The lawsuit was filed Tuesday in Cook County Circuit Court. It concerns a party at the fraternity house in the 5000 block of South University Avenue on Feb. 7, 2026, according to the complaint.

Doe alleges that a fraternity member gave her a shot of unidentified alcohol and urged her to drink it. She says she soon felt unsteady and lightheaded, and that the man led her to a bedroom and sexually assaulted her despite her saying she felt impaired. The complaint alleges she was unable to consent or physically or verbally refuse. It also says she asked him to use a condom and he refused.

The lawsuit further alleges that another fraternity member prevented Doe’s friends from going upstairs to check on her until the alleged assailant gave permission. Her friends eventually found her, still unconscious, and helped her leave the house, according to the complaint.

Doe reported the assault to Chicago police the next morning after finding bloodstains in her underwear, the lawsuit says. Police confirmed receiving a report and said the investigation is ongoing. Police also said Doe went to Illinois Masonic Hospital for treatment.

The complaint says University of Chicago Police contacted Doe in the days after the incident and made an incident report, but have not provided her with records related to the case without a subpoena.

The lawsuit points to earlier reports tied to the fraternity, alleging police investigated multiple reports of sexual assault involving the chapter beginning in 2009. It cites two reports made five days apart that January, an incident connected to the fraternity’s weekly “Bar Night” gathering in which a person was taken by ambulance to an emergency room, and an anonymous 2022 social media post describing an assault at the house.

The complaint alleges that reports of sexual misconduct continued between 2009 and 2026, including reports made through the fraternity’s internal processes. It says the national organization did not discipline the University of Chicago chapters, restrict or condition their social events, require secured living areas during parties, or mandate sober monitors on residential floors.

The chapter was not listed as being on probation or under disciplinary status at the time of the report. The university and Alpha Delta Phi had been asked for comment, but no response was reported. The lawsuit’s claims are allegations, and no findings of liability are described.

Chicago police are separately investigating an October report of sexual assault at the University of Chicago’s Alpha Epsilon Phi house. Police said that investigation is ongoing and a person of interest has been identified; the two cases are not connected.