dissenting.
If the record presented the question which the Court decides today, I would join its well-reasoned opinion. I am unable *798to do so because I believe our review should be limited to the facts disclosed by the record developed in the District Court and the traditional scope of review we have exercised with regard to issues of fact.
After a thorough hearing on the respondent’s motion to dismiss the indictment for prejudicial preindictment delay— a hearing at which both sides were given every opportunity to submit evidence concerning the question- — -the District Court found that “[t]he Government’s delay ha[d] not been explained or justified and [was] unnecessary and unreasonable.” On appeal, the Court of Appeals concurred, noting that the District Court’s determination was “supported by the evidence.” 532 F. 2d 59, 60-61 (CA8 1976). These concurrent findings of fact make it improper, in my judgment, for this Court to make its own determination that “the Government postponed action ... to await the results of additional investigation,” ante, at 796.1
That determination is not supported by the record.2 The *799majority opinion correctly points out that there was “no evidence concerning the reasons for delay in the record,” and yet proceeds to accept as fact the representations in the Government’s briefs to the Court of Appeals and to this Court that “ 'the delay was caused by the government’s efforts to identify persons in addition to respondent who may have participated in the offenses.’ ” Ibid. This finding of a continuing investigation, which forms the foundation of the majority opinion, comes from statements of counsel made during the appellate process. As we have said of other unsworn statements which were not part of the record and therefore could not have been considered by the trial court: “Manifestly, [such statements] cannot be properly considered by us in the disposition of [a] case.” Adickes v. Kress & Co., 398 U. S. 144, 157-158, n. 16. While I do not question the good faith of Government counsel, it is not the business of appellate courts to make decisions on the basis of unsworn matter not incorporated in a formal record.
The findings of the District Court, as approved by the Court of Appeals, establish four relevant propositions: (1) this is a routine prosecution; (2) after the Government assembled all of the evidence on which it expects to establish respondent’s guilt, it waited almost 18 months to seek an indictment; (3) the delay was prejudicial to respondent’s defense; and (4) no reason whatsoever explains the delay. We may reasonably infer that the prosecutor was merely busy with other matters that he considered more important than this case.
The question presented by those facts is not an easy one. Nevertheless, unless we are to conclude that the Constitution imposes no constraints on the prosecutor’s power to postpone the filing of formal charges to suit his own convenience, I believe we must affirm the judgment of the Court of Appeals. A contrary position “can be tenable only if one assumes that the constitutional right to a fair hearing includes no right *800whatsoever to a prompt hearing.” Moody v. Daggett, 429 U. S. 78, 91 (Stevens, J., dissenting). The requirement of speedy justice has been part of the Anglo-American common-law tradition since the Magna Carta. See id., at 92 n. 5. It came to this country and was embodied in the early state constitutions, see the Massachusetts Constitution of 1780, Part I, Art. XI, and later in the Sixth Amendment to the United States Constitution. As applied to this case, in which respondent made numerous anxious inquiries of the Postal Inspectors concerning whether he would be indicted, in which the delay caused substantial prejudice to the respondent, and in which the Government has offered no justification for the delay, the right to speedy justice should be honored.
If that right is not honored in a case of this kind, the basic values which the Framers intended to protect by the Sixth Amendment’s guarantee of a speedy trial, and which motivated Congress to enact the Speedy Trial Act of 1974, will become nothing more than managerial considerations for the prosecutor to manipulate.
I respectfully dissent.
It is a settled rule of this Court that we will not review concurrent findings of fact by two courts “ 'in the absence of a very obvious and exceptional showing of error.’ ” Berenyi v. Immigration Director, 385 U. S. 630, 635, citing Graver Mfg. Co. v. Linde Co., 336 U. S. 271, 275. Mr. Justice Jackson has called this a “seasoned and wise rule . . . .” Comstock v. Group of Investors, 335 U. S. 211, 214.
An examination of the transcript of the District Court hearing reveals that the Government produced no evidence as to why the indictment was delayed. The Government stipulated that it proceeded before the grand jury only on evidence collected some 17 months before the presentation and that no additional evidence had caused it to proceed. Although the Court of Appeals surmised that “[n]o reason existed for the delay except a hope on the part of the Government that others might be discovered who may have participated in the theft[s) . . . ,” 532 F. 2d, at 61, even this assumption is not borne out by the record o-f the District Court hearing. Although not under oath, the prosecuting attorney indicated that the Government theorized that the guns in question came from the respondent’s son, who worked at a freight terminal and would have had access to the mails. Yet even this theory was never shown to be the cause of the delay. Not even the prosecuting attorney stated as much.