Dershowitz, 81, has been a well-known figure in U.S. legal circles for decades.
The Harvard Law School professor successfully defended former National Football League star O.J.
Simpson on charges of murdering his wife and a friend of hers in 1995 and represented financier Jeffrey Epstein against sex crime charges, for which he pleaded guilty in 2008.
Dershowitz says he voted for Trump's Democratic presidential rival Hillary Clinton in 2016, but has since emerged as a high-profile defender of Trump on cable television and has written a book opposing his impeachment.
At the Senate trial, Dershowitz presdented constitutional arguments against impeachment and removal from office, according to Trump's legal team.