We granted certiorari in this case to consider the circumstances in which the Constitution requires that an indictment be dismissed because of delay between the commission of an offense and the initiation of prosecution.

* On March 6, 1975, respondent was indicted for possessing eight firearms stolen from the United States mails, and for dealing in firearms without a license. The offenses were alleged to have occurred between July 25 and August 31, 1973, more than 18 months before the indictment was filed. Respondent moved to dismiss the indictment due to the delay.

The District Court conducted a hearing on respondent's motion at which the respondent sought to prove that the delay was unnecessary and that it had prejudiced his defense. In an effort to establish the former proposition, respondent presented a Postal Inspector's report on his investigation that was prepared one month after the crimes were committed, and a stipulation concerning the post-report progress of the probe. The report stated, in brief, that within the first month of the investigation respondent had admitted to Government agents that he had possessed and then sold five of the stolen guns, and that the agents had developed strong evidence linking respondent to the remaining three weapons.1 The report also stated, however, that the agents had been unable to confirm or refute respondent's claim that he had found the guns in his car when he returned to it after visiting his son, a mail handler, at work.2 The stipulation into which the Assistant United States Attorney entered indicated that little additional information concerning the crimes was uncovered in the 17 months following the preparation of the Inspector's report.3

To establish prejudice to the defense, respondent testified that he had lost the testimony of two material witnesses due to the delay. The first witness, Tom Stewart, died more than a year after the alleged crimes occurred. At the hearing respondent claimed that Stewart had been his source for two or three of the guns. The second witness, respondent's brother, died in April 1974, eight months after the crimes were completed. Respondent testified that his brother was present when respondent called Stewart to secure the guns, and witnessed all of respondent's sales. Respondent did not state how the witnesses would have aided the defense had they been willing to testify.4

The Government made no systematic effort in the District Court to explain its long delay. The Assistant United States Attorney did expressly disagree, however, with defense counsel's suggestion that the investigation had ended after the Postal Inspector's report was prepared. App. 9-10. The prosecutor also stated that it was the Government's theory that respondent's son, who had access to the mail at the railroad terminal from which the guns were "possibly stolen," id., at 17, was responsible for the thefts, id., at 13.5 Finally, the prosecutor elicited somewhat cryptic testimony from the Postal Inspector indicating that the case "as to these particular weapons involves other individuals"; that information had been presented to a grand jury "in regard to this case other than . . . (on) the day of the indictment itself"; and that he had spoken to the prosecutors about the case on four or five occasions. Id., at 20.

Following the hearing, the District Court filed a brief opinion and order. The court found that by October 2, 1973, the date of the Postal Inspector's report, "the Government had all the information relating to defendant's alleged commission of the offenses charged against him," and that the 17-month delay before the case was presented to the grand jury "had not been explained or justified" and was "unnecessary and unreasonable." The court also found that "(a)s a result of the delay defendant has been prejudiced by reason of the death of Tom Stewart, a material witness on his behalf." Pet. for Cert. 14a. Accordingly, the court dismissed the indictment.

(1) The Government appealed to the United States Court of Appeals for the Eighth Circuit. In its brief the Government explained the months of inaction by stating:

"(T)here was a legitimate Government interest in keeping the investigation open in the instant case. The defendant's son worked for the Terminal Railroad and had access to mail. It was the Government's position that the son was responsible for the theft and therefore further investigation to establish this fact was important.

". . . Although the investigation did not continue on a full time basis, there was contact between the United States Attorney's office and the Postal Inspector's office throughout . . . and certain matters were brought before a Federal Grand Jury prior to the determination that the case should be presented for indictment . . . ." Brief for United States in No. 75-1852 (CA8), pp. 5-6.

The Court of Appeals accepted the Government's representation as to the motivation for the delay, but a majority of the court nevertheless affirmed the District Court's finding that the Government's actions were "unjustified, unnecessary, and unreasonable." 532 F.2d 59, 61 (1976). The majority also found that respondent had established that his defense had been impaired by the loss of Stewart's testimony because it understood respondent to contend that "were Stewart's testimony available it would support (respondent's) claim that he did not know that the guns were stolen from the United States mails." Ibid. The court therefore affirmed the District Court's dismissal of the three possession counts by a divided vote.6

We granted certiorari, 429 U.S. 884, 97 S.Ct. 233, 50 L.Ed.2d 164, and now reverse.7

(2, 3) In United States v. Marion, 404 U.S. 307, 92 S.Ct. 455, 30 L.Ed.2d 468 (1971), this Court considered the significance, for constitutional purposes, of a lengthy preindictment delay. We held that as far as the Speedy Trial Clause of the Sixth Amendment is concerned, such delay is wholly irrelevant, since our analysis of the language, history, and purposes of the Clause persuaded us that only "a formal indictment or information or else the actual restraints imposed by arrest and holding to answer a criminal charge . . . engage the particular protections" of that provision. Id., at 320, 92 S.Ct., at 463.8 We went on to note that statutes of limitations, which provide predictable, legislatively enacted limits on prosecutorial delay, provide " 'the primary guarantee, against bringing overly stale criminal charges.' " Id., at 322, 92 S.Ct., at 464, quoting United States v. Ewell, 383 U.S. 116, 122, 86 S.Ct. 773, 777, 15 L.Ed.2d 627 (1966). But we did acknowledge that the "statute of limitations does not fully define (defendants') rights with respect to the events occurring prior to indictment," 404 U.S., at 324, 92 S.Ct., at 465, and that the Due Process Clause has a limited role to play in protecting against oppressive delay.

(4) Respondent seems to argue that due process bars prosecution whenever a defendant suffers prejudice as a result of preindictment delay. To support that proposition respondent relies on the concluding sentence of the Court's opinion in Marion where, in remanding the case, we stated that "(e)vents of the trial may demonstrate actual prejudice, but at the present time appellees' due process claims are speculative and premature." Id., at 326, 92 S.Ct., at 466. But the quoted sentence establishes only that proof of actual prejudice makes a due process claim concrete and ripe for adjudication, not that it makes the claim automatically valid. Indeed, two pages earlier in the opinion we expressly rejected the argument respondent advances here:

"(W)e need not . . . determine when and in what circumstances actual prejudice resulting from preaccusation delays requires the dismissal of the prosecution. Actual prejudice to the defense of a criminal case may result from the shortest and most necessary delay; and no one suggests that every delay-caused detriment to a defendant's case should abort a criminal prosecution." Id., at 324-325, 92 S.Ct., at 465. (Footnotes omitted.)

Thus Marion makes clear that proof of prejudice is generally a necessary but not sufficient element of a due process claim, and that the due process inquiry must consider the reasons for the delay as well as the prejudice to the accused.

(5, 6) The Court of Appeals found that the sole reason for the delay here was "a hope on the part of the Government that others might be discovered who may have participated in the theft . . . ." 532 F.2d, at 61. It concluded that this hope did not justify the delay, and therefore affirmed the dismissal of the indictment. But the Due Process Clause does not permit courts to abort criminal prosecutions simply because they disagree with a prosecutor's judgment as to when to seek an indictment. Judges are not free, in defining "due process," to impose on law enforcement officials our "personal and private notions" of fairness and to "disregard the limits that bind judges in their judicial function." Rochin v. California, 342 U.S. 165, 170, 72 S.Ct. 205, 209, 96 L.Ed. 183 (1952). Our task is more circumscribed. We are to determine only whether the action complained of here, compelling respondent to stand trial after the Government delayed indictment to investigate further violates those "fundamental conceptions of justice which lie at the base of our civil and political institutions," Mooney v. Holohan, 294 U.S. 103, 112, 55 S.Ct. 340, 342, 79 L.Ed. 791 (1935), and which define "the community's sense of fair play and decency," Rochin v. California, supra, 342 U.S., at 173, 72 S.Ct. at 210. See also Ham v. South Carolina, 409 U.S. 524, 526, 93 S.Ct. 848, 850, 35 L.Ed.2d 46 (1973); Lisenba v. California, 314 U.S. 219, 236, 62 S.Ct. 280, 289, 86 L.Ed. 166 (1941); Hebert v. Louisiana, 272 U.S. 312, 316, 47 S.Ct. 103, 104, 71 L.Ed. 270 (1926); Hurtado v. California, 110 U.S. 516, 535, 4 S.Ct. 111, 120, 28 L.Ed. 232 (1884).

(7) It requires no extended argument to establish that prosecutors do not deviate from "fundamental conceptions of justice" when they defer seeking indictments until they have probable cause to believe an accused is guilty; indeed it is unprofessional conduct for a prosecutor to recommend an indictment on less than probable cause.9 It should be equally obvious that prosecutors are under no duty to file charges as soon as probable cause exists but before they are satisfied they will be able to establish the suspect's guilt beyond a reasonable doubt. To impose such a duty "would have a deleterious effect both upon the rights of the accused and upon the ability of society to protect itself," United States v. Ewell, supra, 383 U.S., at 120, 86 S.Ct., at 776. From the perspective of potential defendants, requiring prosecutions to commence when probable cause is established is undesirable because it would increase the likelihood of unwarranted charges being filed, and would add to the time during which defendants stand accused but untried.10 These costs are by no means insubstantial since, as we recognized in Marion, a formal accusation may "interfere with the defendant's liberty, . . . disrupt his employment, drain his financial resources, curtail his associations, subject him to public obloquy, and create anxiety in him, his family and his friends." 404 U.S., at 320, 92 S.Ct., at 463. From the perspective of law enforcement officials, a requirement of immediate prosecution upon probable cause is equally unacceptable because it could make obtaining proof of guilt beyond a reasonable doubt impossible by causing potentially fruitful sources of information to evaporate before they are fully exploited.11 And from the standpoint of the courts, such a requirement is unwise because it would cause scarce resources to be consumed on cases that prove to be insubstantial, or that involve only some of the responsible parties or some of the criminal acts.12 Thus, no one's interests would be well served by compelling prosecutors to initiate prosecutions as soon as they are legally entitled to do so.13

(8) It might be argued that once the Government has assembled sufficient evidence to prove guilt beyond a reasonable doubt, it should be constitutionally required to file charges promptly, even if its investigation of the entire criminal transaction is not complete. Adopting such a rule, however, would have many of the same consequences as adopting a rule requiring immediate prosecution upon probable cause.

First, compelling a prosecutor to file public charges as soon as the requisite proof has been developed against one participant on one charge would cause numerous problems in those cases in which a criminal transaction involves more than one person or more than one illegal act. In some instances, an immediate arrest or indictment would impair the prosecutor's ability to continue his investigation, thereby preventing society from bringing lawbreakers to justice. In other cases, the prosecutor would be able to obtain additional indictments despite an early prosecution, but the necessary result would be multiple trials involving a single set of facts. Such trials place needless burdens on defendants, law enforcement officials, and courts.

Second, insisting on immediate prosecution once sufficient evidence is developed to obtain a conviction would pressure prosecutors into resolving doubtful cases in favor of early and possibly unwarranted prosecutions. The determination of when the evidence available to the prosecution is sufficient to obtain a conviction is seldom clear-cut, and reasonable persons often will reach conflicting conclusions. In the instant case, for example, since respondent admitted possessing at least five of the firearms, the primary factual issue in dispute was whether respondent knew the guns were stolen as required by 18 U.S.C. § 1708. Not surprisingly, the Postal Inspector's report contained no direct evidence bearing on this issue. The decision whether to prosecute, therefore, required a necessarily subjective evaluation of the strength of the circumstantial evidence available and the credibility of respondent's denial. Even if a prosecutor concluded that the case was weak and further investigation appropriate, he would have no assurance that a reviewing court would agree. To avoid the risk that a subsequent indictment would be dismissed for preindictment delay, the prosecutor might feel constrained to file premature charges, with all the disadvantages that would entail.14

Finally, requiring the Government to make charging decisions immediately upon assembling evidence sufficient to establish guilt would preclude the Government from giving full consideration to the desirability of not prosecuting in particular cases. The decision to file criminal charges, with the awesome consequences it entails, requires consideration of a wide range of factors in addition to the strength of the Government's case, in order to determine whether prosecution would be in the public interest.15 Prosecutors often need more information than proof of a suspect's guilt, therefore, before deciding whether to seek an indictment. Again the instant case provides a useful illustration. Although proof of the identity of the mail thieves was not necessary to convict respondent of the possessory crimes with which he was charged, it might have been crucial in assessing respondent's culpability, as distinguished from his legal guilt. If, for example, further investigation were to show that respondent had no role in or advance knowledge of the theft and simply agreed, out of paternal loyalty, to help his son dispose of the guns once respondent discovered his son had stolen them, the United States Attorney might have decided not to prosecute, especially since at the time of the crime respondent was over 60 years old and had no prior criminal record.16 Requiring prosecution once the evidence of guilt is clear, however, could prevent a prosecutor from awaiting the information necessary for such a decision.

(9) We would be most reluctant to adopt a rule which would have these consequences absent a clear constitutional command to do so. We can find no such command in the Due Process Clause of the Fifth Amendment. In our view, investigative delay is fundamentally unlike delay undertaken by the Government solely "to gain tactical advantage over the accused," United States v. Marion, 404 U.S., at 324, 92 S.Ct., at 465, precisely because investigative delay is not so one-sided.17 Rather than deviating from elementary standards of "fair play and decency," a prosecutor abides by them if he refuses to seek indictments until he is completely satisfied that he should prosecute and will be able promptly to establish guilt beyond a reasonable doubt. Penalizing prosecutors who defer action for these reasons would subordinate the goal of "orderly expedition" to that of "mere speed," Smith v. United States, 360 U.S. 1, 10, 79 S.Ct. 991, 997, 3 L.Ed.2d 1041 (1959). This the Due Process Clause does not require. We therefore hold that to prosecute a defendant following investigative delay does not deprive him of due process, even if his defense might have been somewhat prejudiced by the lapse of time.

(10) In the present case, the Court of Appeals stated that the only reason the Government postponed action was to await the results of additional investigation. Although there is, unfortunately, no evidence concerning the reasons for the delay in the record, the court's "finding" is supported by the prosecutor's implicit representation to the District Court, and explicit representation to the Court of Appeals, that the investigation continued during the time that the Government deferred taking action against respondent. The finding is, moreover, buttressed by the Government's repeated assertions in its petition for certiorari, its brief, and its oral argument in 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." Pet. for Cert. 14.18 We must assume that these statements by counsel have been made in good faith. In light of this explanation, it follows that compelling respondent to stand trial would not be fundamentally unfair. The Court of Appeals therefore erred in affirming the District Court's decision dismissing the indictment.

(11) In Marion we conceded that we could not determine in the abstract the circumstances in which preaccusation delay would require dismissing prosecutions. 404 U.S., at 324, 92 S.Ct., at 465. More than five years later, that statement remains true. Indeed, in the intervening years so few defendants have established that they were prejudiced by delay that neither this Court nor any lower court has had a sustained opportunity to consider the constitutional significance of various reasons for delay.19 We therefore leave to the lower courts, in the first instance, the task of applying the settled principles of due process that we have discussed to the particular circumstances of individual cases. We simply hold that in this case the lower courts erred in dismissing the indictment.

Reversed.

Mr. Justice STEVENS, dissenting.

If the record presented the question which the Court decides today, I would join its well-reasoned opinion. I am unable to 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 majority 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, 90 S.Ct. 1598, 1608, n. 16, 26 L.Ed.2d 142. 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 whatsoever to a prompt hearing." Moody v. Daggett, 429 U.S. 78, 91, 97 S.Ct. 274, 281, 50 L.Ed.2d 236 (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, 97 S.Ct., at 281. 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.