WATCH: Judiciary Democrat reveals Trump's son invented new legal theory in testimony to Congress

During closed-door testimony before Congress, President Donald Trump's eldest son attempted to invoke a novel legal doctrine, a member of the House Judiciary Committee revealed to MSNBC's Lawrence O'Donnell on Monday.

Rep. Eric Swalwell (D-CA) sits on both the House Judiciary Committee and House Permanent Select Committee on Intelligence.

"There's some questions about the communications with his father and about the meeting at Trump Tower," O'Donnell noted. "Do you believe Donald Trump, Jr. lied to your committee?"

"I think he showed a consciousness of guilt, when he was asked about conversations he had with his father, whether on not he told his father about that meeting he took where the Russians were offering dirt on Hillary Clinton," Swalwell replied.

"He told us he's not going to answer any questions with his father, asserting a father-son privilege," he explained. "Which is privileged privilege -- only something that the Trumps could create."

"I think innocent people would have been straight with us, Don Jr. didn't want to be straight," he concluded. "Bob Mueller will know the answer to that."

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