A man inserted a beer bottle into a woman's vagina without permission or consent while she performed a buck's night sex show, the Northern Territory Supreme Court has heard.

Key points: Performer at buck's night shocked and upset by alleged assault, court told

Performer at buck's night shocked and upset by alleged assault, court told Kevin Willcocks told police he removed the bottle and apologised

Kevin Willcocks told police he removed the bottle and apologised Defence lawyer says focus will be "mental element" of consent

Kevin Willcocks has pleaded not guilty to one count of sexual intercourse without consent.

The alleged incident happened in front of a crowd of men gathered at a buck's party in the rural area on the edge of Darwin in 2017.

Prosecutors told the court on Monday the alleged victim had worked as a topless waitress and performer for more than a decade, but had never had anything like the alleged offence happen to her in that time.

"She describes going into shock after what happened," lawyer Tiarni McNamee said.

"Her initial action was to kick out at him but [the kick] didn't connect, and then the accused took the beer bottle out of her vagina and walked off."

Ms McNamee told the jury the woman was performing an act involving the projection of dildoes from her vagina when Mr Willcocks caught one and walked up to return it.

But he then inserted his beer bottle into her vagina "without her consent or permission".

"Fortunately for her she didn't sustain any injuries as a result of this conduct," Ms McNamee said.

Ms McNamee said the woman began crying after the incident and called a friend to pick her up, and then phoned the police.

The court heard that when police spoke to Mr Willcocks two days later he told them the night had "gotten out of hand".

Ms McNamee said Mr Willcocks told officers: "my beer ended up in her vagina, I took it out and said sorry to her."

She told the jury that Mr Willcocks said "no" when he was asked whether he had had permission to do what he did.

'Mental element' of charge must be proved: defence

The defence lawyer told the jury to expect a focus on the "mental element" of the charge — that is, whether Willcocks knew about or was reckless to a lack of consent on the part of the alleged victim.

The lawyer said there would be no effort to "drag the complainant through the mud", but the context of the incident was relevant to that consideration.

"This is a buck's party, in the rural area, with enormous amounts of alcohol, and a woman who is in the business of firing dildoes out of her vagina," he said.

Justice Dean Mildren told the jury the matter was a retrial, but that they would not be told why it had not been resolved previously.

"It was not the fault of the accused and you should not draw any adverse inference against the accused merely because this is a retrial," he said.

The trial is expected to run for two weeks.