Wall Street Journal video reporter Shelby Holliday says Special Counsel Robert Mueller sent a "signal" to President Trump with Michael Cohen's guilty plea.

Cohen, Trump's former attorney, on Thursday pleaded guilty to lying to Congress about a Trump real estate project in Russia.

It marked the first time Mueller’s team charged Cohen as part of its investigation into Russian meddling and potential collusion with Trump campaign associates during the 2016 presidential election.

The president swiftly fired back after news of the new guilty plea broke, blasting Cohen as a "weak person," and claiming his former attorney was "lying" to get a reduced sentence.

On "America's Newsroom" Friday, Holliday said this is a sign that Mueller believes Cohen and will continue to use him as a witness in his probe.

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"If you talk to a lot of legal experts, they say what has changed is that Mueller is sending a signal to Trump that he knows something about this deal and possibly other things Michael Cohen has told Mueller that we are not privy to," she said.

She noted that the aborted Russia real estate deal was included in written questions to Trump by Mueller's team. Last week, Trump's legal team submitted the answers.

"That's a signal to Trump that Mueller understands some of the lies that have been told to Congress and, possibly, some of the lies that President Trump wrote down in those answers," Holliday said.

Ed Henry said he has spoken with Trump's personal attorney, former New York City Mayor Rudy Giuliani, who insists that there is no conflict in Trump's written answers.

"What we don't know is what Bob Mueller thinks about those answers," Henry said.

Watch the "America's Newsroom" discussion above. 

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