawyer Adam Magill told reporters.
"It will come out in the wash, what's happened."
The case is due to return to court on January 25.
- AAP