Alan Dershowitz has filed counterclaims for defamation and intentional infliction of emotional distress against a Jeffrey Epstein accuser who has claimed she was forced to have sex with the former Harvard law professor.

The counterclaim was filed late Thursday in the U.S. District Court for the Southern District of New York in litigation begun by Virginia Giuffre when she sued Dershowitz for defamation in April. Giuffre claimed Dershowitz aimed to damage her credibility with the media by calling her, among other things, a "serial liar" and "prostitute."

Dershowitz—who has repeatedly denied he ever had sexual contact with Giuffre—has long maintained that her suit was an extortion plot, and he made clear in recent weeks that he planned to seek damages.