The petition for writ of certiorari to the United States Court of Appeals for the District of Columbia Circuit is granted. Charged in a three-count indictment for violation of R. S. § 102, as amended, 2 U. S. C. § 192, for failure to answer three questions put to him by a subcommittee of the Internal Security Subcommittee of the Senate Committee on the Judiciary, the petitioner, having waived *577trial by jury, was found guilty on all counts and sentenced to six months’ imprisonment and to pay a fine of $1,000. After the sentence was sustained by the Court of Appeals, 99 U. S. App. D. C. 360, 240 F. 2d 46, this Court, having granted a petition for certiorari, remanded the case, 354 U. S. 930, to the Court of Appeals for reconsideration in light of Watkins v. United States, 354 U. S. 178. On reargument before the Court of Appeals sitting en banc, a divided court again affirmed the conviction. 102 U. S. App. D. C. 264, 252 F. 2d 828.
The broad scope of authority vested in Congress to conduct investigations as an incident to the “legislative Powers” granted by the Constitution is not questioned. See Watkins v. United States, supra, at 215. But when Congress seeks to enforce its investigating authority through the criminal process administered by the federal judiciary, the safeguards of criminal justice become operative. The subject matter of inquiry before the subcommittee at which petitioner appeared as a witness concerned the recantation of prior testimony by a witness named Matusow. In the course of the hearing, the questioning of petitioner entered upon a “brief excursion,” 99 U. S. App. D. C. 360, 367, 240 F. 2d 46, 53, into proposed legislation barring Communists from practice at the federal bar, a subject not within the subcommittee’s scope of inquiry as authorized by its parent committee. Inasmuch as petitioner’s refusal to answer related to questions not clearly pertinent to the subject on which the two-member subcommittee conducting the hearing had been authorized to take testimony, the conditions necessary to sustain a conviction for deliberately refusing to answer questions pertinent to the authorized subject matter of a congressional hearing are wanting. Watkins v. United States, supra. The judgment of the *578Court of Appeals is therefore reversed and the cause remanded to the District Court with directions to dismiss the indictment.
Reversed.
Mr. Justice Burton took no part in the consideration or decision of this case.