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The investigation into Hillary Clinton's private email server is entering a "very, very dangerous phase" for the Democratic presidential front-runner, Judge Andrew Napolitano said on "Varney & Co" today.

As federal prosecutors prepare to interview several of Clinton's closest aides, it's a sign that they're finished gathering and corroborating evidence, Judge Napolitano explained.

He said that most criminal defense attorneys will not let their clients be interviewed by the FBI and federal prosecutors, because the government is not obligated to reveal what evidence they have.

Whether the aides agree to be interviewed or not, the final phase of the investigation will be when Clinton herself is offered the chance to come in and speak to prosecutors, Judge Napolitano said.

He added that he expects the interviews with the aides to take place - or not take place - in the next two weeks. The interview with Clinton - if it does happen - should be in the next month.

"This is a day of reckoning that she devoutly wishes does not come," the judge said. "She has said she can't wait to get in and talk to the FBI."

"Nobody believes that! No one, when they're being investigated by the FBI, can't wait to get in there! It's the last people in the world you want to see!"

Watch the segment above.

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