The Crown alleges that a 16-year-old girl was raped by a group of men at a party at Woodend Beach.

The Crown alleges a drunken 16-year-old girl was raped by a group men at a Woodend Beach party, but the defence says it was a case of willing sexual activity regretted afterwards.

Some of the North Canterbury men charged told police that the girl was a willing participant in the sand dune sex in May 2014, but one Crown witness would say she was "shocked, shaken, and distressed" when he intervened, the High Court at Christchurch was told.

Five men have gone on trial in the two-week trial before Justice David Gendall and a jury.

Crown prosecutor Deidre Orchard said the jury would have to decide whether the complainant was a "flirting seductress" or whether she had been taken advantage of by being taken off against her will to have sex in the dunes.

Isaac Jason Mould, 21, from Woodend, Brook Sebastian Norris, a 22-year-old landscape gardener from Brooklands, Troy Matua James McIver, 21, a rigger from Rangiora, Ky Robert Reginald Reid, a 21-year-old logging contractor from Woodend, and Stuart Mitchell Lewis, 21, deny three charges of rape and one charge of unlawful sexual connection.

The Crown alleges that the girl was raped by Mould, McIver, and Norris, and Lewis sexually violated her.

All the men present have been jointly charged on the basis that they either committed the crimes or actively helped or encouraged someone else to commit the crime, or that they formed a common intention to sexually assault the girl.

Mrs Orchard said the girl had gone to a bonfire on Woodend Beach on a Friday night in May, 2014. She had a slight build and became quite intoxicated on pre-mixed drinks, before Norris and McIver led her into the dunes. She told them she wanted to go back to the bonfire.

When they began kissing her, none of it was welcome. She was then raped and violated until another young man went to investigate what was happening and heard her scream twice. He saw McIver on the girl and pulled him away. He would say the girl was "in a bad way…shocked, shaken, and very distressed", Mrs Orchard said.

The girl was bruised by being held down but had tried to deal with it the issues herself, Mrs Orchard said. Eventually, her mother heard what had happened and a complaint was made two months after the alleged incident.

For Mould, Tony Greig said his client would say the girl had been happy and had encouraged him to have sex. It may be she had been embarrassed and had later regretted what she had done.

Andrew McCormick, for Lewis, said his client denied doing any sexual activity, or being a party to them. He saw sexual acts being performed but she was not protesting nor showing signs that she didn't want what was happening.

A woman at the gathering would describe the girl openly flirting and kissing at least three of the defendants, and then willingly leaving the bonfire with two of them.

April Kelland said Norris denied raping, or being a party to rape, or any knowledge of the sexual violation. She told the jury: "Alcohol provides a general background to a lot of the evidence. You will need to consider how alcohol affects the reliability of the evidence."

Steve Hembrow, defence counsel for McIver, said his client admitted participating in consensual sexual acts.

"My client says this case is about regretted sex. In the cold light of the following day, or the day after, that is what the complainant felt. It is about a young girl who perhaps is ashamed of what happened that night and is trying to justify it in her mind, and now believes it."

The girl said in an evidential interview that she had gone to the bonfire gathering on the beach, where it "started to get creepy". One of the men had started "saying gross stuff to me" and then she remembered two of them taking her into the dunes.

"Suddenly there were all these guys around me. I remember not much, just . . . yuck . . . disgusting stuff, and screaming, kicking, trying to get away."

She said four boys – who she named – had sex with her when she did not want to, and she had told them "no".

The trial continues.