NEWMAN, Circuit Judge:
This criminal appeal concerns primarily the issue of whether a defendant is entitled to have immunity conferred upon defense witnesses who invoke their privilege against self-incrimination. The appeal is brought by Norman Turkish, who was convicted by a jury in the Southern District of. New York (Vincent L. Broderick, Judge) of evading income taxes and filing false income tax returns, 26 U.S.C. §§ 7201, 7206, and conspiring to defraud the United States, 18 U.S.C. § 371. The trial of Turkish and three co-defendants lasted 11 weeks. Turkish and one co-defendant were found guilty; only Turkish appeals.
The Government’s evidence established that Turkish was a principal participant in a scheme that used fraudulent means to enable C.R. Rittenberry & Associates, Inc., an oil company, to create artificial tax losses in one year, offset by equally artificial taxable gains in a subsequent year, thereby postponing for a year the taxes on millions of dollars of corporate income. The scheme involved the use of tax “straddles,” the simultaneous purchase and sale at different prices of equal numbers of commodity futures contracts to be performed in different months. In the normal use of tax straddles, opportunities for arguably lawful tax avoidance are created when the market price varies from the prices at which the original contracts were both bought and sold. If the market declines, the trader offsets his purchase with an equivalent sale, thereby locking in a tax loss on his original purchase. He then offsets his original sale contract with an equivalent purchase, thereby locking in an approximately equal profit on his original sale contract. He benefits when the profit is taxable in the year following realization of the loss. In normal transactions the trader takes the risk that market price movements will be too narrow to create much opportunity for tax postponement and also the more serious risk that prices will not move uniformly with respect to both his original contracts. In the latter event the profit available to be locked in may be less than the locked-in loss. Turkish and others avoided these risks by fraudulently manipulating virtually the entire business of one trading ring on the New York Cotton Exchange, the Crude Oil Futures Market. This enabled them to move prices up and down at will, so that Rittenberry could take short-term capital losses during one tax year and defer an equal amount of off-setting capital gain to a subsequent year, all with no risk and a considerable saving in the postponement of [771]*771taxes. Turkish not only orchestrated the fraudulent aspects of the scheme but also evaded taxes on the money he received as compensation for his role.
I.
The Indictment
Turkish contends that his conviction should be reversed because the conspiracy count of the indictment (Count One) did not charge an offense and was unconstitutionally vague. The conspiracy count alleged that Turkish and others conspired to “defraud the United States by impeding, impairing, obstructing and defeating the lawful functions of the Department of the Treasury in the collection of income taxes.” The crime of conspiring to defraud the United States, 18 U.S.C. § 371, includes acts that “interfere with or obstruct one of its lawful governmental functions by deceit, craft or trickery,” Hammerschmidt v. United States, 265 U.S. 182, 188, 44 S.Ct. 511, 512, 68 L.Ed. 968 (1924). The creation of artificial tax losses for a business by fraudulent manipulation of prices in a commodity market qualifies as such an act. Turkish contends that there would have been no crime had the oil company not taken the resulting losses as tax deductions. Even if the manipulation of prices was not, by itself, a federal offense, it became evidence of a federal offense when it was done; to avoid federal taxes. The Government alleged that Turkish’s activities on the Crude Oil Futures market were part of a conspiracy that involved other acts, not that these activities constituted the entirety of the crime.
The indictment is also sufficiently precise to meet the requirements of the Constitution and the Federal Rules of Criminal Procedure. Fed.R.Crim.P. 7(c) states, in part: “The indictment or the information shalkbe a plain, concise and definite written statement of the essential facts constituting the offense charged.” Count One specified Turkish’s alleged efforts to manipulate the Crude Oil Market in order to create tax losses for his co-defendant’s client. This was sufficient to inform him of the charges against him, and to enable him to prepare his plea and his defense accordingly. See Hamling v. United States, 418 U.S. 87, 117, 94 S.Ct. 2887, 2907, 41 L.Ed.2d 590 (1974).
II.
Defense Witness Immunity
The claim for defense witness immunity arose in the following circumstances. The Government presented its case by calling a number of witnesses involved in the fraudulent transactions, several of whom were co-conspirators. Of these, three had pleaded guilty to participation in the conspiracy and had received letter agreements that they would not be prosecuted for any other commodity market crimes or related tax offenses if they testified truthfully. Two other prosecution witnesses who had not been indicted received similar letters, one of which was sufficient to persuade its recipient to return from Switzerland for the trial. In addition, one prosecution witness was formally granted “use” immunity under 18 U.S.C. § 6002.
During the trial, and after the Government had concluded its case, Turkish and his co-defendants moved that seventeen of the prospective defense witnesses be granted “use” immunity and required to testify under 6002. They argued that these witnesses could provide exculpatory testimony, but would invoke their Fifth Amendment privilege and decline to testify unless compelled to do so. Judge Broderick invited the Government to consider granting “use” immunity to these witnesses pursuant to 6002. The Government did consider the matter, but decided not to grant immunity. Judge Broderick then reserved decision on defendants’ motion until after the trial, at which time the defendants moved for a new trial or acquittal. On August 23, 1979, Judge Broderick denied the defendants’ motion.
In a subsequent opinion, United States v. Turkish (S.D.N.Y.1979), Judge Broderick set forth his analysis of the issue and his reasons for denying the motion. Judge Bro-derick concluded that the Compulsory Proc[772]*772ess Clause of the Sixth Amendment does not give a defendant the right to require immunization of a witness, but that such a right is “probably” contained in the Due Process Clause of the Fifth Amendment. Id. However, he declined to accord the defendants the benefit of this “probable” Fifth Amendment right to defense witness immunity for two reasons. First, he ruled that the defendants’ motion was untimely, since it should properly have been made at the beginning of the trial. Second, he concluded that defense witness immunity would be available only to secure testimony that was material and exculpatory and that the defendants had not shown that any of the witnesses for whom they sought immunity would give material, exculpatory testimony.
To assess Turkish’s challenges to these rulings we deem it appropriate to explore the concept of defense witness immunity, a matter arising with increasing frequency before this and other courts. See, e. g., United States v. De Palma, 476 F.Supp. 775 (S.D.N.Y.1979), appeal pending sub nom. United States v. Horwitz, No. 79-1315 (2d Cir.); Government of the Virgin Islands v. Smith, 615 F.2d 964 (3d Cir. 1980).
Granting immunity to a defense witness at the defendant’s request seems to have been considered for the first time, in a reported decision, by Chief Justice Burger, then a Circuit Judge, as dictum in Earl v. United States, 361 F.2d 531, 534 n.l (D.C. Cir. 1966), cert. denied, 388 U.S. 921, 87 S.Ct. 2121, 18 L.Ed.2d 1370 (1967). Since then it has been much discussed by courts and commentators.1 Interest in defense witness immunity was considerably heightened after Congress enacted the “use” immunity statute, 18 U.S.C. §§ 6001-6005, in 1970, and the Supreme Court subsequently upheld its constitutionality, Kastigar v. United States, 406 U.S. 441, 92 S.Ct. 1653, 32 L.Ed.2d 212 (1972). No longer did an immunity grant forbid prosecution of the witness for crimes referred to in his testimony (“transactional” immunity). Now the Government could still prosecute the witness; it was barred only from making any use of his immunized testimony, either directly by putting the testimony in evidence at the witness’s trial, or indirectly by obtaining other evidence from leads that the testimony supplied.
Claims for defense witness use immunity have been uniformly rejected by this Court, United States v. Gleason, 616 F.2d 2 (2d Cir. 1979); United States v. Praetorius, 622 F.2d 1054 (2d Cir. 1979, modified on rehearing, May 7, 1980); United States v. Lang, 589 F.2d 92, 96 n.l (2d Cir. 1978); United States v. Wright, 588 F.2d 31, 33-37 (2d Cir. 1978), cert denied, 440 U.S. 917, 99 S.Ct. 1236, 59 L.Ed.2d 467 (1979); United States v. Stofsky, 527 F.2d 237, 249 (2d Cir. 1975), cert. denied, 429 U.S. 819, 97 S.Ct. 65, 50 L.Ed.2d 80 (1976); see also United States v. Housand, 550 F.2d 818, 823-824 (2d Cir.), cert. denied, 431 U.S. 970, 97 S.Ct. 2931, 53 L.Ed.2d 1066 (1977), and by almost all circuits to consider the matter, United States v. Lenz, 616 F.2d 960 (6th Cir. 1980); United States v. Smith, 542 F.2d 711, 715 (7th Cir. 1976); United States v. Alessio, 528 F.2d 1079, 1081-82 (9th Cir.), cert. denied, 426 U.S. 948, 96 S.Ct. 3167, 49 L.Ed.2d 1184 (1976); Thompson v. Garrison, 516 F.2d 986, 988 (4th Cir.), cert. denied, 423 U.S. 933, 96 S.Ct. 287, 46 L.Ed.2d 263 (1975); see Earl v. United States, 361 F.2d 531 (D.C. Cir. 1966), cert. denied, 388 U.S. 921, 87 S.Ct. 2121, 18 L.Ed.2d 1370 (1967) (transactional immunity). The claim is a matter of divided opinion in the Third Circuit, compare United States v. Rocco, 587 F.2d 144 (3d Cir. 1978); United States v. Berrigan, 482 F.2d 171 (3d [773]*773Cir. 1973), with Government of the Virgin Islands v. Smith, supra; United States v. Herman, 589 F.2d 1191, 1203-04 (3d Cir. 1978), cert. denied, 442 U.S. 913, 99 S.Ct. 2014, 60 L.Ed.2d 386 (1979); United States v. Morrison, 535 F.2d 223 (3d Cir. 1976). Additional support for the claim has been expressed by the former Chief Judge of the District of Columbia Circuit, see United States v. Gaither, 539 F.2d 753 (D.C. Cir.) (Bazelon, C. J., concurring in denial of rehearing en banc); cert. denied, 429 U.S. 961, 97 S.Ct. 388, 50 L.Ed.2d 329 (1976), United States v. Leonard, 494 F.2d 955, 985 n.79 (D.C. Cir. 1974) (Bazelon, C. J., concurring and dissenting), and by two District Courts, United States v. De Palma, supra, and United States v. La Duca, 447 F.Supp. 779 (D.N.J.1978), aff’d on other grounds sub nom. United States v. Rocco, supra, in addition to Judge Broderick in this case.
The only federal appellate decisions ruling in favor of defense witness immunity appear to be the Third Circuit decisions in Morrison and Smith. In Morrison a divided panel of the Third Circuit reversed a conviction on the ground that prosecutorial misconduct had caused a defense witness to withhold testimony out of fear of self-incrimination. As a remedy for the misconduct, the Court ordered that upon a retrial, the Government face the choice of either granting the witness use immunity or having the defendant acquitted.
Smith involved a totally bizarre situation. A juvenile defendant sought use immunity for a juvenile defense witness. The office of the Virgin Islands Attorney General, who had exclusive jurisdiction to prosecute both the defendant and the witness, was agreeable to use immunity for the witness. However, this local prosecuting office, as a matter of “prosecutorial courtesy,” 615 F.2d at 967, conditioned its approval upon the consent of the United States Attorney, who inexplicably declined to consent. In a thoughtful opinion Judge Garth reversed the conviction and remanded for determination of whether use immunity should have been conferred under standards explicated in the Court’s decision.
These standards rest on two different concepts. First, Judge Garth considered the power of a court to order the prosecutor to grant statutory use immunity pursuant to 18 U.S.C. § 6002. Such “statutory” immunity was held to be available for a defense witness with relevant testimony, 615 F.2d at 969 n.7, when the defendant could show that the prosecutor’s decision not to confer immunity was made “with the deliberate intention of distorting the judicial fact finding process,” id. at 966, a standard the Third Circuit had previously articulated in United States v. Herman, supra, 589 F.2d at 1204. Secondly, Judge Garth considered what he called “judicial” immunity, the power of a court, unaided by statute, to order that a witness’s testimony cannot be used against him. Again applying a standard earlier announced in United States v. Herman, supra, Judge Garth held that judicial immunity, i. e., court-ordered use immunity, was available for a witness “capable of providing clearly exculpatory evidence” when the Government can present no “strong countervailing interest.” 615 F.2d at 970.
Though Morrison and Smith stand in sharp contrast to the uniform holdings of other federal appellate decisions that have rejected defense witness immunity, some of these decisions have been careful to deny the claim only with respect to the precise facts presented, e. g., United States v. Wright, supra; United States v. Alessio, supra. Furthermore, two of our decisions have explicitly left open the possibility that defense witness immunity might be required if grants of use immunity to prosecution witnesses resulted in an “unfair advantage.” United States v. Gleason, supra, 616 F.2d at 28; United States v. Lang, supra, 589 F.2d at 96-97. In light of this state of the case law, further consideration of the constitutional bases for defense witness immunity is warranted. Resort is usually made to the Sixth and Fifth Amendments.
The established content of the Sixth Amendment does not support a claim for defense witness immunity. Traditionally, [774]*774the Sixth Amendment’s Compulsory Process Clause gives the defendant the right to bring his witness to court and have the witness’s non-privileged testimony heard, but does nor carry with it the additional right to displace a proper claim of privilege, including the privilege against self-incrimination. United States v. Lacouture, 495 F.2d 1237 (5th Cir.), cert. denied, 419 U.S. 1053, 95 S.Ct. 631, 42 L.Ed.2d 648 (1974); Myers v. Frye, 401 F.2d 18 (7th Cir. 1968); Johnson v. Johnson, 375 F.Supp. 872 (W.D. Mich.1974); Holloway v. Wolff, 351 F.Supp. 1033 (D.Neb.1972); see Royal v. Maryland, 529 F.2d 1280, 1283 (4th Cir. 1976) (Winter, J., dissenting). While the prosecutor may not prevent or discourage a defense witness from testifying, Washington v. Texas, 388 U.S. 14, 87 S.Ct. 1920, 18 L.Ed.2d 1019 (1967); United States v. Morrison, supra, it is difficult to see how the Sixth Amendment of its own force places upon either the prosecutor or the court any affirmative obligation to secure testimony from a defense witness by replacing the protection of the self-incrimination privilege with a grant of use immunity.
Arguably there is a more plausible basis for defense witness immunity in the more general and perhaps developing requirement of basic fairness protected by the Fifth Amendment’s Due Process Clause.2 The appeal to constitutionally protected fairness proceeds from two basic arguments. First, as this Circuit hinted in Gleason and Lang, unfairness may inhere in some situations because the Government’s grant of use immunity to its witnesses affords it an advantage over the defendant’s ability to present a defense. Secondly, to the extent that a trial is viewed as a search for the truth, denial of defense witness immunity may in some circumstances unfairly thwart that objective.3
The first contention, based on equalizing the powers of the prosecution and the defense, is entirely unpersuasive. A criminal prosecution, unlike a civil trial, is in no sense a symmetrical proceeding. The prosecution assumes substantial affirmative obligations and accepts numerous restrictions, neither of which are imposed on the defendant. The prosecution must prove the defendant’s guilt beyond a reasonable doubt to the satisfaction of all the jurors; it may not obtain the defendant’s testimony, suppress exculpatory evidence, nor retry the defendant after acquittal, even though errors prejudicial to the Government occurred. The defendant, by contrast, may prevail without offering any proof at all; he need not disclose whatever inculpatory evidence he discovers, may avoid conviction by persuading a single juror that reasonable doubt exists, and may challenge a conviction by direct appeal and subsequent collateral attack.
The system of criminal law administration involves not only this procedural imbalance in favor of the defendant, but also important aspects of the Government’s law enforcement power that are not available to the defendant. Subject to constitutional and statutory limits, the Government may arrest suspects, search private premises, wiretap telephones, and deploy the investigative resources of large public agencies. New would seriously argue that the public interest would be well served either by extending all of these powers to those accused of crime or by equalizing the procedural burdens and restrictions of prosecution and defendant at trial. Viewed in isolation, there is a surface appeal to the equal availability of use immunity for prosecution and defense witnesses. But in the context of criminal investigation and criminal trials, where accuser and accused have inherently different roles, with entirely different pow[775]*775ers and rights, equalization is not a sound principle on which to extend any particular procedural device. At a minimum, such a principle will not support a constitutional interpretation of Fifth Amendment fairness.
The second argument, based on the need to pursue the truth, has somewhat greater force. As a general rule the Government is properly obliged to divulge exculpatory evidence. Brady v. Maryland, 373 U.S. 83, 83 S.Ct. 1194, 10 L.Ed.2d 215 (1963). That principle, however, has heretofore been limited to evidence in the Government’s possession and has not been extended to create a Government obligation to assist the defense in extracting from others evidence the Government does not have. Moreover the concept of a trial as a search for the truth has always failed of full realization whenever important facts are shielded from disclosure because of a lawful privilege. The key fact needed to prove a defendant’s innocence may be contained in a client’s privileged admission to his attorney, or a husband’s privileged admission to his wife, as well as in the testimony of a witness protected by the privilege against self-incrimination. Nevertheless, it must be acknowledged that since the advent of immunity statutes, the self-incrimination privilege, unlike any other, can be displaced without any impairment of the legally protected rights of the holder of the privilege. And unlike transactional immunity, use immunity does not improve the legal position of the holder of the privilege; it leaves his legal rights precisely as they were before he testified. However, the grant of use immunity does implicate public interests, and any assessment of a claim for defense witness use immunity must reckon with those public concerns.
In the first place, while the prosecution remains theoretically free under Kastigar to prosecute a witness granted use immunity, the obstacles to a successful prosecution can be substantial. The Government has a “heavy burden” to prove that its evidence against the immunized witness has not been obtained as a result of his immunized testimony. Kastigar v. United States, supra, 406 U.S. at 461, 92 S.Ct. at 1665. While this burden can be met by cataloguing or “freezing” the evidence known to the Government prior to the immunized testimony, that technique is not available when continuing investigations disclose vital evidence after, though not resulting from, the immunized testimony. See SEC v. Stewart, 476 F.2d 755, 762 (2d Cir. 1973) (Timbers, J., dissenting). Moreover, to meet its burden of proving that prosecution of the immunized witness was not benefitted in any way by his immunized testimony the prosecutors most knowledgeable about an investigation may in some circumstances be obliged to forgo any further contact with the witness and arrange for a new team of investigators and prosecutors to pursue the case against him. See United States v. Kurzer, 534 F.2d 511 (2d Cir. 1976).
Secondly, awareness of the obstacles to successful prosecution of an immunized witness may force the prosecution to curtail its cross-examination of the witness in the case on trial to narrow the scope of the testimony that the witness will later claim tainted his subsequent prosecution. While the witness cannot prevent prosecution and secure an immunity “bath” by broadening the scope of his answers, as he could if testifying under a grant of transactional immunity, his fulsome answers may substantially lessen the likelihood of any successful prosecution.
Finally, there is considerable force to the Government’s apprehension that defense witness immunity could create opportunities for undermining the administration of justice by inviting cooperative perjury among law violators. Co-defendants could secure use immunity for each other, and each immunized witness could exonerate his co-defendant at a separate trial by falsely accepting sole responsibility for the crime, secure in the knowledge that his admission could not be used at his own trial for the substantive offense. The threat of a perjury conviction, with penalties frequently far below substantive offenses, could not be relied upon to prevent such tactics. More[776]*776over, this maneuver would substantially undermine the opportunity for joint trials, with consequent expense, delay, and burden upon disinterested witnesses and the judicial system.
How these substantial concerns are to be weighed against the defendant’s interest in securing truthful exculpatory testimony through defense witness immunity turns in large part upon whether the balancing of these interests is appropriately a judicial function. The Government suggests it is not, contending that the granting of immunity is pre-eminently a function of the Executive Branch. See Ullmann v. United States, 350 U.S. 422, 76 S.Ct. 497, 100 L.Ed. 511 (1956). On the other hand, the judiciary has constitutional responsibilities for the fairness of a trial. Moreover, as Judge Garth has argued in Smith, the court can accord use immunity without directly acting in the domain of either the Legislative or Executive Branch. A court can rule that testimony may not be used against a witness without adding any gloss to the use immunity statute or directing the prosecutor to use his statutory authority. Judicially created use immunity, albeit premised on constitutional considerations, was fashioned by the Supreme Court in Murphy v. Waterfront Commission of New York Harbor, 378 U.S. 52, 84 S.Ct. 1594, 12 L.Ed.2d 678 (1964) (witness’s compelled testimony barred from use by another jurisdiction), and in Simmons v. United States, 390 U.S. 377, 88 S.Ct. 967, 19 L.Ed.2d 1247 (1968) (defendant’s testimony at suppression hearing barred from use at trial). See also In re Grand Jury Investigation, 587 F.2d 589 (3d Cir. 1978) (testimony given to assert Speech and Debate Clause defense); United States v. Immon, 568 F.2d 326 (3d Cir. 1977) (testimony given to assert Double Jeopardy Clause defense).
However, a court cannot determine whether any constitutional provision requires a judicial grant of use immunity without assessing the implications upon the Executive Branch, both those that flow from a grant of use immunity and those that flow from an adjudication of whether such immunity might be appropriate in a particular case. The concerns previously expressed about the risk to other successful prosecutions are matters normally better assessed by prosecutors than by judges. Surely a court is in no position to weigh the public interest in the comparative worth of prosecuting a defendant or his witness, although if a court decides that immunity is required, it can always leave that ultimate assessment with the prosecutor by advising that trial of the defendant will continue only if the witness’s testimony is immunized. But confronting the prosecutor with a choice between terminating prosecution of the defendant or jeopardizing prosecution of the witness is not a task congenial to the judicial function.4
Still it may be contended, as Judge Garth did in Smith, that a court ought to determine in each case whether the risks to the public interest in conferring defense witness immunity outweigh the needs of the defendant. Smith suggests two types of inquiry: whether the prosecutor’s opposition to defense witness immunity stems from “the deliberate intention of distorting the fact finding process,” 615 F.2d 968, or whether the prosecutor can present “strong countervailing interest,” id. at 974, to the [777]*777defendant’s need for clearly exculpatory evidence. Either inquiry will propel a trial court into uncharted waters. Focusing upon the prosecutor’s intent will often lead to exploration and premature disclosure of the pending status of an investigation against the witness. Moreover, a prosecutor without enough evidence to seek indictment of a witness may legitimately prefer to maintain his option to prosecute on the basis of later information. It cannot fairly be argued, where the prosecutor declines to consent to use immunity, that the absence of present intention to prosecute is evidence of intention to distort the fact-finding process. Alternatively, weighing the “countervailing interest” in not granting defense witness immunity will in all likelihood prove to be as elusive a task as formulating any meaningful standards for the assessment. In the extraordinary fact situation presented by the Smith case, where the prosecutor opposing use immunity does not even have jurisdiction to prosecute the witness, the public interest in not granting defense witness immunity appears to be non-existent. But in most situations where defense witness immunity is likely to be sought, some legitimate opposing prosecution interest will exist, and constitutional fairness is not a satisfactory standard against which to assess such interests.
When any novel legal proposition is urged upon a court, there is a natural judicial reluctance to say “never.” Indeed, the extraordinary fact situation presented by the Smith case illustrates a situation where denial of defense witness immunity can be said to deny the defendant the fair trial guaranteed by the Due Process Clause. Yet it is important to recognize that Smith really does not involve a use of the Due Process Clause to balance the public interest in withholding immunity against the defense need for it. In Smith the prosecutor with jurisdiction over the witness was willing to grant use immunity. Opposition came from a prosecutor without jurisdiction. This was simply an instance of a prosecutor interfering, for no apparent reason, to suppress evidence that was about to become available to the accused. We have no dispute with the holding in Smith. However, in light of all the considerations previously discussed, we find ourselves in fundamental disagreement with the standards outlined in that decision. Without precluding the possibility of some circumstances not now anticipated, we simply do not find in the Due Process Clause a general requirement that defense witness immunity must be ordered whenever it seems fair to grant it. The essential fairness required by the Fifth Amendment guards the defendant against overreaching by the prosecutor, Giglio v. United States, 405 U.S. 150, 92 S.Ct. 763, 31 L.Ed.2d 104 (1972) (failure to disclose promise not to prosecute government witness); Waley v. Johnston, 316 U.S. 101, 62 S.Ct. 964, 86 L.Ed. 1302 (1942) (threat to use manufactured evidence); Taylor v. Lombard, 606 F.2d 371 (2d Cir. 1979) (knowing use of perjured testimony); United States v. Westbo, 576 F.2d 285 (10th Cir. 1978) (disobedience of court ruling excluding admission of other crimes evidence); cf. Santobello v. New York, 404 U.S. 257, 92 S.Ct. 495, 30 L.Ed.2d 427 (1971) (repudiation of plea bargain promise), and insulates him against prejudice. See, e. g., Ward v. Village of Monroeville, 409 U.S. 57, 93 S.Ct. 80, 34 L.Ed.2d 267 (1972) (judge had pecuniary interest in result); Sheppard v. Maxwell, 384 U.S. 333, 86 S.Ct. 1507, 16 L.Ed.2d 600 (1966) (trial subject to excessive publicity); Turner v. Louisiana, 379 U.S. 466, 85 S.Ct. 546, 13 L.Ed.2d 424 (1965) (prosecution witnesses present in jury room during deliberations); In re Murchison, 349 U.S. 133, 75 S.Ct. 623, 99 L.Ed. 942 (1955) (judge also served as one-person grand jury); Moore v. Dempsey, 261 U.S. 86, 43 S.Ct. 265, 67 L.Ed. 543 (1923) (trial occurred under threat of mob violence). It does not create general obligations for prosecutors or courts to obtain evidence protected by lawful privileges.
The circumstances of this case do not remotely approach a situation where lack of defense witness immunity could be found to deny constitutionally protected fairness. In the first place, the demand for immunity was initially made in the middle of the trial and properly found to be untimely by Judge Broderick for reasons set [?]*?out in the margin.5 See United States v. Taylor, 562 F.2d 1345, 1361 (2d Cir.), cert. denied, 432 U.S. 909, 97 S.Ct. 2958, 53 L.Ed.2d 1083 (1977); United States v. Jones, 487 F.2d 676, 679 (9th Cir. 1973); United States v. Grooms, 454 F.2d 1308, 1311 (7th Cir.), cert. denied, 409 U.S. 858, 93 S.Ct. 141, 34 L.Ed.2d 104 (1972). Secondly, Judge Broderick carefully considered the expected testimony of the witnesses sought to be immunized and concluded that none of them would provide material, exculpatory evidence. Their testimony would either have been cumulative, immaterial, or impeaching only on collateral matters. Thus, the trial court’s refusal to order the prosecutor to confer use immunity was plainly correct.
We have expressed our thoughts on the issue at some length because we do not agree with Judge Broderick’s views on the general availability of defense witness immunity, nor do we wish to see criminal trials regularly interrupted by wide-ranging inquiries concerning the specific pros and cons of defense witness immunity in a particular case. In fact, we think trial judges should summarily reject claims for defense witness immunity whenever the witness for whom immunity is sought is an actual or potential target of prosecution. No hearing should be held to establish such status. The prosecutor need only show that the witness has been indicted or present to the court in camera an ex parte affidavit setting forth the circumstances that support the prosecutor’s suspicion of the witness’s criminal activity. No duty is imposed upon the prosecutor; he simply has an option to rely upon the witness’s status as an actual or potential target of prosecution to foreclose any inquiry concerning immunity for that witness. If a case should arise where the witness is not an indicted defendant and the prosecutor cannot or prefers not to present any claim that the witness is a potential defendant, and if the defendant on trial demonstrates that the witness’s testimony will clearly be material, exculpatory, and not cumulative, it will be time enough to decide whether in those circumstances a [779]*779court has any proper role with respect to defense witness immunity. Of course, our limited interpretation of the Fifth Amendment’s application to this issue does not preclude broader action by United States Attorneys under the existing authority of § 6002 nor legislative action to define circumstances in which defense witness immunity should be granted.
Affirmed.