One of the process crimes that has caught many otherwise law abiding folks is 18 USC § 1001 which makes it a crime to knowingly falsify, conceal, or cover up by any trick, scheme, or device a material fact when dealing with the federal government. Section (c)(2) of the law says that it applies to
any investigation or review, conducted pursuant to the authority of any committee, subcommittee, commission or office of the Congress …
So, Gentle Reader, if you lied to a House committee, you could be prosecuted, convicted, and sent to jail for five years.
OTOH, if you were a member of Congress acting in your official capacity at a committee hearing, you would might claim that your lying was protected by the Speech or Debate Clause of the Constitution. While a congresscritter’s immunity with respect to a civil tort (eg., a defamation suit) is settled law, the courts didn’t find that protection in the Speech or Debate Clause. It stems from the Westfall Act, a federal statute that grants all federal employees absolute immunity from common-law tort claims arising out of acts they undertake in the course of their official duties.
AFAIK, a lie told by a congresscirtter in the context of a committee hearing has never resulted in a criminal referral, and immunity to 18 USC § 1001 or § 1621 (Perjury) under the Speech or Debate Clause has never been tested. IMHO, Adam Schiff’s clearly false statement during the House Impeachment Hoax hearing yesterday that he did not know the identity of the Whistleblower would make an excellent test case, but I doubt he will even be censured for his unethical behavior.
Lying liars gott lie.