WASHINGTON — When Alan M. Dershowitz told President Trump this week that he would join the legal team for his impeachment trial in the Senate, his transformation from a onetime liberal standard-bearer into a conservative provocateur appeared to be complete.
Mr. Dershowitz, 81, a professor emeritus at Harvard Law School, prides himself on being a civil libertarian and a contrarian who isn’t afraid to defend the seemingly indefensible, especially if that person has a high-profile, tabloid-friendly name. His past clients include Claus von Bülow, O.J. Simpson, Mike Tyson and Jeffrey Epstein, the wealthy financier who was accused of sex trafficking and killed himself last year in a Manhattan jail.
Earlier in his career, Mr. Dershowitz was also known as an advocate for the First Amendment who defended neo-Nazi speech and pornography and served on the board of the American Civil Liberties Union. Back then, according to The New Yorker, he also worked pro bono to represent clients involved in challenges to censorship and the death penalty.
Mr. Dershowitz’s connections to Mr. Epstein, however, have proved the most complicating in recent years. In 2014, one of Mr. Epstein’s victims, Virginia Giuffre, said in a court filing that Mr. Dershowitz was one of the Epstein friends to whom she was offered for sex.
Mr. Dershowitz has vociferously denied the allegations. On Fox News, he noted that he had a “perfect, perfect sex life during the relevant period of time.” The accusations even inspired him to write a book, “Guilt by Accusation: The Challenge of Proving Innocence in the Age of #MeToo.”
Since Mr. Trump took office, Mr. Dershowitz has frequently visited the West Wing, consulting with the president and his top aides on various issues, including the Middle East and the Mueller inquiry.
Mr. Dershowitz, who lives in New York, summers on Martha’s Vineyard, and says his family of Democrats is deeply disturbed by his association with Mr. Trump, has known the president as a casual acquaintance since the 1990s.
But Mr. Trump took a greater interest in him after his regular Fox News appearances, during which Mr. Dershowitz often attacked the legal grounds for the special counsel’s investigation into Russian interference in the 2016 election and defended the president’s right to fire James B. Comey as the F.BI. director.
Despite Mr. Trump’s frequent tweets praising him, Mr. Dershowitz has always maintained to reporters that he had no interest in formally joining Mr. Trump’s legal team. In a brief interview on Friday, Mr. Dershowitz said that had not changed and tried to play down his role.
“I’m presenting an independent argument as an independent academic against impeachment, which is a view I’ve held for a long time,” he said.
Mr. Dershowitz is expected to present oral arguments in the Senate trial next week and he insisted that those arguments would be the extent of his involvement in the trial.
“I felt it was important for the Constitution and for precedent and the future of the impeachment,” he said.
His final conversation about joining the team took place on Wednesday night with Mr. Trump himself. “We discussed it and I agreed,” Mr. Dershowitz said.