Shillitani (D) appeared under subpoena before a grand jury investigating possible violations of the federal narcotics laws. On three occasions, he refused to answer questions, invoking his privilege against self-incrimination. At the Government's request, the District Judge then granted him immunity under the Narcotic Control Act of 1956, 18 U.S.C. 1406 (1964 ed.), and ordered him to answer certain questions. D persisted in his refusal. Thereafter, in a proceeding under Rule 42 (b) of the Federal Rules of Criminal Procedure, the District Court found him guilty of criminal contempt. No jury trial was requested. D was sentenced to prison for two years 'or until the further order of this Court. Should . . . Mr. Shillitani answer those questions before the expiration of said sentence, or the discharge of the said grand jury, whichever may first occur, the further order of this Court may be made terminating the sentence of imprisonment.' The Court of Appeals affirmed; 'sentence contained a purge clause.' It further construed the sentence as giving Shillitani an unqualified right to be released if and when he obeyed the order to testify. Pappadio (D1) appeared under subpoena before the same grand jury. He also refused three times to answer numerous questions on the ground that the answers would incriminate him. He was then granted immunity under 18 U.S.C. 1406 and directed to testify. He continued to refuse to answer any questions except those of identification. D refused to answer five questions pertaining to his alleged association with a group headed by Thomas Lucchese which engaged in narcotics traffic and other illicit activities. D1's demand for a jury was denied, and the District Court found him in contempt for willful disobedience of its order to testify. He received a sentence almost identical to that given D, and the Court of Appeals affirmed on the same grounds.