A rape complainant had DNA from three males on her underwar, a jury in the High Court at New Plymouth has been told.
Two teens, who were 18-year-old New Plymouth High School students at the time, face a total of seven charges involving a then 17-year-old girl.
Forensic specialist Turlough Thomas-Stone said he examined DNA samples taken from the woman's underwear, and swabs from her mouth and genitals.
He said due to the complex nature of the DNA found it was not possible to identify any individual's profile.
Mr Thomas-Stone also could not say whether the traces of DNA were recent or had been there for weeks or months.
Earlier, another expert witness, Diana Kappas, said she could not rule out that the complainant had been under the influence of drugs or alcohol at the time of the alleged assault despite finding no trace of either in her blood specimens.
Ms Kappas the blood samples were taken after more than 20 hours from the alleged offending and it was possible for alcohol and drugs had metabolised by then.
The complainant said she found out she had been in a threesome the following day after being told a video had been had been posted on social media.
Earlier, a teenage witness told the court he entered his bedroom to find one of the defendants having sex with the complainant, while the other sat on the bed wrapped in a blanket.
Under cross-examination, the witness said he was angry with what he saw and would have intervened if he had thought anything bad was happening.
The Crown argues the woman was in no position to consent because she was too drunk, while the defence says any sexual activity was consented to.