dissenting.
The Court concedes that federal prosecutors violated Rule 6(d) of the Federal Rules of Criminal Procedure in presenting their case against defendants Mechanik and Lili to the grand jury. The Court holds, however, that because defendants were ultimately convicted of some of the counts against them, “any error in the grand jury proceeding connected with the charging decision was harmless beyond a reasonable doubt.” Ante, at 70. Because I believe that the majority’s rule misconceives the role both of the grand jury and of the harmless-error doctrine, I dissent.
I — !
The Court s decision today renders Rule 6(d) almost unenforceable. As the facts of this litigation demonstrate, Rule 6(d) violations are difficult for defendants to uncover. The grand jury conducts its investigation in secret, aided only by the prosecutors and witnesses. United States v. Calandra, 414 U. S. 338, 343 (1974). Defendants are not entitled to grand jury transcripts before trial; due to the strictly enforced tradition of grand jury secrecy, defendants generally have access to no information whatsoever regarding the conduct of the grand jury proceedings. See M. Frankel & G. Naftalis, The Grand Jury 81-89 (1977). Requests by defendants pursuant to Rule 6(e)(3)(C)(ii) for disclosure of grand jury materials, “upon a showing that grounds may exist for a motion to dismiss the indictment because of matters occurring before the grand jury,” are rarely granted; a defendant often can make the necessary showing only with the aid of the materials he seeks to discover. See 1 C. Wright, Federal Practice and Procedure § 108, pp. 263-265 (2d ed. 1982). Defendants’ only access to grand jury materials is likely to be through the medium of the Jencks Act, 18 U. S. C. § 3500, which requires the prosecutor, after direct examination of a Government witness, to produce the witness’ prior statements. That disclosure, however, does not *81take place until after trial has begun, and then only on a piecemeal and incomplete basis.
There is thus little likelihood that a defendant can raise a substantial claim under Rule 6(d) before his trial begins. After the start of trial, overwork and the press of events may prevent the district judge from disposing of a newly raised Rule 6(d) claim. The most attractive course for the district judge will be to defer a ruling until the close of trial, the course ultimately followed in this case. Indeed, the district judge may not have the opportunity to rule until that time. Under today’s decision, however, deferring a meritorious Rule 6(d) claim until the close of trial disposes of it permanently. If the movant is acquitted, then his Rule 6(d) motion is moot; if the movant is convicted, under the majority’s reasoning, then any error was harmless. The Court’s decision thus offers busy district judges a new and unique way to reduce their workload; one need not believe in a judicial conspiracy against the assertion of Rule 6(d) rights to suspect that district judges, faced with Rule 6(d) motions necessarily raised in the middle of trial, will follow the Court’s invitation.
Should a district judge decide a Rule 6(d) motion during trial, the majority’s scheme insulates that ruling from appellate review. Appeal before judgment is unlikely; the Court has never allowed immediate appeal of an order issued after the start of a criminal trial. See Flanagan v. United States, 465 U. S. 259, 269 (1984).1 And under the decision today, *82such rulings cannot be appealed after judgment. Enforcement of Rule 6(d) is thus left to the unreviewable largesse of the district court.
II
A
We have no reason to believe that Congress intended Rule 6(d) to have so little practical meaning. The legislative history of Rule 6, indeed, belies that approach. In 1933, Congress was faced with “a conflict of legal decision as to the right, under existing law, to permit stenographers in grand jury rooms without invalidating the subsequent conviction of defendant.” S. Rep. No. 64, 73d Cong., 1st Sess., 1 (1933). It responded by adding a narrow clause to the harmless-error statute, Rev. Stat. § 1025 (later codified as 18 U. S. C. § 556 (1946 ed.)), providing that no indictment should be found insufficient, or conviction be reversed, because of the presence of stenographers in the grand jury room. But Congress nowhere expressed disagreement with the general proposition that the presence of an unauthorized person in the grand jury room invalidates a subsequent conviction. E. g., United States v. Fall, 56 App. D. C. 83, 84, 10 F. 2d 648, 649 (1925); Latham v. United States, 226 F. 420, 424 (CA5 1915).
More recently, Congress amended Rule 6 in 1972 to incorporate by reference the provisions of the Jury Selection and Service Act of 1968; it provided that a defendant may move to dismiss the indictment based on the Government’s failure to comply with that Act in the selection of the grand jury array or of individual grand jurors. Fed. Rule Crim. Proc. 6(b)(2). The advisory notes expressly state that the district judge may rule on such a challenge to the grand jury either before or after the verdict. Advisory Committee Notes on Fed. Rule Crim. Proc. 6, 18 U. S. C. App., p. 568 (1972 amendment). There is no hint that Congress, in providing for a *83ruling after the verdict, intended that ruling to be a mere intellectual exercise.
B
The majority’s opinion misconceives the role of harmless-error analysis. We have recognized that harmless-error doctrine, denying any remedy in cases of clear prosecutorial misconduct, “can work very unfair and mischievous results.” Chapman v. California, 386 U. S. 18, 22 (1967). Denying defendants relief for clear violations of their procedural rights reduces the law to “‘pretend-rules,’” United States v. Borello, 766 F. 2d 46, 58 (CA2 1985), quoting United States v. Antonelli Fireworks Co., 155 F. 2d 631, 661 (CA2) (Frank, J., dissenting), cert. denied, 329 U. S. 742 (1946); it means that prosecutors are free to engage in prohibited conduct subject only to “purely ceremonial” words of appellate displeasure. 155 F. 2d, at 661.
The Court’s rule that all grand jury misconduct becomes harmless after conviction, however, is especially pernicious. Contrary to the majority’s suggestion that reversal is too costly a remedy for grand jury misconduct, ante, at 72, it is the majority’s refusal to reverse convictions for demonstrated grand jury misconduct that imposes unacceptable costs. There are few limitations on the conduct of the prosecutor before the grand jury. Those limitations are found only in Federal Rule of Criminal Procedure 6, the text of which takes up little more than a page in the official compilation of United States laws. Violations of even those isolated restrictions, in by far the majority of cases, will go undetected by defendants. The only way to allow even minimally effective enforcement of those rules is to reverse the convictions of defendants whose indictments were tainted by Rule 6 violations.
Such an approach would not hamper the enforcement of the criminal law. Violations of Rule 6(d) will be nonexistent if the prosecutor exercises proper control over access to the grand jury chambers. The substantive law is not onerous or *84ambiguous, and most violations are the product of the prosecutor’s failure to adopt safeguards to ensure compliance. See 2 W. LaFave & J. Israel, Criminal Procedure §15.6, p. 333 (1984). There is no danger of a prosecutor slipping into an inadvertent Rule 6(d) violation comparable to that, say, of making an ill-worded remark in the heat of trial. Courts would not often have cause to reverse convictions because of Rule 6(d) violations.
The majority’s goal of upholding criminal convictions not marred by substantial defect does not justify reducing Congress’ command regarding the proper conduct of grand jury proceedings to a mere form of words, without practical effect. Respect for the rule of law demands that improperly procured indictments be quashed even after conviction, because “only by upsetting convictions so obtained can the ardor of prosecuting officials be kept within legal bounds and justice be secured; for in modern times all prosecution is in the hands of officials.” United States v. Remington, 208 F. 2d 567, 574 (CA2 1953) (L. Hand, J., dissenting).2
*85H-i HH
The opinion concurring in the judgment suggests that the Rule 6(d) violation in this litigation should be viewed as harmless on the theory that the grand jury would have returned the same indictment regardless of the prosecutor’s misconduct. Under that approach, a district court faced with a Rule 6(d) violation should examine the grand jury transcripts in an attempt to divine the effect of the violation on the jury’s charging decision, and allow the indictment or conviction to stand only if it finds that there was no such effect. Such a rule would be contrary to the traditional black-letter law that “[a]ny violation of Rule 6(d) is per se prejudicial to the defendant and will result in dismissal of the indictment,” 8 J. Moore, Federal Practice ¶6.04[7], p. 6-91 (2d ed. 1985).3 I believe that such an approach would be unworkable and would undermine the limits Congress imposed on the conduct of grand jury investigations.
Many of the reasons given above for rejecting the majority’s view that grand jury impropriety is always harmless *86once a verdict is reached, apply in this context as well. Given defendants’ difficulty in discovering Rule 6(d) violations, it is all the more important that dismissal of the indictment be certain when violations of the Rule are found. Only such a sanction can come close to providing prosecutors with an incentive to obey the Rule’s commands. See United States v. Pignatiello, 582 F. Supp. 251, 255 (Colo.1984).
Such harmless-error analysis, moreover, overlooks the practical impossibility of determining the effect of a Rule 6(d) violation. The prejudicial impact of the unauthorized presence of persons in the grand jury room will often be impossible to quantify, and may not be apparent from the grand jury transcript. As one court wrote:
“A change in expression, a pressure on the hand or a warning glance would not be shown upon the minutes but might well influence, suppress or alter testimony to the prejudice of the defendant. There may have been prior expressions or conversations between the two witnesses which the one then giving testimony might well hesitate to repudiate or modify in the presence of the other. The District Attorney here contends . . . that defendant suffered no prejudice by the joint presence of the two sisters, but . . . ‘[t]he court cannot know that this suggestion represents the fact.’ We think the practice offers too great a possibility for the exercise of undue influence to be condoned.” State v. Revere, 232 La. 184, 207, 94 So. 2d 25, 34 (1957) (emphasis omitted; citations omitted; internal quotations omitted).
Any case-by-case analysis to determine whether the defendant was actually prejudiced is simply too speculative to afford defendants meaningful protection, and imposes a difficult burden on the courts that outweighs the benefits to be derived. The distinction between the truly harmless error and the more dangerous one is not “such a pronounced one that the Court can cloak the one with the mantle of legality and *87yet recognize the dangers of the other and prohibit it.” United States v. Carper, 116 F. Supp. 817, 821 (DC 1953).
That approach, finally, is likely to require a detailed inquiry that will frustrate and undermine the secrecy of grand jury inquiry. See United States v. Treadway, 445 F. Supp. 959 (ND Tex. 1978). The district court may have to discuss the testimony of grand jury witnesses who did not appear at trial. The goals of grand jury secrecy, however, counsel that such analysis should not be spread across the public record. See United States v. Sells Engineering, Inc., 463 U. S. 418, 424-425 (1983).4
IV
This litigation illustrates the extent to which the Court is willing to reduce the substantive law to “pretend-rules,” Borello, 766 F. 2d, at 58, in order to affirm a criminal conviction. But by denigrating Congress’ commands and eviscerating enforcement of Rule 6(d), the Court creates “a greater danger to a free people than the escape of some criminals from punishment.” United States v. Di Re, 332 U. S. 581, 595 (1948). I believe that the District Court in this case *88should have reversed defendants’ conspiracy convictions without inquiry into the prejudice done to defendants by the Rule 6(d) violation. I therefore would affirm the judgment of the Court of Appeals.
Denial of a Rule 6(d) motion could conceivably be subject to interlocutory appeal under the collateral-order doctrine of Cohen v. Beneficial Industrial Loan Corp., 337 U. S. 641 (1949). Such an order may be both collateral to the main action and, as a result of today’s opinion, wholly unreviewable after final judgment. Cf. United States v. Hollywood Motor Car Co., 458 U. S. 263, 267 (1982) (claim that indictment should be dismissed on grounds of prosecutorial vindictiveness not subject to interlocutory appeal because reviewable after conviction); United States v. Garner, 632 F. 2d 758 (CA9 1980) (claim that indictment should be dismissed on grounds of grand jury irregularities not subject to interlocutory appeal be*82cause reviewable after conviction); United States v. Bird, 709 F. 2d 388, 391, and n. 17 (CA5 1983) (collecting cases).
Our case law, further, is inconsistent with the majority’s broad holding that any error in the grand jury proceedings, no matter how egregious, is rendered harmless beyond a reasonable doubt by a petit jury’s subsequent guilty verdict. Vasquez v. Hillery, 474 U. S. 254 (1986), involving the “grave constitutional trespass” of racial discrimination, id., at 262, belies that holding. The Court’s assessment of the nature of the grand jury process refutes the rationale articulated by the majority today:
“Nor are we persuaded that discrimination in the grand jury has no effect on the fairness of the criminal trials that result from that grand jury’s actions. The grand jury does not determine only that probable cause exists to believe that a defendant committed a crime, or that it does not. In the hands of the grand jury lies the power to charge a greater offense or a lesser offense; numerous counts or a single count; and perhaps most significant of all, a capital offense or a noncapital offense — all on the basis of the same facts. Moreover, ‘[t]he grand jury is not bound to indict in every case where a conviction can be obtained.’ United States v. Ciambrone, 601 F. 2d 616, 629 (CA2 1979) (Friendly, J., dissenting). Thus, even if a grand jury’s determination of probable cause is confirmed in hindsight by a conviction on the indicted offense, that confirmation in no way suggests *85that the discrimination did not impermissibly infect the framing of the indictment and, consequently, the nature or very existence of the proceedings to come.” Vasquez v. Hillery, supra, at 263 (emphasis added).
See also 2 W. LaFave & J. Israel, Criminal Procedure § 15.6, p. 332 (1984) (“Most federal courts . . . treat unauthorized presence as a per se ground for dismissal, requiring no showing of prejudice”). Cases cited by the Solicitor General as requiring harmless-error analysis are distinguishable. Those cases involved only brief, inadvertent interruptions of the grand jury, during which the grand jury proceedings came to an immediate halt, United States v. Computer Sciences Corp., 689 F. 2d 1181, 1185-1186 (CA4 1982), cert. denied, 459 U. S. 1105 (1983); United States v. Kahan & Lessin Co., 695 F. 2d 1122, 1124 (CA9 1982); United States v. Rath, 406 F. 2d 757 (CA6), cert. denied, 394 U. S. 920 (1969), or a “fleeting” appearance in the grand jury room by a person assisting in the movement of bulky documents, United States v. Condo, 741 F. 2d 238, 239 (CA9 1984), cert. denied, 469 U. S. 1164 (1985). Indeed, the Fourth Circuit panel, whose reasoning was adopted by the en bane court, saw no inconsistency between Computer Sciences, supra, and the per se rule of the instant case. 735 F. 2d 136, 139-140 (1984).
Justice O’Connor suggests, noting the reference to 18 U. S. C. §556 (1946 ed.) in the Advisory Committee Notes to Rule 6, that the rulemakers intended violations of Rule 6(d) to be subject to the harmless-error rule. Ante, at 75-76. The legislative history of former § 556 does not support that view. The section, as first enacted in 1872, provided that “[n]o indictment . . . shall be deemed insufficient, nor shall the trial, judgment, or other proceeding thereon be affected by reason of any defect or imperfection in matter of form only, which shall not tend to the prejudice of the defendant.” Rev. Stat. § 1025 (emphasis added). There is no indication that this law was meant to disturb the settled law regarding unauthorized persons in the grand jury room, see United States v. Edgerton, 80 F. 374 (Mont. 1897); rather, it seems likely that the statute was directed at technical defects in the wording of the indictment, see, e. g., People v. St. Clair, 56 Cal. 406 (1880) (reversing conviction because word “larceny” in indictment was misspelled); People v. Vice, 21 Cal. 344 (1864) (reversing conviction because indictment, while alleging that defendant took certain property by threats and force, failed to allege that the property did not belong to defendant). See also supra, at 82.