A veteran costume designer sued Robert Knepper on Wednesday, alleging that the “Prison Break” actor defamed her when he denied her allegations of sexual assault.

Susan Bertram alleges that Knepper grabbed her by the crotch and pinned her against the wall of his trailer during the filming of “Gas Food Lodging” in 1991. She recounted the alleged assault in an article in the Hollywood Reporter on Nov. 8.

Knepper denied the allegation in an Instagram post, saying he was “shocked and devastated to be falsely accused of violence against a woman.” In a follow-up story in the Hollywood Reporter, four more women accused Knepper of sexual misconduct.

Knepper issued a denial for that story, in which he said, “I need to reiterate that these allegations against me are false. We have lost the presumption of innocence; we have lost ‘due process’; and we have lost the ability to review evidence — allowing the media to become both ‘judge and jury.'”

In the lawsuit, Bertram’s attorney alleges that the denial amounts to defamation.

“The false Knepper statements have interfered with the Plaintiff’s ability to find work, have damaged her reputation in Hollywood and the entertainment community, and have caused her great mortification and emotional distress,” the lawsuit states. “Due to Defendant’s false statements regarding Plaintiff’s accusations, Plaintiff has had to refute the false statements to friends, family, potential employers and co-workers. This has been mortifying and humiliating to Plaintiff.”

Following the reports, Warner Bros. conducted a review and found no evidence of allegations on the set of Knepper’s current show, “iZombie.”

Knepper’s representatives did not immediately respond to a request for comment.

Robert Knepper suit by gmaddaus on Scribd