materials in concluding that he was not required to file tax returns, that he was not required to pay income taxes, and that he could claim refunds of the money withheld from his pay. Cheek also contended that his wages from a private employer (American Airlines) did not constitute income under the internal revenue laws. Cheek argued that he therefore had acted without the "willfulness" that was required for a criminal tax conviction. Ignorance of law Under U.S. criminal law, the general rule is that ignorance of the law or a mistake of law is not a valid defense to criminal prosecution (see also Ignorantia juris non excusat). However, there are exceptions to that rule. Some U.S. criminal statutes provide for what are known as "specific intent" crimes, where ignorance of the law may be a valid defense. The federal criminal tax statutes are examples of statutes for specific intent crimes, where actual ignorance of the law is a valid defense. Erroneous jury instructions Cheek was convicted, but during the jury deliberations, the jury asked the trial judge for a clarification on the law. The judge instructed the jury that an "honest but unreasonable belief is not a defense, and does not negate willfulness." The trial court also instructed the jury that "[a]dvice or research resulting in the conclusion that wages of a privately employed person are not income or that the tax laws are unconstitutional is not objectively reasonable, and cannot serve as the basis for a good faith misunderstanding of the law defense." Appeals Cheek appealed his conviction to the United States Court of Appeals for the Seventh Circuit, which upheld the conviction. The United States Supreme Court issued a writ of certiorari to review the case. At the Court, Cheek contended that the trial court had erred by instructing the jury that a misunderstanding of the law had to be objectively reasonable to negate willfulness. Opinion of the Court In its judgment, the Court produced two essential holdings: A genuine, good faith belief that one is not violating the Federal tax law based on a misunderstanding caused by the complexity of the tax law (e.g., the complexity of the statute itself) is a defense to a charge of "willfulness", even though that belief is irrational or unreasonable. A belief that the Federal income tax is invalid or unconstitutional is not a misunderstanding caused by the complexity of