delivered the opinion of the Court.
In March of 1947, the Committee on Education and Labor was, as it is now, a standing committee of the House of Representatives.1 During the first session of the 80th Congress it held frequent hearings on proposed amendments to the National Labor Relations Act. On March 1, 1947, petitioner appeared as a witness before the committee, under oath, and in the course of the proceedings was asked a series of questions directed to his political affiliations and associations. In his answers he unequivocally denied that he was a Communist or that he endorsed, supported or participated in Communist programs. As a result of these answers he was indicted for perjury under § 22-2501 of the District of Columbia Code,2 and after a trial by jury was convicted. The Court of Appeals affirmed the conviction, 84 U. S. App. D. C. 132, 171 F. 2d 1004, and we granted certiorari to review its validity. 336 U. S. 934.
No question is raised as to the relevancy or propriety of the questions asked. Petitioner’s main contention is that the committee was not a “competent tribunal” within the meaning of the statute, in that a quorum of *86the committee was not present at the time of the incident on which the indictment was based. As to this, the record reveals the following: the Committee on Education and Labor consists of twenty-five members, of whom thirteen constitute a quorum. At the commencement of the afternoon session on Saturday, March 1, 1947, shortly after two o’clock, a roll call showed that fourteen members were present. Petitioner’s testimony started some time after four o’clock. The responses said to constitute offenses were given just prior to five p. m.
Evidence was adduced at the trial from which a jury might have concluded that at the time of the allegedly perjurious answers less than a quorum — as few as six— of the committee were in attendance. Counsel for the petitioner contended vigorously at the trial, on appeal and in this Court that unless a quorum were found to be actually present when the crucial questions were asked, the statutory requirement of a competent tribunal was not met and that absent such a finding a verdict of acquittal should follow.
The trial court agreed that the presence of a quorum was an indispensable part of the offense charged, and instructed the jury that to find the defendant guilty they had to find beyond a reasonable doubt “That the defendant Christoffel appeared before a quorum of at least thirteen members of the said Committee,” and that “at least that number must have been actually and physically present .... If such a Committee so met, that is, if 13 members did meet at the beginning of the afternoon session of March 1, 1947, and thereafter during the progress of the hearing some of them left temporarily or otherwise and no question was raised as to the lack of a quorum, then the fact that the majority did not remain there would not affect, for the purposes of this case, the existence of that Committee as a competent tribunal provided that before the oath was administered *87and before the testimony of the defendant was given there were present as many as 13 members of that Committee at the beginning of the afternoon session. . . .”
This charge is objected to insofar as it allows the jury to find a quorum present simply by finding that thirteen or more members were in attendance when the committee was convened, without reference to subsequent facts.
The Constitution of the United States provides that “Each House may determine the Rules of its Proceedings,” Art. I, § 5, Cl. 2, and we find that the subject of competency, both of the House as a whole and of its committees, has been a matter of careful consideration. Rule XI (2) (f) of the House of Representatives reads in part, “The rules of the House are hereby made the rules of its standing committees so far as applicable . . . .” Rule XV of the House provides for a call of the House if a quorum is not present, and it has been held under this rule that such a call, or a motion to adjourn, is the only business that may be transacted in the absence of a quorum. IV Hind’s Precedents § 2950; id. § 2988. See id. § § 2934, 2939; VI Cannon’s Precedents § 653; id. § 680. It appears to us plain that even the most highly privileged business must be suspended in the absence of a quorum in the House itself.
A similar situation obtains in the committees.3 The Legislative Reorganization Act of 1946, 60 Stat. 812, 831, provides, referring to the standing committees, in § 133 (d), “No measure or recommendation shall be reported from any such committee unless a majority of the commit*88tee were actually present.” The rule embodied in this subsection was effective as long ago as 1918 to keep off the floor of the House a bill from a committee attended by less than a quorum, even though no objection was raised in the committee meeting itself. It appeared that the situation in the committee was much like the one with which we are concerned, with members coming and going during the meeting. No point of no quorum was raised at the committee meeting. When the Chairman proposed in the House to bring up the bill considered in the meeting, the Speaker ruled, on objection being made from the floor, that in spite of the point’s not having been raised in committee, the bill could not be reported. The absence of a quorum of the committee, though at the time unobjected to, had made effective action impossible. VIII Cannon’s Precedents § 2212. Witnesses in committee hearings cannot be required to be familiar with the complications of parliamentary practice. Even if they are, the power to raise a point of no quorum appears to be limited to members of the committee. We have no doubt that if a member of the committee had raised a point of no quorum and a count had revealed the presence of less than a majority, proceedings would have been suspended until the deficiency should be supplied. In a criminal case affecting the rights of one not a member, the occasion of trial is an appropriate one for petitioner to raise the question.
Congressional practice in the transaction of ordinary legislative business is of course none of our concern, and by the same token the considerations which may lead Congress as a matter of legislative practice to treat as valid the conduct of its committees do not control the issue before us. The question is neither what rules Congress may establish for its own governance, nor whether presumptions of continuity may protect the validity of its legislative conduct. The question is rather what rules *89the House has established and whether they have been followed. It of course has the power to define what tribunal is competent to exact testimony and the conditions that establish its competency to do so. The heart of this case is that by the charge that was given it the jury was allowed to assume that the conditions of competency were satisfied even though the basis in fact was not established and in face of a possible finding that the facts contradicted the assumption.
We are measuring a conviction of crime by the statute which defined it. As a consequence of this conviction, petitioner was sentenced to imprisonment for a term of from two to six years. An essential part of a procedure which can be said fairly to inflict such a punishment is that all the elements of the crime charged shall be proved beyond a reasonable doubt. An element of the crime charged in the instant indictment is the presence of a competent tribunal, and the trial court properly so instructed the jury. The House insists that to be such a tribunal a committee must consist of a quorum, and we agree with the trial court’s charge that, to convict, the jury had to be satisfied beyond a reasonable doubt that there were “actually and physically present” a majority of the committee.4
*90Then to charge, however, that such requirement is satisfied by a finding that there was a majority present two or three hours before the defendant offered his testimony, in the face of evidence indicating the contrary, is to rule as a matter of law that a quorum need not be present when the offense is committed. This not only seems to us contrary to the rules and practice of the Congress but denies petitioner a fundamental right. That right is that he be convicted of crime only on proof of all the elements of the crime charged against him. A tribunal that is not competent is no tribunal, and it is unthinkable that such a body can be the instrument of criminal conviction. The Court of Appeals erred in affirming so much of the instructions to the jury as allowed them to find a quorum present without reference to the facts at the time of the alleged perjurious testimony, and its judgment is reversed.
Reversed.
Legislative Reorganization Act of 1946, 60 Stat. 812, § 121; Rule X, House of Representatives; H. R. Res. No. 111, 80th Cong., 1st Sess., adopted Feb. 26, 1947 (93 Cong. Rec. 1457).
“§ 22-2501 .... Perjury — Subornation of perjury. Every person who, having taken an oath or affirmation before a competent tribunal, officer, or person, in any case in which the law authorized such oath or affirmation to be administered, that he will testify, declare, depose, or certify truly, or that any written testimony, declaration, deposition, or certificate by him subscribed is true, wilfully and contrary to such oath or affirmation states or subscribes any material matter which he does not believe to be true, shall be guilty of perjury; and any person convicted of perjury or subornation of perjury shall be punished by imprisonment in the penitentiary for not less than two nor more than ten years. . . .” 31 Stat. 1329.
There is some difference between procedure in the full House and in its committees. In the former, business is transacted on the assumption that a quorum is present at all times, unless a roll call or a division indicate the contrary. In committee meetings, however, the presence of a quorum must be affirmatively shown before the committee is deemed to be legally met. VIII Cannon’s Precedents § 2222.
In Meyers v. United States, 84 U. S. App. D. C. 101, 171 F. 2d 800, the appellant made contentions similar to those of petitioner. The Court of Appeals for the District of Columbia Circuit held the same view expressed here. “On October 6, 1947, however, only two senators were present at the hearing. Since they were a minority of the subcommittee, they could not legally function except to adjourn. For that reason, the testimony of Lamarre given on that day cannot be considered as perjury nor can appellant be convicted of suborning it.” 84 U. S. App. D. C. at 112, 171 F. 2d at 811. The conviction was affirmed on the ground that all the perjurious statements alleged in the indictment were made on October 4, when a quorum was present. 84 U. S. App. D. C. at 113, 171 F. 2d at 812.