A woman says she was out with friends when they plucked a teenager off an inner-city street and took her back to a garage in West Auckland, where she was stripped, had her hair cut off and was sexually violated.

Photo: Supplied

The woman was eventually found unconscious, with critical injuries, on a rural road in the Dome Valley, north of Auckland, in May last year.

Jaclyn Keates gave evidence today in the High Court in Auckland, where Nicola Jones is accused of master-minding the kidnapping of the woman she believed had slept with her boyfriend.

Ms Jones and friends Cameron Hakeke, Michelle Blom and Julie-Anne Torrance are charged with kidnapping, assaults using a taser and scissors, and robbery, over the incident in May.

The three women and another man, Wayne Blackett, also face charges of sexual violation.

Keates, who is serving a prison sentence after admitting her part in the attack, said Ms Blom was a neighbour and their kids played together.

She said, in May last year, she went to a birthday party at Ms Blom's place in Kelston, where all the women got their nails done before some of them smoked methamphetamine and they headed into town.

The plan was to go clubbing, but on the way there was talk about enacting revenge on a woman who had slept with Ms Jones' boyfriend.

"I can't remember the exact words, just talking bad about her, that they just wanted to get her and stuff, and that if they ever saw her around, they would get her."

They pulled up on a street behind Auckland's Karangahape Rd, where Ms Jones got out of the car.

Keates told Crown prosecutor Brian Dickey that Ms Jones was only gone a short time.

"Jones had our victim and put her in the car next to her. With her arm around her. With force, sort of quite pushy with force."

She said the victim, who cannot be identified, was put in the back of the car and was repeatedly punched by everyone except Ms Blom, who was driving.

"I didn't actually see her getting hit, but you could tell she was being hurt and then I leaned over and hit her a few times ... and yeah..."

Mr Dickey asked her why.

"Umm, I think it was just, like, in the moment - the peer pressure joining in, as well as being under the influence, so not even having my right-of-mind, which I don't think any of us did that night."

They drove back to the house in Kelston, where the victim spent some time in the boot of the car before being taken down to a garage area below the house.

Keates said she went downstairs to find Ms Torrance had the victim down there, stripped naked and with her hair cut off.

She was asked how the victim appeared.

"Just sad and broken... Just helpless, that there was all of us against her."

Keates said Ms Torrance told her to sexually violate the woman with a plastic tube, but she declined to do so. She told the court she had been disgusted with what had happened and went to her mother's house, which was nearby, to shower.

Once there she received a text message from Ms Blom, saying the dog needed baby-sitting. Keates replied: "That ain't no dog, that's a gutter-rat."

She said she reflected on what had happened while sitting in her mother's home.

"I sat there and read the Bible, no, I just wanted to try and forget everything that had happened."

But under cross examination from Ms Jones' lawyer Maria Pecotic, Keates was asked why her DNA was found on a cricket wicket - a weapon that Keates admitted assaulting the victim with.

"Well, yeah, I don't know how it is but maybe I touched it down there, I don't know."

She denied using one of the wickets as a weapon or minimising her role.

The Crown case was that the woman was taken to a road in the Dome Valley where she was throttled before being bashed in the head with a hammer seven times and left for dead.

The cross examination of Keates will continue on Monday morning.