UPDATED: January 7, 2015, at 9:29 p.m.

On the heels of national attention surrounding allegations that he had sexual relations with an allegedly trafficked minor, Alan M. Dershowitz, a professor emeritus at Harvard Law School, took legal action Monday to intervene in the civil case in which the accusations surfaced as part of an effort to refute them.

The lawyers whom Dershowitz claims fabricated the accusations against him, Bradley J. Edwards and Paul G. Cassell, responded Tuesday by suing him for defamation. Their complaint accuses Dershowitz of “initiat[ing] a massive public media assault on [their] reputation and character.”

{shortcode-7fc26682c828c9d1876a33ceefc3d4c48087109c}

Dershowitz’s court filing Monday came in response to allegations communicated in a Dec. 30 filing in federal court in Florida alleging that a woman, identified as “Jane Doe No. 3,” had sexual relations with Dershowitz in several locations when she was underage at the behest of Jeffrey E. Epstein, a billionaire who previously went to prison after pleading guilty in state court to soliciting prostitution. A philanthropist, Epstein has donated millions of dollars to Harvard.

The allegations against Dershowitz were filed as part of a civil case challenging Epstein’s original plea deal, which Dershowitz helped to negotiate. The filing alleges that Dershowitz negotiated that plea deal, which protected Epstein and any “co-conspirators” from prosecution in federal court, to provide “protection for himself against criminal prosecution in Florida.”

Dershowitz’s Monday motion to intervene in the civil case calls the allegations against him “categorically false” and requests an intervention so that Dershowitz can protect his reputation. Dershowitz also made a declaration, under penalty of perjury, in which he wrote that he “did not ever, under any circumstances, have any sexual contact of any kind with Jane Doe No. 3,” whom he calls a “serial liar.”

The Monday filing challenges the credibility of last week’s accusations against Dershowitz on several grounds, arguing that they are not only fabricated, but also “wholly irrelevant” to the civil case under which they were filed. Dershowitz, in his declaration, alleges that the alleged victim's lawyers “inserted this false and defamatory charge” and “placed it in a legal proceeding, in a public filing, in bad faith in an effort to have the media report it.”

For his part, Dershowitz has denounced the allegations in interviews with several media outlets, including The New York Times, The Wall Street Journal, and The Crimson, among others, and appeared on the BBC and CNN.

Those media appearances were the target of a lawsuit filed Tuesday by the alleged victim's lawyers, Edwards and Cassell, claiming that Dershowitz made statements that were “false and known by him to be false at the time they were made.” The lawyers’ complaint, filed in federal court in Florida, cites Dershowitz’s interview with CNN as well as statements he made to other national and international media sources with the claim that they are defamatory because they attack the “fitness of the Plaintiffs to engage in the honored profession of the practice of law.”

In an interview Tuesday, Dershowitz said he “welcome[s]” the lawsuit against him as an opportunity to combat what he claims are false accusations.

“This gives me a weapon that I didn’t previously have, and the weapon is the power of deposition,” Dershowitz said. “I can now subpoena them, put them under oath, subject them to cross-examination, and prosecute them for perjury if they lie.”

“This is a very positive development for me,” he said.

Edwards and Cassell declined to comment beyond their own court filing.

—Staff writer Andrew M. Duehren can be reached at aduehren@college.harvard.edu. Follow him on Twitter @aduehren14.