The woman, who was not a Stanford student, was 22, working full time and living with her parents in Palo Alto at the time of the assault, according to court documents. She described the decision to go to a fraternity party on campus as a last-minute lark and a way to spend more time with her younger sister, who accompanied her.

After she had a meal at home and four shots of whiskey, she told the police, her mother drove her, her sister and two other friends to the Stanford campus at 11 p.m. The women ended up at a party hosted by a fraternity, Kappa Alpha, which was also attended by Mr. Turner.

The woman’s sister told the police that they met several men at the party, but that “one of the guys was very aggressive and trying to kiss everyone,” according to a police report. She later identified that man as Mr. Turner and said she had twice repelled kissing and advances by him.

The sister left the party to accompany an intoxicated friend back to her room, and soon after the victim and Mr. Turner left the party, according to court documents.

Mr. Turner told the police that he and the victim kissed and then walked away from the fraternity house holding hands and ended up on the ground kissing. He removed the victim’s underwear and penetrated her with his fingers. He said he never took his own pants off.

The Swedish students who came upon Mr. Turner and the woman said they stopped to intervene because they saw Mr. Turner on top of her, thrusting his pelvis toward her, court papers and the police reports say. They said she appeared motionless, her eyes closed and her head tilted to the side.