Costello (D), was indicted for wilfully attempting to evade payment of income taxes. D falsely and fraudulently reported less income than he and his wife actually received during the taxable years in question. D promptly filed a motion for inspection of the minutes of the grand jury and a dismissal of the indictment. His motion was based on an affidavit stating that he was firmly convinced there could have been no legal or competent evidence before the grand jury which indicted him since he had reported all his income and paid all taxes due. The motion was denied. At trial, the Government (P) offered evidence designed to show increases in D's net worth in an attempt to prove that he had received more income during the years in question than he had reported. P called and examined 144 witnesses and introduced 368 exhibits. Three government agents summarized the vast amount of evidence and introduced computations showing, D and his wife had received far greater income than they had reported. Through cross-examination, D developed the fact that the three investigating officers had been the only witnesses before the grand jury. D moved to dismiss the indictment on the ground that the only evidence before the grand jury was 'hearsay,' since the three officers had no firsthand knowledge of the transactions upon which their computations were based. The trial court refused to dismiss the indictment. D was convicted. The Court of Appeals affirmed, holding that the indictment was valid even though the sole evidence before the grand jury was hearsay. The Supreme Court granted certiorari.