Thompson, 30, of Batemans Bay, jumped on the bonnet and roof, and then put a log through the windscreen to cover the damage sustained during a southside hit and run in March 2012.

He then walked back to the scene to see paramedics and police, and "freaked".

His partner, the passenger at the time of the accident, sent the car to the wreckers the next day.

Thompson faced trial in the ACT Magistrates Court on Wednesday having pleaded not guilty to a charge of culpable driving causing grievous bodily harm.

The defendant's lawyer, Soraya Saikal, argued her client's behaviour had not contained the level of gross negligence required to prove a charge of culpable driving.

Thompson pleaded guilty to a charge of driving while disqualified and the prosecution also filed back up charges of negligent driving and not stopping to provide assistance.

The court was told Thompson had been unlicensed when he got behind the wheel to drive his partner from their Wanniassa home to her mother's Kambah house on the morning of March 7.

The pair drove along Wheeler Crescent to a roundabout at the intersection with Fincham Crescent.

About 7.45am, Thompson's car struck cyclist Hugh Trounson as he rode through the junction.

Thompson paused briefly before speeding away from the accident.

Mr Trounson spent a week in hospital with fractured vertebrae and ribs, gravel rash, a cut mouth and a knee injury.

He said he had seen the car slow before the crash and assumed it would give way.

"It was just an explosion, next thing I knew I was just lying on the road on my side," Mr Trounson told the court on Wednesday.

"That accident, it doesn't look like a lot on the physical injury side of things but that accident changed my life.

"I reckon I've aged quite a bit since that accident, I was maintaining a regime of health but after … [my health] will never get back to what it was."

Thompson told the court, from the witness box, he had slowed the vehicle at the roundabout, looked for other road users and started to accelerate when his partner yelled to look out.

He said he turned to look at her but then heard a bang and saw a body hit the windscreen.

"I didn't ever see him until he was on my windscreen," he said.

"Then I got scared and took off. I knew it was my fault. I regret it."

He admitted he had damaged the vehicle in a bid to escape detection.

Prosecutor Jane Campbell said Thompson had been driving under "optimal conditions" and only a "gross lack of care" could have caused the accident.

Ms Campbell said the vehicle's passenger had seen the cyclist and warned the defendant but he responded by taking his eyes off the road and accelerating, rather than braking heavily.

He then fled, which the prosecution argues is part of the gross negligence required to prove culpable driving.

"This was not a case of momentary inattention," she said.

"This was a complete failure to keep a lookout for other road users. He was the driver and he drove away."

Ms Campbell said Thompson's destruction of the car to avoid police detection displayed a consciousness of guilt.

But the defence lawyer said the charge of culpable driving had not been supported by the evidence, which indicated Thompson had shown a level of care before the collision.

Ms Saikal said the victim, Thompson, and the passenger all told the court that the vehicle had slowed as it approached the roundabout.

Thompson had given evidence that he had slowed and kept a look out as he was aware a nearby school meant children would be in the area.

The defence lawyer also argued medical evidence had not proven Mr Trounson had suffered injuries that constituted grievous bodily harm.

Magistrate Robert Cook will hand down his decision next month.