Convicted criminal James March, 27, walked onto a Canberra property at random one night in September last year, entering a granny flat through an open door.

Inside, he found a young woman, whom he repeatedly raped and sexually assaulted for two hours.

March, a large, intimidating man, threatened to come back and make the young woman "disappear" if she told anyone.

Her mother and brother were inside the main house during the attack, but heard nothing.

Crown prosecutor Trent Hickey said the terrifying crime not only breached the sanctity of the victim's home, but had a devastating, long-term impact on her and her family.

"It's not overstating it to say this would be everybody's worst nightmare," he said.

"It simply would have been terrifying for her."

Mr Hickey was speaking at March's continuing sentencing hearing before Chief Justice Helen Murrell in the ACT Supreme Court on Wednesday.

He urged the court to consider the crime as being in the worst category of sexual assaults.

March, he said, showed no remorse, and his size and erratic behaviour must have intimidated and terrified the victim.

The court heard he had only just finished a term of imprisonment months before the rape, and still had a suspended sentence hanging over his head.

March's defence lawyer Louise Taylor said her client has continually been in contact with the criminal justice system.

He had a dysfunctional and unstable background, was taken away from his parents at a young age, and used drugs from early in his life.

March drank heavily, typically going through 1.4 litres of spirits a day.

Ms Taylor said he had difficulty remembering the crime.

She said he accepted now was as good a time as any to turn his life around, and noted he was still a young man.

The gravity and seriousness of the crime, she said, were not lost on him.

Chief Justice Murrell will hand down her sentence on Thursday morning.