First Class Constable Gavin Storay told Supreme Court jurors on Thursday that while driving to a call-out on May 28, 2013 about 1.20pm, he saw a silver Rav 4 flash its headlights and pull up on the wrong side of Lilydale Road in front of an ambulance.

Constable Storay said he parked nearby and the Rav 4 driver got out and he saw it was Caine Richardson.

He said the Rav 4 passenger was Damien Marshall.

"Mr Marshall had what appeared to be a gunshot wound to his right leg and he said he had been shot," Constable Storay said.

He said he helped paramedics get Mr Marshall out of the Rav 4 and into the ambulance, and he accompanied Mr Marshall in the ambulance to the Launceston General Hospital for safety reasons.

"I asked him who had shot him and he said he did not see and he just said it was a bloke," Constable Storay said.

The Launceston trial of Sean Gregory Richardson, 25, and Damien Wesley Marshall, 31, started on Tuesday.

Mr Richardson and Mr Marshall have pleaded not guilty to two counts of aggravated assault against Robert Williams and Paul Axton, and not guilty to wounding stranger Isaak Heathcote, then 19, on July 29, 2013, about 10.15pm.

The Crown argues the pair committed a drive-by shooting in central Launceston, their intended targets being Mr Williams and Mr Axton, as revenge for the earlier Lilydale Road shooting of Mr Marshall.

Defence counsel for both co-accused have denied their clients had any involvement in the allegations.