An unlicensed driver accused of killing his son in an accident while drink-driving was more than five times over the limit, a court has heard.

Anthony Paton, 56, has pleaded not guilty in the ACT Supreme Court to charges of culpable driving causing death and culpable driving causing grievous bodily harm.

Andrew John Paton, 29, of Ngunnawal, died after the car his father was driving along Gundaroo Drive veered into the opposite lane and collided with an oncoming car in July 2009.

The defendant and the passenger of the other vehicle were also seriously injured in the accident.

Jurors on Monday heard there was no contest the accused had an expired driver's licence, returned an alcohol reading of 0.281, and the car was unregistered.

Crown prosecutor Shane Drumgold, in his opening statement, said Paton's intoxication and driving manner had led to the accident.

But Paton's defence barrister, James Jeffrey, said his client denied causing the fatal accident.

Mr Jeffrey said the accident had been caused by a passenger activating the car's handbrake moments before the collision.

A rear passenger in the vehicle told the court, from the witness box, he had been drinking with the defendant, deceased and another man on the day of the accident.

He said Paton had begun driving erratically - speeding and trying to slide the car around corners - after fleeing a minor crash at the Florey shops.

The witness said Paton had attempted a similar manoeuvre when he lost control of the vehicle and collided with an oncoming car.

The man admitted his distressed voice mentioning a handbrake could be heard in the background of a triple-0 call, made by passersby who stopped to help, which was played in court. But he said he did not know why he had mentioned the handbrake as he and the other passenger did not engage it.

An ACTION bus driver who witnessed the fatal smash said the car had drifted onto the verge before fishtailing and spinning into oncoming traffic. The court heard footage of the accident, captured on the bus CCTV cameras, would be played for jurors on Tuesday morning.

The trial before Justice Hilary Penfold continues on Tuesday.