such as tax crimes, is a purely legal question that is not to be submitted to the jury. See United States v. Klausner, 80 F.3d 55, 61 (2d Cir.1996) (distinguishing materiality in Gaudin as a mixed law and fact issue). Assuming the duty to disclose is an element of concealment to be charged to the jury under § 1001, the district court’s refusal to use Blackley’s proposed charge would still not be reversible. Under circuit law, the absence of a jury instruction on an element of the crime is not reversible error where it is inconceivable that the jury could have found the defendant guilty of the crime without making a finding as to the omitted element. See United States v. Winstead, 74 F.3d 1313, 1321 (D.C.Cir.1996); see also United States v. Parmelee, 42 F.3d 387, 393 (7th Cir.1994) (<HOLDING>); Redding v. Benson, 739 F.2d 1360, 1363-64
holding modified categorical approach unavailable where the statute of conviction was missing an element of the generic definition holding that when the jury finds facts that are so closely related to the omitted element that no rational jury could find those facts without also finding the omitted element this exercise amounts to the functional equivalent of the omitted element holding that instructional error on missing element is harmless if no rational jury could have found the defendant  guilty of violating the statute without also making the proper finding as to the missing element holding that error is not harmless if the defendant contested the omitted element and raised evidence to support a contrary finding holding that an instructional error is harmless if no rational jury could have made its findings without also finding the omitted  fact to be true