BAZELON, Chief Judge:
This appeal requires us to resolve a sharp conflict between the power of a grand jury to extract testimony from a recalcitrant witness, and the power of a witness to withhold testimony on the basis of her fourth and fifth amendment rights. The interests on both sides are clearly substantial. While the protections afforded by the fourth and fifth amendments have been acknowledged and nourished by numerous decisions, it is no less clear that the grand jury’s effectiveness as a vehicle for investigating crime can be significantly impaired by unwarranted judicial interference. Indeed, one indication of Congress’s desire to avoid such unnecessary impairment is the statutory provision which permits us no more than thirty days to resolve appeals of this sort.1 The precise question presented is one of first impression before [1241] this Court. Within the past several months, however, the right of a witness to withhold testimony has been considered by a number of other circuits.2 Here, as in the analogous cases, appellants sought shelter under the fourth and fifth amendments as well as the wiretap provisions of the 1968 Omnibus Crime Control Act3 in steadfastly refusing to answer any of the grand jury’s questions. The District Court rejected appellants’ constitutional and statutory arguments and held both of them in contempt. Even in view of the unquestioned interest in efficiency of grand jury proceedings, we find merit in appellants’ contentions and therefore reverse the District Court’s judgment.
I.
Appellants Carol Evans and Marlene Fishlowitz 4 were each subpoenaed to appear before a federal grand jury sitting in the District of Columbia. At her first appearance on June 8, Miss Evans refused to testify, insisting that the grand jury’s questions were the fruit of an unlawful wiretap. On June 15 Miss Evans was ordered to testify by Chief Judge Sirica of the District Court, but on her return to the grand jury she persisted in refusing to answer the following questions : (1) Have you now or ever had any connection with the People’s Coalition for Peace and Justice? (2) What is the May Day Collective and have you ever been a member of that collective, or had any connection with the Collective? (3) Have you ever traveled for, or on behalf of, the People’s Coalition for Peace and Justice? (4) Have you ever attended any meetings of members of the May Day Collective in which the May Action Activities were discussed? Because of her assertion of the fifth amendment privilege against self-incrimination, Miss Evans was granted immunity under 18 U.S.C. § 2514 (1970) on June 22. Upon her continued refusal to answer the government’s questions she was found in civil contempt, 28 U.S.C. § 1826 (1970), by Chief Judge Sirica. Appellant filed an immediate notice of appeal with this Court, and we ordered her released pending the appeal.5
The facts with regard to Marlene Fishlowitz are similar. On June 15 she made a motion before Judge Parker of the District Court for disclosure of the government’s alleged electronic surveillance against her and to quash the grand jury’s subpoena. Judge Parker initially granted her motion, but on June 17 directed that his own order be vacated in view of Rule 77(K) (3) of the District Court which provides that the Chief Judge shall “ * * * determine all matters relating to proceedings before the grand jury.” On June 29 Chief Judge Sirica denied Miss Fishlowitz’s motion, and she appeared before the grand jury on that date. On the basis of several objections, including arguments under the fourth and fifth amendments, Miss Fishlowitz refused to answer any questions. She was granted immunity under § 2514 on the morning of June 30, but continued to resist answering the following questions: (1) Have you ever been a member of the May Day Collective or the People’s Coalition for Peace and Justice? (2) Have you ever traveled for or on behalf of the People’s Coalition for Peace and Justice or the May Day Collective? (3) Do you know Rene Davis or John Froines? (4) Have you ever [1242] attended any meetings or gatherings with Rene Davis or John Froines where the activities of May 3,1971, were discussed ? On that same day Chief Judge Sirica declared appellant in civil contempt under 28 U.S.C. § 1826. Like Miss Evans, she was released pending appeal pursuant to our order.6
II.
In defending their refusal to answer the grand jury’s questions, both appellants submitted affidavits stating their belief that wiretapping and electronic surveillance had been directed against them and that the grand jury’s subpoenas and questions were the fruit of that wiretap. If appellants had presented these assertions in the context of a criminal trial in which they were defendants, there would be no dispute over the procedure to be followed. Under 18 U.S.C. § 2518(10) (a) 7 appellants would be permitted to move for the suppression of evidence derived from an unlawful interception of wire or oral communications. The motion to suppress would provide appellants with a remedy to protect the right embodied in 18 U.S.C. § 2515,8 which flatly prohibits the introduction of evidence derived from an unlawful wiretap in any trial, hearing, or similar proceeding. And on the basis of appellant’s mere assertion that an unlawful interception had been conducted, the government would be required to affirm or deny the occurrence of the alleged wiretap. 18 U.S.C. § 3504.9 Still, the government insists that none of these procedures are available to these appellants because they were not defendants in a criminal prosecution, but merely witnesses before a grand jury.10 Furthermore, since they have both been granted immunity from prosecution they are not even potential defendants. The question, therefore, is whether the Omnibus Crime Control Act of 1968 should be interpreted in such a manner that the protections it provides to those who are victimized by unlawful electronic searches would not be available to a “mere witness.” While a number of circuits have purported to decide the question, the en banc decision of the Third Circuit in In re Egan11 is directly in point,12 and it [1243] offers the only sensitive and penetrating analysis of the statute. While I cannot accept all of the assertions in the two opinions which announced the judgment of the court,13 I am persuaded by much of the court’s reasoning.
The premise on which our interpretation of the statute must be based is a proper understanding of the statute’s purposes. In enacting the wiretap provisions of the Omnibus Crime Control Act, Congress plainly recognized the dangers inherent in the interception of wire and oral communications. The language of the statute as well as the statement of Congressional findings and legislative history are replete with indications of Congress’s concern with these dangers.14 The Act’s essential purpose, in our opinion, was to combine a limited and carefully articulated grant of power to intercept communications with an elaborate ’set of safeguards to deter abuse and to expunge its effects in the event that it should occur. It is thus important to "keep in mind not only the powers that Congress was willing to grant, but also those that it refused to make available despite the needs of law enforcement. Moreover, since the Act’s prohibitions and limitations were designed, in our view, as a precondition to the acceptability of any wiretapping at all, we must enforce them zealously or else throw Congress’s entire conception into jeopardy.
There are two provisions of the Act which could be interpreted so as to provide the relief appellants seek. Faced with a comparable choice, a majority of the Third Circuit read § 2515 to permit a witness to withhold testimony where questions propounded by the grand jury were tainted by an unlawful wiretap. By relying on the flat prohibition of § 2515, the majority could avoid decision on the interpretation of § 2518(10) (a). Only two judges expressed the view that a motion to suppress tainted evidence under § 2518(10) (a) could be made by a witness in a grand jury proceeding. While I am sympathetic to the majority’s effort to base the decision on the narrowest possible ground, and while I am inclined to accept the majority’s interpretation of § 2515, I believe that § 2518(10) (a) offers a stronger ground for decision.
In his concurring opinion in Egan, Judge Rosenn builds a substantial case in favor of the interpretation of § 2515 urged by appellants Evans and Fishlowitz. I see no need to reiterate here the steps in his analysis. I should comment, however, on two difficulties that he did not consider.
First, § 2515 describes in the most sweeping possible terms a prohibition against the use of. evidence tainted by an unlawful wiretap. But the section gives no indication of a specific remedy by which this prohibition is to be enforced. Viewed as a whole, however, the Omnibus Crime Control Act does provide such a remedy — the motion to suppress authorized by § 2518(10) (a). Moreover, the committee report which accompanied the Act explicitly indicated the committee’s expectation that § 2518(10) (a) would be read as the remedy for, and [1244] hence limitation on, the “right” created by § 2515.15 Because it is our function to interpret statutes, not committee reports, the committee’s language is not conclusive on the question. I tend to place greatest reliance on the language that was formally enacted into legislation, and on its face § 2515 does seem unequivocal in its application. Still, the committee report does no more here than restate the conventional maxim that a statute should be considered as a whole, and for that reason it may be entitled to greater weight. To avoid deciding precisely how much weight the committee’s language should be accorded, I would prefer to rest our decision on § 2518(10) (a).
The second source of my unease with Judge Rosenn’s treatment of § 2515 is related to the first. For just as § 2515 provides no apparent remedy for the right it creates, it also gives no clear indication of the parties in whose favor the right may be invoked. At a minimum, to be sure, the party invoking the section’s prohibition must be an “aggrieved person” as defined in § 2510 (ll).16 But that definition does not resolve the underlying problem. If § 2515 is capable of standing on its own without reference to § 2518(10) (a), then it is unclear who has standing to move for the exclusion of tainted evidence. It could be argued, of course, that an aggrieved person whose communications have been intercepted should be permitted to intervene in any proceeding where he believes that evidence from the interception is being used, even if he would not otherwise be a participant in any capacity in that proceeding. That approach, despite its obvious shortcomings, is at least consistent with the view that § 2515 has independent force. It is not, however, the approach adopted by Judge Rosenn. Instead, he would draw a distinction between cases where the aggrieved person is already before the court (for example, as a witness), and cases where he is not (for example, where the government introduces the evidence by calling as a witness the agent who carried out the unlawful interception).17 While that approach might obviate some of the practical difficulties that would arise if any person who thought his telephone had been tapped could intervene, I am not persuaded that the distinction has any relevance to § 2515. If the purpose of that section is, in fact, to preclude the introduction of any evidence tainted by an unlawful wiretap, then it is unclear to me why anything should turn on whether or not the aggrieved person is already before the court or grand jury. Because our decision is grounded on § 2518(10) (a), we do not need to open up this difficult issue of standing.
These difficulties in Judge Rosenn’s approach are by no means insurmountable, and if no other ground were avail[1245] able I expect that I would resolve my doubts in favor of his position. But since I do not share his apparent uncertainty about the application of § 2518(10) (a) to appellants,18 I do not find it necessary to decide whether § 2515 carries its own remedy. My conclusion that appellants have standing to move for the suppression of evidence under § 2518(10) (a) minimizes, in my opinion, the difficulty with the legislative history, and makes possible a more coherent interpretation of the statute as a whole.
On its face, § 2518(10) (a) would seem to permit a witness before a grand jury to invoke the prohibition of § 2515. It can be argued, however, that the intent of Congress — as indicated by the Senate committee report which accompanied the Act19 — was to preclude precisely this type of motion to suppress. Indeed, we can see no other substantial argument against our interpretation of the section.20 Nevertheless, we believe that the argument based on the legislative history must fail for several reasons.
First, assuming that the committee report stood clearly for the proposition that grand jury witnesses should have no standing to move for the suppression of evidence, we would have difficulty accepting the report as, in effect, an amendment to the clear — and contrary —language of the statute. While reports are unquestionably entitled to weight in determining the purpose of a statute, they are neither enacted by Congress nor signed by the President, and thus they do not have the force of legislation 21
Second, whatever the deference an unambiguous committee report deserves, the report at issue here is decidedly unclear. As Judge Adams demonstrates persuasively in his opinion in Egan, the government’s interpretation of the committee report is inconsistent with the cases cited by the committee to illustrate its position. While a witness may not normally22 have a right to enforce limitations on the character of the evidence presented to a grand jury, witnesses have frequently been permitted to withhold testimony from a grand jury on the basis of a constitutional, statutory, or common law privilege.23 The com[1246] mittee report apparently intended to leave these precedents intact. What the report does suggest is that
one who has been illegally wiretapped but is not a witness called by the grand jury may not move to suppress; and that even a witness or defendant who objects to the use of illegal wiretaps in the proceedings may not move to quash the entire proceeding or even an indictment growing out of it.24
That interpretation of the statute flows naturally from the pertinent case-law.25
But even if the committee report were entitled to greater weight than we have suggested, and even if the report were unambiguous in its effort to overturn prior judicial decisions, we would still be unable to accept the government’s interpretation of § 2518(10) (a). If we were forced to the conclusion that the Omnibus Crime Control Act precluded any attack by a grand jury witness on the admissibility of evidence obtained in violation of the fourth amendment, the statute would present the gravest constitutional difficulties. Again, we are indebted to Judge Adams for his illuminating discussion of the constitutional background, and in particular the implications of Silverthorne Lumber Co. v. United States.26 Any effort to bar appellants Evans and Fishlowitz from objecting to evidence obtained in violation of the fourth amendment would seem to fly directly in the face of the holding and language of the Silverthorne opinion. In view of the Supreme Court’s recent affirmations of Silverthorne,27 we are unwilling to assume that the case has lost its validity or that Justice Holmes inadvertently unleashed a specious doctrine that can now be casually ignored.28 But in our opinion we need not explore at this point the precise ramifications of the Silverthorne doctrine. For it is beyond question that we should interpret statutes, wherever possible, so as to avoid significant constitutional difficulties.29 That principle requires us to interpret this statute to permit an attack by a witness on the admissibility of evidence seized in violation of the fourth amendment.
III.
Since a majority of this panel has concluded that the District Court’s summary rejection of appellants’ contentions was inconsistent with the protections accorded them by the Omnibus Crime Control Act, the judgment of contempt against both appellants must be vacated. That is not to say, however, that these appellants need never respond to the questions posed by the grand jury. But if the government wishes to pursue [1247] the examination of these witnesses, it must be prepared to follow the procedures prescribed by Congress for resolving disputes over the alleged use of unlawful wiretapping.
Section 3504(a) (1) of title 18 provides that when a party aggrieved by an unlawful wiretap moves for the suppression of evidence on the basis of the alleged interception, the opponent of the claim must affirm or deny the allegation. Since § 3504(a) (1) is triggered, in our view, by the mere assertion that unlawful wiretapping has been used against a party, the government must make the next move if it still wishes to interrogate these appellants. The government has shown laudable candor in previous cases in acknowledging interceptions when they have occurred, and we are therefore predisposed to accepting as conclusive the government’s answer. Thus, if the government now denies the existence of any wiretapping against appellants, they will presumably lose their statutory privilege to remain silent. Whether under some circumstances a witness should be permitted to traverse the government’s statement, or whether a witness should be able to shift the burden of going forward back to the government by making some showing to contradict the government’s assertion, are questions with great potential impact not only on the viability of the statutory and fourth amendment privilege, but also on the amount of disruption that will be imposed on grand jury proceedings. We leave these questions open for consideration in the first instance by the District Court.
The procedures mandated by Congress may impose burdens on federal investigative agencies — who will have to search their records for evidence of a wiretap if they wish to pursue the interrogation of these witnesses — and on the grand jury process. But it is not our function to impeach Congress’s finding that these burdens are justified by countervailing interests. Even if it were, we would have to conclude that the Congressional judgment was entirely consistent with a realistic appraisal of the problems actually involved.
At the outset, it is important to note that we are concerned here with no more than the marginal burden imposed by our ruling that the statutory privilege is available to witnesses as well as defendants. There is apparently no dispute that Congress intended to have these burdens imposed when a defendant or prospective defendant moves for the suppression of evidence under § 2518(10 (a). Still, it might be agued that the burdens are so substantial that Congress would not have extended the privilege to mere witnesses.
In a letter incorporated in the House report on the 1970 Organized Crime Control Act,30 the Justice Department described in detail the significant effort involved in determining whether a wiretap has been conducted in a particular case. But it is essential to recognize that the efforts described in that letter concerned interceptions conducted before passage of the 1968 Act. Since June 19, 1968, federal agencies have operated under stringent provisions requiring not only the reporting of individual wiretaps, but also the periodic compilation of lists which itemize all wiretaps lawfully undertaken.31 Even a hurried review of available records should reveal the existence of any wiretaps undertaken after June, 1968.
Evidence of pre-1968 electronic surveillance may, admittedly, be more elusive. But here too one must avoid a sim[1248] plistic approach that exaggerates the real burdens. In the 1970 Organized Crime Control Act Congress explicitly indicated that the usefulness of a particular interception is directly related to the amount of time which has intervened between the interception and the event about which information is sought. According to the Act, wiretaps conducted prior to June, 1968, are presumptively useless in investigating events that occur more than five years after the interception. Accordingly, a party is not permitted to object to the admission of evidence tainted by an unlawful wiretap if the wiretap was conducted more than five years before the event under investigation.32 Since the grand jury in this case was apparently investigating events that occurred in May, 1971, federal agencies will only have to determine whether a wiretap had been conducted against appellants Evans and Fishlowitz subsequent to May, 1966. Barely more than two years of pre-1968 wiretapping can possibly be relevant to this case. Since ¡pwe have virtually no information on the nature of the government’s record-keeping before 1968, we are reluctant to de- ¡ cide precisely how much effort the government must make to uncover evidence of pre-1968 wiretapping. In the case now ^before us, however, it seems highly doubtful that federal agents could have had these appellants under electronic surveillance — or even have known of their existence — more than three years ago. The question is thus unlikely to arise. Absent a record on the extent of the burden that would be imposed on the government, we reserve decision on the procedure to be followed if these appellants were to contend that wiretapping had been used against them before 1968.
Within several years the usefulness of all wiretaps conducted before 1968 will be entirely exhausted, and the government should be able to resolve these disputes by consulting a readily accessible list. The burden will remain great to be sure, if the government conducts wiretaps which are not properly reported and which are therefore unlawful. But it is hardly surprising that Congress did not strive for a procedure designed to save the government burdensome work when the work would not be burdensome but for the government’s violation of the 1968 Act.
It should also be clear that the burdens on the grand jury process will not be overwhelming. All witnesses are not hostile to the government’s position, and there is no reason to assume that our holding will vitiate the grand jury’s ability to gather information. In the present case, for example, the grand jurors heard testimony from a large number of witnesses who showed no hesitation in cooperating with the government. And even where a witness makes a bad faith allegation of wiretapping as a means of obstructing an investigation, the witness can still be compelled to answer as soon as the government demonstrates that no wiretaps were conducted, or that any wiretaps were lawful. Unless the government makes a habit of conducting lawless wiretaps, a motion under § 2518 (10) (a) can ordinarily be resolved with little difficulty.
The issue might arise more rarely, perhaps, if we required a witness to allege with great specificity exactly what facts underlie his belief that electronic surveillance took place. Thus, we might remand the case to require appellants to make a more elaborate showing if they wished to persevere in their refusal to testify. The short answer to that suggestion is that it contradicts the unambiguous procedure devised by Congress to resolve these eases. Congress directed that the government must affirm or deny the use of wiretapping as soon as an aggrieved party makes a [1249] “claim * * * that evidence is inadmissible because it is the primary product” of an unlawful wiretap.33 The rationale behind this procedure is apparent and persuasive. By hypothesis, electronic surveillance functions properly when its object has no idea that his communications are being intercepted. If we were to hold that a witness could make a “claim” only when he has found an electronic bug in his home, heard mysterious bleeps in his telephone, or rifled the files of the Justice Department, we would merely succeed in encouraging the government to improve its security as well as its technology.
Furthermore, Congress may well have recognized that a requirement of more specific pleading would exacerbate the very invasion of privacy which the procedures are designed to remedy. Where a witness alleges that private conversations have been intercepted, it would be a harsh rule that predicated his right to suppress the conversations on his disclosure of the name of the other party, much less the subject of their conversation. Short of revealing this type of information, it is hard to see how a witness could, in many cases, be more specific about the alleged wiretap.
Finally, it should be clear that there is far more at stake here than just the smooth functioning of grand jury investigations.34 The grand jury’s operation —and indeed our entire criminal process —could be streamlined if our laws and Constitution left room for draconian efforts to obtain evidence from defendants or witnesses. While perhaps less crude than some of the measures which might be employed, electronic surveillance nevertheless menaces the interests protected by the fourth amendment, and it is surely “the greatest leveler of human privacy ever known.” 35 Where it is carried on without legal sanction, Congress wisely concluded that any evidence it yields should not be admissible before a court or grand jury. That result may well be inefficient, but Congress considered it an indispensable prerequisite for insuring that law enforcment officials obey the law.
In his dissenting opinion, Judge Wilkey insists emphatically that our decision will impose an intolerable burden on the government. It is entirely possible, as he asserts, that the government’s task in “proving a negative” may in some situations be difficult. What he fails to recognize, however, is that the burden on a witness (or defendant) to come forward with more specific information would not merely be difficult — in most cases it would be utterly impossible. The government is handicapped, he argues, because they have too many records. Yet that is little comfort to the witness, who has none.
Judge Wilkey suggests that the answer to the problem may lie in computerization of the government’s wiretap records. Computers may or may not make these difficult problems disappear. That is not the question. In our effort to implement Congress’s plan for strict control of electronic surveillance, we specifically acknowledge that subsequent cases— which may bring to the surface new information about the relative burdens on the government and the moving party— may reveal that Congress misjudged the practical difficulties and that the statutory procedure cannot be carried out as Congress intended. We will have to meet that problem on a concrete record when, and if, it arises. We decide only that on the basis of the information now before us, it seems clear that Congress expected the government to answer appellants’ allegations of wiretapping if it wished to pursue the interrogation any further.
To be sure, appellants have merely asserted that wiretapping has been used against them. But this is not a case [1250] where a reasonable man would be startled to learn that electronic eavesdropping had, in fact, been used. On the contrary, in view of the government’s well publicized anxiety about the anti-war activities planned for May, 1971, it would almost be more surprising if some telephones had not been tapped. We do not mean to suggest that a witness can invoke the procedures of § 3504(a) (1) only when an allegation of wiretapping seems plausible on its face. But it is important to avoid misconceptions about the nature of appellants’ claim. Their allegations surely cannot be dismissed as patently frivolous; nor could we safely assert that they have been made in bad faith in order to obstruct the grand jury. The government, not appellants, has the information which can substantiate or dissolve their contentions, and for that reason Congress expected that the burden of going forward would shift to the government.
Given all the circumstances and the information now available to us, our decision is a cautious and narrow application of the procedures designed by Congress. It appears that Judge Wilkey takes an apocalyptic view of our decision because he differs with Congress fundamentally in his conception of what the problem is. He maintains, in effect, that the practice of government wiretapping has become so widespread — and the responsibility for controlling it so diffuse — that controls are no longer feasible. That, plainly, is precisely what alarmed Congress.36
IV.
In view of our holding that the contempt judgment must be reversed because the District Court withheld from appellants the procedural protections to which they were entitled under the Omnibus Crime Control Act, we need not consider appellants’ further argument that the purported grant of immunity under § 2514 was defective. Accordingly, we would not reach the question at this juncture except to note our difficulty with the District Court’s handling of the issue.
The legal standards which control the granting of immunity are well established. While immunity forestalls a criminal prosecution, it may nevertheless fail to hold the witness harmless from embarrassment, infamy, or reprisal. For this reason, and despite the obvious benefits a grant of immunity may offer, Congress has consistently expressed a strong policy against the use of “immunity baths.” 37 Thus, a grant of immunity can be effective only if the witness to whom it is extended is then under investigation for one of the crimes itemized in the pertinent immunity statute.38 With regard to the investigation of crimes not so itemized, Congress has specifically concluded that immunity should not be available as an investigative tool. The determination of whether or not a witness is being investigated for such a crime is essentially a question of fact which must be resolved on the basis of a number of factors. It is clear that the mere conclusory assertion by the government that the statute is being obeyed cannot conclude the inquiry. In general, the issue must be resolved by careful analysis of both the questions put to the witness prior to the application for immunity and the elements of the offense [1251] purportedly under investigation. The questions addressed to these appellants 39 are not necessarily inconsistent with an investigation into a possible violation of the anti-riot statute,40 the only type of investigation which could justify immunity in this case.41 But in announcing his conclusion that a riot offense investigation was underway, the District Court gave no indication that it had made the requisite inquiry into all of the circumstances. A cursory review of the questions posed to the witness or an uncritical acceptance of the government’s assertion would vitiate the Congressional limitations on the reach of the immunity statute. More is required of the District Court.
The judgment of the District Court is reversed and the case remanded for proceedings consistent with this opinion.
So ordered.