How can lies be allowed at a congressional hearing?

Tucker Carlson pointed out that Officer Harry Dunn lied during day one of the Jan. 6th committee hearings by saying that Officer Brian Sicknick died due to the rioters. The D.C. medical examiner said that Brian Sicknick died due to natural causes. The first day of the Jan. 6th hearings was a disaster. How can lies be allowed to be told at a congressional hearing?