Record contained sufficient evidence to support jury’s guilty verdict on charges that defendants conspired to defraud U.S. by impeding IRS, as well as on charges of mail fraud, wire fraud, and assisting others to file false tax returns arising out of defendants’ marketing and administration of trust system by which customers unlawfully diverted taxable income into various trusts in attempt to avoid income taxes. Govt. showed that defendants were aware that instant trust system was sham, and that Dist. Ct. did not err in barring defendants from establishing that trust system was legal means of tax avoidance. Ct. further rejected defendants’ claim that Dist. Ct.improperly allowed govt. to show, through exhibits including adverse IRS notices, ADRC disbarment proceedings and adverse court rulings, defendants’ notice that trust system was unlawful while precluding defendants from establishing any subjective belief that trust system was lawful. Ct. also rejected defendants’ contention that Dist. Ct. harbored bias against defendants by: (1) appointing substitute counsel for one defendant whose hired counsel was ill during trial; (2) harshly questioning one defense counsel with respect to merits of pre-trial motion; (3) expressed skepticism with respect to testimony of one witness offering favorable testimony to defendants; (4) expressed impatience with length of time counsel spent on direct examination of his client; and (5) improperly prompted objections from prosecutor and sustained own objections to questioning by defense counsel.