The arrest of Jeffrey Epstein is escalating a long-simmering fight between two of the nation’s best-known lawyers, Alan Dershowitz and David Boies.

The men were friendly, if not exactly friends, until 2015. That’s when Mr. Dershowitz learned Mr. Boies was representing Virginia Giuffre, a former Florida resident who had alleged Mr. Epstein sexually abused her as a minor and prostituted her to his friends, including Mr. Dershowitz. Mr. Epstein has pleaded not guilty to charges of sex-trafficking of minors and conspiracy.

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