Contempt of Congress
"Contempt of Congress is defined in statute, 2 U.S.C.A. § 192, enacted in 1938, which states that any person who is summoned before Congress who "willfully makes default, or who, having appeared, refuses to answer any question pertinent to the question under inquiry" shall be guilty of a misdemeanor and subject to a maximum $1,000 fine and 12 month imprisonment." 
While this statute is phrased as an unconditional obligation, the Fifth Amendment takes precedence over it. For this reason, many witnesses called to testify at Congressional hearings plead the Fifth Amendment and refuse to testify.