The four hosts of Fox News’ Outnumbered spent the first half of their show dismissing ex-Trump lawyer Michael Cohen, who pleaded guilty Thursday to lying to Congress about his role in his former boss’ Moscow dealings, as a proven “liar” who is not to be trusted about anything he says.

And then Judge Andrew Napolitano showed up.

As he has done numerous times before, the senior judicial analyst patiently explained to Fox hosts why the Cohen news is not something to dismiss and could be potentially devastating for President Trump.

If the president is right when he says he “could do whatever he wanted in terms of his business dealings, just like any other business person,” Harris Faulkner asked, then why would Cohen have lied to Congress about what he was up to during his 2016 trip to Moscow?

“Who knows why he would lie?” Napolitano replied. “He told a federal judge this morning the reason why he lied was to stay on political message, whatever that means. I guess he is saying today, at the time he lied, he thought he would help the president by lying. Obviously, that is not the case.”

In other words, the judge explained, the fact that Cohen felt he had to lie on Trump’s behalf is what makes his guilty plea today damaging to the president.

As for Trump’s defense that he never moved forward with the plan to build a Trump Tower in Moscow, Napolitano explained: “The easiest charge for the government to prove is conspiracy, because conspiracy is an agreement to do something wrong even if the ‘something wrong’ never happened.”

“So was Michael Cohen’s trip to Moscow part of an agreement or series of agreements to do something wrong for the campaign?” he continued. “I mean, if that’s the case, then we would have to see or hear whatever Michael Cohen told the prosecutors. But whatever it was, it was enough to get them to ask a judge to lower his jail time exposure considerably.”

Napolitano admitted that Cohen is “not a credible person” owing to the fact that he has “twice pleaded guilty to crimes of deception.” That led co-host Kennedy to ask how, given that fact, Special Counsel Robert Mueller should believe anything Cohen says.

“Great question, when they can corroborate what he told them,” Napolitano replied, explaining that prosecutors would only agree to a plea deal if they have forensic evidence like emails, phone calls, or text messages to back up what a witness like Cohen says.

Asked again by another co-host if “any of that information is usable if Michael Cohen is a liar and not credible,” Napolitano seemed momentarily stunned that he had to answer the same question once again.

Faulkner helped him out by jumping in with: “If you back it up it is.”