On the eve of Michael Flynn’s sentencing for lying to the FBI, retired Harvard law professor Alan Dershowitz joined the chorus of hyperventilating President Donald Trump supporters who claim that Flynn may have lied to the feds, but that doesn’t mean he broke the law.

“Flynn did not commit a crime by lying,” Dershowitz said during a Fox News interview Monday. “The lie has to be material to the investigation. And if the FBI already knew the answer to the question and only asked him the question in order to give him an opportunity to lie, his answer, even if false, was not material to the investigation.”

“Lying to the FBI is not a crime,” Dershowitz added.

It should be noted that lying to the FBI is indeed a crime when the falsehood in question is material to an investigation, and prosecutors have determined that Flynn’s statements were.

Nonetheless, Dershowitz’s assertion has become a favorite for critics of special counsel Robert Mueller’s investigation of Russian meddling in the 2016 election. Those critics believe the FBI tricked Flynn, a former Trump aide, into lying.

ASSOCIATED PRESS Michael Flynn﻿ will be sentenced Tuesday.

The idea came directly from Flynn’s legal team. In a memo last week, Flynn’s lawyers said he was not explicitly told there would be penalties for lying. (However, a recent Washington Post fact check on the matter chalked the filing up to some strategic spin. In reality, it noted, legal experts haven’t found Flynn’s treatment to have been unusual or unfair.)

Among those preaching the story are right-wingers like Trump attorney Rudy Giuliani and Fox News’ Judge Jeanine Pirro, who’ve taken part in a sort of myth-making. But Mueller isn’t buying the defense.

In his interview, Dershowitz doubled down on the narrative that Flynn isn’t in the wrong, contending the former aide did not make “a material misstatement” in the investigation and predicting that his guilty plea could be nixed.

“I think the judge has the authority to throw out the plea if he believes that the plea was not to a crime, and I think he should find, as a matter of law, that when you tell an untruth to the FBI about a matter that they already know the truth about, they already know the answer, when the only purpose of the question is to get you to lie, that that’s not a crime.”

Dershowitz has cemented himself as a staunch defender of the president and released a book last summer titled The Case Against Impeaching Trump.

On Twitter, former federal prosecutor Renato Mariotti dismissed Dershowitz’s argument as deliberately deceptive.

Dershowitz often misleads the public through sleight of hand like this. His deceptive phrases are so carefully worded that I'm convinced he is deliberately deceiving people. — Renato Mariotti (@renato_mariotti) December 17, 2018