A woman who says she was sexually assaulted at a Colorado State University fraternity house has sued Phi Delta Theta, alleging the fraternity was negligent in maintaining a safe environment. The lawsuit concerns an alleged assault on Oct. 5, 2024, at the chapter house in Fort Collins; CSU is not a defendant. The woman, a former CSU student, alleges that after attending a party southwest of campus, she accepted a drink from a man she did not know and quickly experienced tunnel vision. She told police she felt more intoxicated than the amount of alcohol she had consumed would explain, according to police records. The lawsuit alleges the man, later identified as a Phi Delta Theta member, arranged for a fraternity designated driver to pick them up. The woman told police she asked to be taken home but was instead brought to the fraternity house east of campus, where she alleges the assault took place. Police records indicate video showed her being walked into and later out of the house. She reported the incident to friends that night, saying she had trouble remembering what happened and believed she had been sexually assaulted. She went to a hospital the following day, police records say. Fort Collins police collected video and physical evidence, including clothing from both people, and conducted a toxicology test. Police logs say the test detected THC and Zoloft. The records also say the accused man hired an attorney and that the designated driver disputed the woman’s account of being taken to the fraternity house against her will. Police closed the investigation without sending it to the Larimer County District Attorney’s Office for consideration of charges. The DA’s office said police consulted prosecutors about possible investigative steps but never formally presented the case or asked that charges be filed. The office said people with new information can contact Fort Collins police. The lack of criminal charges does not determine whether an assault occurred. Alison Jones-Lockwood, CEO of the Sexual Assault Victim Advocate Center, said most survivors do not report sexual assault to law enforcement. Speaking generally, she said a decision not to pursue charges does not mean an assault did not happen; it means there was not enough evidence to move forward. CSU’s process reached a separate conclusion. The university said that, after an investigation and hearing, the student named in the lawsuit was found responsible for violating its policy prohibiting sexual assault and was suspended for one year. He cannot seek readmission until completing assigned sanctions, including a behavioral-health assessment and any recommended clinical treatment. CSU said its student-conduct process is separate from a criminal investigation and uses a different standard of proof. Because the alleged incident occurred off campus, the criminal investigation was under Fort Collins police jurisdiction. The university said it was not a party to the lawsuit and declined to comment further on the litigation. Phi Delta Theta said it removed the accused member, who then moved out of the chapter house. The fraternity said the university’s Title IX investigation did not lead to disciplinary referrals against the chapter or other members. In a statement, it called sexual assault abhorrent and said anyone who commits it forfeits the privilege of membership. Fort Collins police declined to discuss the specific investigation, saying the department takes sexual-assault reports seriously.