Harvard Law professor emeritus Alan Dershowitz said Saturday that there was "no reason" for former Trump adviser Roger Stone's dramatic arrest by the FBI.

Stone, 66, was taken into custody Friday following an early morning raid of his home by special agents in Fort Lauderdale, Florida.

He was indicted by a federal grand jury a day earlier on charges of obstruction, making false statements and witness tampering as part of special counsel Robert Mueller's wide-ranging Russia collusion probe.

Dershowitz said on Fox & Friends that the nature by which Stone was arrested was meant to put pressure on him.

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"They should have simply sent his lawyer a notice saying please show up in the federal court," he said. "It was just a show. ... They're interested in getting information from him about the real target, and that's Donald Trump."

Dershowitz also said that Mueller has come up "relatively empty" regarding crimes that occurred before he was appointed as special counsel.

"[Mueller] will not have -- at least on the basis of what we now know -- hard evidence of any illegal conspiracy between the Trump campaign, certainly not involving President Trump himself and the Russians," he said. "But there will be a circumstantial case that he will build."

He added that it'd be fair to allow the president's team to come up with its own rebuttal report before the release of Mueller's.

"Mueller is conducting a one-sided prosecutorial investigation. He isn't looking for exculpatory evidence, he isn't looking for evidence of innocence. He's looking only for evidence of guilt."

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