Stupid has never been a defense for a crime, and negligence is even actionable under civil laws. Criminal laws (to my knowledge) imply negligence from the outset - that's why they are freaking criminal. You don't have to prove that a person was negligent in their actions if they are caught driving drunk, just prove they were drunk - the negligence is implied...
This guy just admitted that he was too stupid to follow the rules the rest of us have to follow, and that he was negligent of his legal responsibilities. Civil or criminal - case closed.
Congressionally - well that's another matter, they don't seem to operate by the same legal standards that they place upon the rest of us...
Reelection as a dimocrat from Harlem is in his future then.