Rebecca Flitcraft (D) served on a federal jury in a criminal case and provided the lone acquittal vote that caused a mistrial. Federal investigators looking into charges of juror tampering discovered that Ds had not filed income tax returns for 1981 and 1982 and that they had filed withholding forms in 1982 claiming exemption from tax. Indictments followed under 26 U.S.C. § 7203 (willful failure to file returns) and § 7205 (willful filing of a false withholding exemption certificate). At trial, Ds admitted that their income was high enough to make them liable for tax and that they had signed the false withholding forms and failed to file returns. Ds disputed that they acted willfully in failing to file the taxes. Rebecca stated that she had trusted her husband, Robert when he told her that he had researched the question and that they owed no tax. Robert testified that he had read cases and articles that convinced him that his wages were not income, merely an even exchange of money for time. Robert testified that he believed that filing a federal income tax return was voluntary. He sought to introduce case law and documents, which he claimed were the basis for his beliefs. P objected. The judge refused to allow D to introduce the legal materials on which he claimed to have relied, but did allow him to testify about them orally. P introduced evidence that Robert had belonged to a tax protest group. Ds were found guilty before the magistrate judge and the district court affirmed. Ds appealed. Ds contend that the jury would have been more likely to believe that they had an honest but mistaken belief about income tax if the jury had seen the literature that Ds has researched with.