A defendant’s duress defense does not controvert elements of a crime. The government bore the burden of proving beyond a reasonable doubt that defendant knew that she was making false statements and knew that she was breaking the law when she violated federal law by acquiring a firearm while under federal indictment and making false statements in order to acquire the weapon. Since the defendant testified that she knew the statements were false, the government met its burden. She contended that she did so under duress because her boyfriend threatened her and her daughter. The Court concluded that the existence of duress does not normally controvert any of the elements of the offense itself. Further, modern common law does not require the government to bear the burden of disproving her duress defense beyond a reasonable doubt. The long-established common-law rule, which places the burden of proving that defense on the defendant, was not upset by Davis v. U.S. (which held that a defendant’s insanity controverted the necessary mens rea for murder).