Dylan Leo Victor Lee pleaded guilty in the Launceston Magistrates Court in April to causing grievous bodily harm to his passenger, Ashton James Whittingham, and killing father-of-two Adrian Tudor in the crash.

Appearing in the Launceston Supreme Court on Wednesday, Lee wiped tears from his eyes as he entered guilty pleas to two charges - being a driver involved in a crash and failing to stop and driving while disqualified - also related to the fatal crash.

The court heard Lee had a number of prior convictions for driving while disqualified, with his most recent charge at 10am on the day before the fatal crash.

Lee's bail document for the disqualification was found in the car at the crash scene.

On September 7, the 23-year-old was driving a Ford Falcon sedan dangerously through Launceston when he smashed into Mr Tudor, who was on his way home from a night shift at Coles just before 2am.

Lee was going between 117 km/h to 123 km/h when he drove through a red light, hitting the driver's door of the victim's Hyundai station wagon at the intersection of Wellington and Frederick streets.

Mr Tudor's car moved 51.1 metres as a result of the impact and he had to be cut from his vehicle by emergency services.

Lee called out to his acquaintance to leave but Mr Whittingham was stuck, so Lee helped him out of the car and then fled.

Defence lawyer Lucy Flanagan told the court Lee panicked, left the scene and called his mother.

The court heard Lee's mother was not aware he'd been involved in a crash, but she drove from Blessington to pick him up.

"He wasn't trying to avoid police, he just wanted to speak to his mother first," Ms Flanagan said.

Mr Tudor and Mr Whittingham were taken to hospital by Ambulance Tasmania, but Mr Tudor died a short time later from a massive trauma to the right side of his chest.

The killer was remanded to reappear for sentence on June 20.