Alan Dershowitz said there's no doubt that FBI agents tried to trap Michael Flynn into making false statements, but there is still no explanation for why the then-National Security Adviser lied to federal agents about a non-crime.

Last week, Flynn's legal team filed court documents alleging that the FBI pushed Flynn not to bring a lawyer to his fateful Jan. 24, 2017 interview with agents at the White House.

In response, Mueller's team was ordered to release key documents related to the case in advance of Flynn's sentencing on Tuesday. Flynn pleaded guilty to lying about his conversations with the Russian ambassador during the presidential transition, but many experts expect him to receive no jail time after he cooperated with Mueller's investigators.

On "America's Newsroom" Monday, Dershowitz said it's not a question of if Flynn lied or if the FBI treated him unfairly, because both are true.

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"He did lie. He had the opportunity not to lie. Nobody can figure out why he would lie. He obviously knew there were transcripts," Dershowitz said. "But ... was he treated unfairly? The answer is, absolutely yes."

He explained that FBI agents "sprung the trap" during the informal White House interview by asking Flynn questions to which they already knew the answers.

"The question for the American public is: Do we want the FBI to be springing morality tests on our citizens?" Dershowitz said. "That's not a proper function of law enforcement."

He argued, however, that Flynn did not commit a crime by lying to the agents, because the lie was not "material" to the investigation.

"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," Dershowitz said.

Dershowitz noted that Flynn, as a member of Trump's transition team, had the authority to speak with the Russian ambassador in December 2016, and if he would have told the agents the truth about the conversations, it would have been the end of the inquiry.

"We'll still never know why a man with his background in intelligence, who knew that the FBI had the information, why he would not just say, 'Hey, yeah, I did it. I'm proud of it. It was within my authority. Next question.'"

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