In a criminal trial of a board-certified dermatologist indicted for executing a "scheme or artifice to defraud" when billing public and private healthcare benefit programs, 18 U.S.C. section 1344, the government's interlocutory appeal under section 3731 challenging the district court's grant of defendant's motions to exclude certain evidence is granted where the district court's rulings unduly the latitude reasonably necessary for the government to carry its burden of proof.