concurring in the judgment.
In this case, we are asked to decide whether a witness who has testified before a federal grand jury pursuant to a grant of use immunity, 18 U. S. C. §§6001-6005, may be forced to testify about the same events in a subsequent civil deposition, despite his assertion of his Fifth Amendment privilege against self-incrimination. I agree with the Court’s conclusion that he may not be forced so to testify. Because I reach this conclusion only by a different route, I write separately to explain my views.
The statute authorizing grants of use immunity, 18 U. S. C. § 6002, provides that a witness may be ordered to testify despite his claim of a Fifth Amendment privilege, but “no testimony or other information compelled under the order (or any information directly or indirectly derived from such testimony or other information) may be used against the witness in any criminal case” (with stated limited exceptions). The Court notes that the parties in this case “make their arguments in terms tracking those of the statute— whether the deposition testimony is ‘derived from’ the prior testimony.” Ante, at 256. In the Court’s view, however, “the crux of their dispute is whether the earlier grant of immunity itself compelled Conboy to talk.” Ibid. It seems to me that by characterizing the issue in this way, the Court *273begs the question now before us. The earlier grant of immunity, by itself, obviously does not compel Conboy to testify at a later deposition. It is the District Court that has sought to compel Conboy’s testimony. Whether that court may do so is certainly the ultimate issue the Court must decide. But the Court’s rephrasing does not bring us closer to the answer.
It is, of course, black-letter law that a witness cannot assert a Fifth Amendment privilege not to testify “if the testimony sought cannot possibly be used as a basis for, or in aid of, a criminal prosecution against the witness.” Brown v. Walker, 161 U. S. 591, 597 (1896); see Mason v. United States, 244 U. S. 362, 365-366 (1917). In this case, however, the Court concludes that Conboy has a valid Fifth Amendment privilege “irrespective of whether ... his [deposition] answers could have been admitted against him at a criminal trial. ” Ante, at 257, n. 13. The Court never explains the basis for this conclusion, and it seems to me that it is plainly wrong. If Conboy’s deposition testimony cannot be used against him in a subsequent criminal prosecution, he cannot assert a Fifth Amendment privilege at his deposition and the District Court may compel him to testify. We must turn to § 6002 to determine whether the testimony can be so used. Section 6002 informs us that when immunity has been granted, the witness is protected against use of “information directly or indirectly derived from [the immunized] testimony.” Whether Conboy’s deposition testimony is so derived is the real issue before the Court.
The Court finds this statutory language irrelevant to its analysis. The Court asserts that petitioners have a “need for admissible evidence,” the Government has an “interest in limiting the scope of an immunity grant,” and respondent Conboy has an “interest. . . that [his Fifth Amendment] protection be certain.” Ante, at 258, 257. The Court then seeks to adjust these interests and arrive at a solution satisfactory to all. While this may be appropriate as a means of *274setting public policy,11 cannot agree that it is an appropriate method of statutory interpretation.
As with every case involving the construction of a statute, “our starting point must be the language employed by Congress.” Reiter v. Sonotone Corp., 442 U. S. 330, 337 (1979). If we were forced to examine the language of § 6002 without reference to its background and legislative history, the words of the statute might be sufficiently ambiguous so as to require resort to the policy concerns addressed by the Court. In this case, however, “regard for the specific history of the legislative process that culminated in the Act now before us affords more solid ground for giving it appropriate meaning.” United States v. Universal C. I. T. Credit Corp., 344 U. S. 218, 222 (1952).
II
A
This Nation’s first use immunity statute was passed by Congress in 1868. It provided that “no answer or other pleading of any party, and no discovery, or evidence obtained by means of any judicial proceeding from any party or witness . . . , shall be given in evidence, or in any manner used against such party or witness ... , in any court of the United States ... , in respect to any crime.” Act of Feb. 25, 1868, ch. 13, § 1, 15 Stat. 37. In Counselman v. Hitchcock, 142 U. S. 547 (1892), this Court held that immunity of this type could not be used to compel a witness to testify against himself, because it did not provide protection coextensive with the Fifth Amendment. The Counselman Court reasoned that the statute
*275“protected [the witness] against the use of his testimony against him ... in any criminal proceeding, in a court of the United States. But it had only that effect. It could not, and would not, prevent the use of his testimony to search out other testimony to be used in evidence against him .... It could not prevent the obtaining and the use of witnesses and evidence which should be attributable directly to the testimony he might give under compulsion, and on which he might be convicted, when otherwise, and if he had refused to answer, he could not possibly have been convicted.” Id., at 564.
In concluding, the Court stated that “no statute which leaves the party or witness subject to prosecution after he answers the criminating question put to him, can have the effect of supplanting the privilege conferred by the Constitution of the United States.” Id., at 585.
Due to this latter statement in the Counselman opinion, Congress and the lower courts assumed that only a broad “transaction” immunity would satisfy the requirements of the Fifth Amendment. Thus, beginning in 1893, Congress enacted a series of statutes giving a witness complete immunity from prosecution for any crime divulged in compelled testimony. This reliance on transaction immunity continued until 1970, when Congress enacted § 6002 as part of the Organized Crime Control Act of 1970, Pub. L. 91-452, 84 Stat. 927.
In the meantime, however, the Court decided several cases suggesting that some forms of use immunity would be constitutionally permissible. In Murphy v. Waterfront Comm’n, 378 U. S. 52 (1964), the Court held that a state witness could not be compelled to give testimony that could be incriminating under federal law “unless the compelled testimony and its fruits cannot be used in any manner by federal officials in connection with a criminal prosecution against him.” Id., at 79. In a footnote, the Court added that once a defendant had been immunized in a state proceeding, “the federal authori*276ties have the burden of showing that their evidence is not tainted by establishing that they had an independent, legitimate source for the disputed evidence.” Id., at 79, n. 18. Several years later, in Gardner v. Broderick, 392 U. S. 273, 276 (1968), the Court stated that “[a]nswers may be compelled regardless of the [Fifth Amendment] privilege if there is immunity from federal and state use of the compelled testimony or its fruits in connection with a criminal prosecution against the person testifying.” And shortly thereafter, in People v. La Bello, 24 N. Y. 2d 598, 602, 249 N. E. 2d 412, 414 (1969), the New York Court of Appeals interpreted Murphy and Gardner to hold that Counselman did not bar use immunity statutes, so long as they protected the immunized witness “from the use of his testimony or the fruits thereof.”
B
It was in this context that Congress in 1969 began considering a new type of immunity statute. The House and Senate Reports accompanying the Organized Crime Control Act of 1970 make clear that Congress was persuaded by the reasoning of these cases. After quoting from La Bello and discussing Counselman and Murphy at length, see S. Rep. No. 91-617, pp. 52-55 (1969); H. R. Rep. No. 91-1188, pp. 8-11 (1970), the Reports state that the statutory immunity provided by § 6002 “is intended to be as broad as, but no broader than, the privilege against self-incrimination. ... It is designed to reflect the use-restriction immunity concept of Murphy . . . rather [than] the transaction immunity concept of Counselman.” S. Rep. No. 91-617, at 145; H. R. Rep. No. 91-1188, at 12; see H. R. Rep. No. 91-1549, p. 42 (1970).
Section 6002’s prohibition against the use of compelled testimony or “any information directly or indirectly derived from such testimony” reflected Congress’ view of the extent of the Fifth Amendment privilege. According to the House and Senate Reports, the phrase was chosen to conform to “present law” on “the use of evidence derivatively obtained.” *277The Reports then cite Wong Sun v. United States, 371 U. S. 471 (1963), the seminal case on what is commonly known as the “fruits” doctrine, as representing “present law.” See S. Rep. No. 91-617, at 145; H. R. Rep. No. 91-1188, at 12; H. R. Rep. No. 91-1549, at 42. In Murphy and Gardner, upon which Congress relied, the Court had used the term “fruits” to describe the constitutional limits on use immunity. References to the “fruits” doctrine are scattered throughout the legislative history, whenever the boundaries of the use immunity statute are discussed.2 In Kastigar v. United States, 406 U. S. 441, 461 (1972), we recognized that the immunity § 6002 provides is “analogous to the Fifth Amendment requirement in cases of coerced confessions.” We noted that § 6002 was modeled on a recommendation from the National Commission on Reform of Federal Criminal Laws, and we quoted with approval a Commission report stating: “‘The proposed immunity is ... of the same scope as that frequently, even though unintentionally, conferred as the result of constitutional violations by law enforcement officers.’” Id., at 452, n. 36 (quoting Second Interim Report of the National Commission on Reform of Federal Criminal Laws, Mar. 17, 1969, Working Papers of the Commission 1446 (1970)).
In light of this evidence of legislative intent, the phrase “directly or indirectly derived from” in § 6002 cannot be re*278garded as ambiguous or lacking in meaning. It seems to me that Congress made its intent clear. First, it intended to grant only the minimum protection required by the Constitution. Second, it believed that the protection constitutionally required in cases of compelled testimony was identical to the protection required in cases of coerced statements or evidence otherwise illegally obtained.
Respondent Conboy’s interpretation of § 6002 is obviously narrower than that offered by petitioners; deposition testimony involving the same subject matter as prior immunized testimony would be protected by the prior grant of use immunity under petitioners’ interpretation, but not under Con-boy’s. Because Congress intended grants of use immunity to be as narrow as possible, we must accept Conboy’s interpretation if it is consistent with the Constitution. The question before us, then, is whether a witness’ Fifth Amendment rights would be violated if testimony given at a subsequent deposition were not covered by his grant of use immunity.
When an incriminating statement has been obtained through coercion, the Fifth Amendment prohibits use of the statement or its “fruits.” Congress understood this when it enacted § 6002, and, as the legislative history demonstrates, Congress intended to incorporate the “fruits” doctrine into the statute by use of the phrase “directly or indirectly derived.” In order to ascertain whether respondent Conboy’s deposition testimony would be “directly or indirectly derived” from his immunized grand jury testimony, and consequently whether Conboy’s interpretation of the statute is constitutional, we must determine whether the deposition testimony would be “fruits” as that concept is understood in the context of the Fourth and Fifth Amendments.3
*279HH HH HH
In Wong Sun v. United States, supra, the Court held that a statement following an illegal arrest must be suppressed as “fruits” of the arrest unless it results from “an intervening independent act of a free will,” and is “sufficiently an act of free will to purge the primary taint of the unlawful invasion.” 371 U. S., at 486. In Harrison v. United States, 392 U. S. 219, 222-224 (1968), the Court applied a similar standard to statements following an illegally obtained confession. Our more recent cases have adhered to this test. See, e. g., Rawlings v. Kentucky, 448 U. S. 98, 107-110 (1980); Brown v. Illinois, 422 U. S. 590, 600-604 (1975). In determining whether this standard is met, we examine a range of factors including the speaker’s knowledge of his Fifth Amendment rights; the temporal proximity of the constitutional violation and the subsequent statement; the nature of the violation and of the Government’s involvement; and, of course, the volun-tariness of the statement. See id., at 603-604. In brief, the issue is whether the speaker has voluntarily chosen to make the later statement, uninfluenced by the fact that prior statements have been compelled.4
I find little difficulty in concluding that if a witness in Conboy’s position were to testify during his civil deposition, his statements would not be “fruits” of his previous immunized testimony.5 In this case, Conboy attended his deposi*280tion accompanied by a lawyer. He was obviously aware of his Fifth Amendment rights, and he asserted them with vigor. There is no suggestion that Conboy was under a misapprehension about the relationship between his immunized testimony and his civil deposition. The deposition took place long after the conclusion of the immunized testimony, and Conboy did not remain under the impression that his testimony was being compelled by the Justice Department. From his past experience before the grand jury, Conboy knew that each time the Justice Department required his testimony, it provided a fresh grant of use immunity. Government attorneys were not involved in this civil case, and no fresh grant of immunity had been obtained. Under the circumstances, there was no danger that Conboy would inadvertently incriminate himself under some lingering compulsion of the prosecuting authorities. Any statement he made would have been an independent act of free will. Consequently, had Conboy answered the deposition questions, his testimony would not have been protected by the original immunity grant because it would not have been directly or indirectly derived from his immunized testimony.
In my view, a prior grant of use immunity could never justify compelling a witness’ testimony over a claim of Fifth Amendment privilege at a subsequent civil deposition. Although not every witness will be as well informed as Conboy, any witness who asserts the privilege necessarily engages in an independent act of free will. The assertion of the privilege should signal the judge supervising the civil proceedings that the testimony may well not be “derived from” the immunity grant.6 Although the compelled testimony would be in*281admissible at a subsequent criminal trial,71 agree with the Court that a witness should not be forced to rely upon the uncertainties of a later motion to suppress. This would indeed “ ‘ “let the cat out” with no assurance whatever of putting it back.’” Ante, at 262 (quoting Maness v. Meyers, 419 U. S. 449, 463 (1975)).
I do not mean to suggest, however, that whenever a witness immunized in prior proceedings testifies at a civil deposition without asserting a Fifth Amendment privilege, his testimony automatically should be admissible against him in a subsequent criminal prosecution. If there is a subsequent prosecution and the Government seeks to introduce deposition testimony of this sort, the judge in the criminal case should determine whether, under the circumstances, the deposition testimony is inadmissible as “derived from” the prior immunized statements. If the witness reasonably believed that his.prior grant of immunity protected his testimony, the testimony might well be derived from the immunity grant under the standards I have set forth above. If, on the other hand, the deposition testimony was a truly independent act of free will, it would be admissible in any later prosecution.
As Justice Stevens’ dissent demonstrates, the interests of the Government and the parties are not at all as clear as the Court asserts. Reliance on these interests is particularly inappropriate in a case such as this one, where the Government is not a party and we can only speculate about which interpretation of the statute would best serve the Government’s interest in law enforcement.
See, e. g., S. Rep. No. 91-617, p. 108 (1969) (§6002 “is a restriction against use of incriminating disclosures or their fruits”); Hearings on S. 30 et al. before the Subcommittee on Criminal Laws and Procedures of the Senate Committee on the Judiciary, 91st Cong., 1st Sess., 216 (1969) (report of New York County Lawyers’ Association) (under § 6002, the “testimony so compelled or its fruits may not be used against the witness”); id., at 281 (statement of Rep. Poff) (rule of § 6002 is “similar to the exclusionary rule which is now applied to evidence assembled in violation of various constitutional rights”); id., at 506 (statement of Sen. McClellan) (use immunity statutes can be made constitutional “through the use of the fruit of the poisonous tree process of derivative suppression, an analogy borrowed from fourth amendment illegally obtained evidence cases”).
The considerations underlying the Fifth Amendment “fruits” doctrine are not necessarily the same as those relevant in the Fourth Amendment context. With respect to the issue before us, however, Fourth Amendment “fruits” cases provide us with (guidance in determining whether a wit*279ness’ deposition testimony is “derived from” prior immunized testimony within the meaning of § 6002.
In Kastigar v. United States, 406 U. S. 441, 459 (1972), we recognized that Congress intended § 6002 to provide the minimum protection required by the Constitution. Wong Sun and its progeny establish that the “fruits” doctrine provides all the protection the Constitution requires. Thus, although my analysis is framed in terms of constitutional standards, the issue here of what the Constitution requires is not different from the issue of what Congress intended.
My analysis is necessarily limited to the choices facing a witness prior to the threat of contempt by the district court. The witness cannot be held in contempt unless the testimony sought is protected by the grant of *280use immunity or, in other words, unless it would be “fruits.” The question whether the testimony would be “fruits” thus cannot turn on whether the district court has issued a contempt order.
1 agree with Justice Stevens that the existence of a witness' Fifth Amendment privilege does not depend on his decision to assert the privilege. See post, at 287, n. 7. Nevertheless, the state of mind of the *281witness is relevant to a “fruits” inquiry, because a witness’ statements are “fruits” only if they do not result from an independent act of free will. Cf. Harrison v. United States, 392 U. S. 219, 222-224 (1968). A witness’ assertion of the privilege is strong evidence of that state of mind; the witness has demonstrated that he feels free to decide whether or not to speak.
It seems to me beyond question that deposition testimony compelled by means of a contempt order, over the assertion of a Fifth Amendment privilege, would be inadmissible at a subsequent criminal trial whether or not it was later held to be within the scope of the original grant of immunity. If the testimony was within the grant of immunity (i. e., if it was “fruits”), it would be inadmissible under § 6002. If the testimony was not within the grant of immunity, the witness should have been permitted to assert his privilege and the testimony wrongfully compelled should be excluded. See Maness v. Meyers, 419 U. S. 449, 474 (1975) (White, J., concurring in result).