lying to Congress is a serious crime

As you might’ve heard, Congress is investigating the possibility that baseball pitcher Roger Clemens lied to them under oath about his use of steroids.  Representative Henry Waxman, then the committee’s chairman, said perjury and false statements “are serious crimes that undermine the ability of Congress to perform its duties.”  True… but at the same time, I keep trying to imagine how a politician can accuse anyone of lying with a straight face, and I just can’t do it.  I mean, how many members of Congress have knowingly lied while on the job?  (I don’t think I want to know the statistics, because it would probably be very depressing.)