Donald Trump has vowed to testify on Monday in writer E. Jean Carroll's defamation case in New York, but one MSNBC legal analyst thinks it is a fake-out.

Attorney Lisa Rubin posted a prediction on Saturday, and used her knowledge of the legal system to bring it home.

"Any former trial lawyer can tell you that witness prep is essential. And with a plaintiff, defendant, or C-suite exec of either, that prep begins well in advance of trial & often involves faux cross. And that brings me to everyone’s fave defamation defendant, Donald Trump," Rubin wrote, adding that the former president "has a jam-packed calendar of campaign events in NH yesterday, today, and tomorrow."

"That begs the question: When is he fitting in that witness prep? And are any of his lawyers in the Carroll case even in NH with him?" she asked.

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Rubin goes on to say the ex-president "has faked us out on testifying at least twice." "In last spring’s Carroll trial, he repeatedly threatened he would testify, but he never even entered the courtroom," she elaborated.

"Then, during the fall’s trial of the NY Attorney General’s civil fraud case, he had no choice but to testify when called in the AG’s case. But he declined to testify in his own defense at the last minute."

Now, she says, we are in a familiar spot.

"And so here we are again, awaiting Trump’s promised testimony in yet another civil trial. But he’s backed out before, and there is no indication he’s taking any time this weekend to prepare himself," the lawyer wrote. "If on late Sunday night, say, we learn he’s staying put in NH, I will hardly be shocked."