In a trial that began in the Supreme Court on Monday, the Crown alleges that one night in January 2015, Matthew Shaun McGrail, 25, forced himself on the girl after a night drinking in Civic.

The girl was staying at McGrail's flat with her boyfriend that night.

Prosecutor Jane Campbell said he had been charged with five offences: two counts of sexual intercourse with a young person under 16, two of indecent acts and one of attempted sexual intercourse.

The Crown alleges he knew the girl was 15 at the time.

She said the court would hear evidence from the girl about the night of the alleged offences, and a forensic expert would say DNA collected from swabs on the man's penis and hands showed "extremely strong support" for it being the girl's DNA.

On the night in question, the girl's boyfriend had left the apartment to find a cigarette, during which time McGrail returned from Civic.

It's alleged while they were alone in the apartment, McGrail started tickling the girl's legs and flattering her. He then forced himself on her using his hands and mouth, while she repeatedly told him, "No".

She left the apartment and called her boyfriend and McGrail's girlfriend and told them what had happened. She went to police, and the court would see video of her interview later that morning, Ms Campbell said.

While she was with police, McGrail was taken into police custody after he punched a window at the Braddon unit complex.

He was later that morning arrested over the alleged sexual offences, and consented to swabs being taken from his body and mouth.

Defence barrister Richard Thomas said McGrail denied the allegations.

"It's clearly a case of the complainant's word against my client's word," he said.

"You'll hear the accused shortly after [the incident] deny that anything had happened, so it's not clear cut, it's not straightforward."

He said it would be important for the jury to understand what DNA evidence was, which he said was an opinion "based on assumptions".

The trial continues before Justice John Burns.