Judge Andrew Napolitano said Wednesday on "Your World" that if Michael Cohen testified truthfully about a phone call he overheard between President Trump and former associate Roger Stone, it could cause trouble for the president.

Napolitano said that President Trump, however, does not need the "monkey on his back" that is the Cohen hearing, particularly while he is pursuing diplomatic ends with North Korean leader Kim Jong Un at the same time.

But Napolitano said that a key piece of testimony from Cohen centered around an alleged phone call he claimed to overhear between Trump and Stone.

Cohen testified that Stone told Trump he "just got off the phone with [WikiLeaks founder] Julian Assange" in regard to hacked DNC emails from the 2016 election.

As Fox News reported:

[Cohen] waded into the investigation over Russia’s meddling in the 2016 election, accusing Trump of knowing that an adviser, Roger Stone, was reaching out to WikiLeaks about the publication of stolen Democratic National Committee emails during the campaign. Trump has denied advance knowledge. On Wednesday, Stone denied the claim, telling Fox News: “Mr. Cohen's statement is not true." WikiLeaks also released a statement saying, "WikiLeaks publisher Julian Assange has never had a telephone call with Roger Stone."

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"[Cohen] paints a potentially grave picture for the president if the conversation he says he overheard with Roger Stone is true," Napolitano said, adding that it would mean Trump apparently lied under oath in written responses to questions from Special Counsel Robert Mueller.

Napolitano said that one uncertainty about the claims is whether the government can "corroborate" Cohen's testimony.

Watch more above.

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