Mr. Justice Brennan
delivered the opinion of the Court.
This case presents important questions of construction and administration of the Jencks Act, 18 U. S. C. § 3500. That statute provides that in a federal criminal prosecution, after a witness called by the United States has testified on direct examination, the court, on motion of the defendant, shall order the United States to produce any “statement,” as defined in the Act, in the possession of the United States that relates to the subject matter as to which the witness has testified. The definition of “statement” in § 3500 (e) pertinent to this case is: “(1) a written statement made by said witness and signed or otherwise adopted or approved by him.”
At petitioner's trial in the District Court for the District of Arizona on charges of mail fraud in violation of 18 U. S. C. § 1341, the trial judge sustained the Government’s contention that certain writings of Government lawyers of conversations with the Government’s key witness were “the work product of counsel,” although the judge had not examined the writings. The Court of Appeals for the Ninth Circuit affirmed but on a different ground. In an unpublished memorandum opinion the Court of Appeals stated: “Apart from the question whether such notes were exempt from the Jencks Act. . . as ‘work product/ they were not statements of the [witness] within the meaning of § 3500 (e).” We granted certiorari limited to the Jencks Act question, 422 U. S. 1006.
We hold that a writing prepared by a Government lawyer relating to the subject matter of the testimony of a Government witness that has been “signed or otherwise adopted or approved” by the Government witness is producible under the Jencks Act, and is not rendered nonproducible because a Government lawyer interviews the witness and writes the “statement.” We hold further that in the circumstances of this case the Court of Appeals erred in determining in the first instance that the writings in question were not “statements.” We therefore vacate the judgment of the Court of Appeals and remand the case to the District Court for further proceedings consistent with this opinion, following the procedure in Campbell v. United States, 365 U. S. 85 (1961) (Campbell I).
I
Petitioner, with Edwin S. Newman and three other co-defendants, was charged in a multiple-count indictment with using the mails to defraud by means of a fraudulent scheme, which may be briefly summarized. The Financial Security Life Insurance Co., of which petitioner was president, issued single-premium annuities to various individuals; the policies purported to be fully prepaid and were used as collateral for loans. Promissory notes were accepted in lieu of the premiums, and interest on the notes was the only money paid to the company. Further, the policies were misrepresented as being free of liens or encumbrances. In fact, the policies were valueless. Petitioner concealed these facts from lenders who accepted the policies as collateral; indeed, the company refused payment of the proceeds of the policies to the lenders upon the ground of nonpayment of premiums. The three codefendants were charged with using the annuities as collateral to obtain loans. Petitioner used these “sales” of annuities to inflate the assets of the company on paper, intending eventually to sell the company.
Of the five defendants, only petitioner and Newman worked for the company. Newman agreed to plead guilty to a single count of the indictment and to testify as a Government witness. Thereupon his case was severed prior to petitioner’s trial. He was the key prosecution witness, revealing in great detail the operation of the fraudulent scheme and the transactions alleged in the indictment. Newman signed all of the correspondence with lenders, but testified that at all times he acted pursuant to instructions from petitioner. The Government’s case against petitioner consisted primarily of Newman’s testimony.
Prior to the trial, which covered seven weeks starting May 22, 1973, the Government delivered to petitioner a copy of Newman’s testimony before the grand jury, a memorandum of an interview with Newman conducted by a postal inspector over three years earlier, and a reporter’s transcript of an interview with Newman conducted by two Government lawyers on May 11, 1973. The May 11 transcript indicated that the lawyers intended to conduct further interviews with Newman concerning other transactions. At the trial, on cross-examination on June 27, Newman disclosed that he had met with the lawyers on May 13, June 9 and 10, and part of each day from June 16 through June 27. Unlike the May 11 meeting, no reporter was present. Newman’s forthcoming trial testimony was the subject of the discussion, but the notes of the interview were handwritten by the lawyers. Significantly, however, Newman testified, speaking of the May 13 interview:
“Q. And as they took notes, did they sometimes question you about what you had just said to make sure that they got it down correctly?
“A. They may have. I don’t really remember that that was part of the pattern.”
And again, speaking of the June 9 and June 10 interviews, Newman testified:
“Q. As you were explaining — or discussing your testimony, did anyone take notes?
“A. The two gentlemen took notes.
“Q. Were they occasionally read back to you to see whether or not they correctly understood what you were saying?
“A. Probably from time to time.
“Q. All right, sir. Did you either correct them or say, 'Yes, that’s right,’ or ‘No, that’s not right because it went this way, I believe,’ words to that effect?
“A. Yes, that would happen.”
Finally, he described this as the pattern followed at all remaining meetings with the lawyers.
At this point petitioner moved, pursuant to § 3500 (b), for an order directing the United States to deliver the notes to the defense. The trial judge, without waiting to hear from the Government, denied the motion on the ground that the material was “attorney’s work product.” Petitioner renewed the motion the following day, coupling the motion with a request that the Government be ordered to deliver the material for in camera inspection by the court. The motions were denied, but with leave to submit a memorandum in support of the motions. Petitioner’s memorandum argued against the existence of a “work product” exception and renewed the request for an order directing delivery of the material for in camera inspection. Thereafter, the Government orally argued that the material in question was not producible as “the work product of counsel,” and the judge again denied petitioner’s motions. On appeal, the material, which totaled 237 pages and was not part of the District Court record, was lodged with the Court of Appeals.
II
We see nothing in the Jencks Act or its legislative history that excepts from production otherwise producible statements on the ground that they constitute “work product” of Government lawyers. It is not clear from its brief that the Government argues to the contrary; rather, the Government's principal contention seems to be that in any event the principles underlying the “work product” doctrine suggest a narrow construction of “statement” as not to include a lawyer's “work product” even though it fits the statutory definition of a producible statement. We reject the argument, since the plain language of the statute, fully buttressed by legislative history, allows no room for the tendered exception.
The Government maintains that the Act can be read to include only statements given to a Government investigative or law enforcement agent during an investigation, and not those given to a Government trial attorney in preparation for trial. This contention rests in part on the original language of § 3500 (a), which postponed discovery, until after a witness’ direct examination, of statements of the witness made “to an agent of the Government.” But nothing in the Act even remotely suggests that "an agent of the Government” excludes Government lawyers. In any event, § 3500 (b) requires production of “any statement (as hereinafter defined) of the witness in the possession of the United States” without any limitation to statements made “to an agent of the Government.” Section 3500 (e)(1) defines a producible statement as one “made by said witness and signed or otherwise adopted or approved by him” with no limitation that it be a statement made “to an agent of the Government.”
The Government also suggests that Congress enacted the Jencks Act to limit the scope of this Court’s decision in Jencks v. United States, 353 U. S. 657 (1957), and since Jencks involved statements to an investigative agency — the Federal Bureau of Investigation — Congress intended to require production only of statements of witnesses made to investigative agencies, not those given to prosecutors in preparation for trial.
That the Act was not intended to limit the Jencks decision is apparent from its legislative history. Rather than limiting, the Act “reaffirms [Jencks] in its holding that a defendant on trial in a criminal prosecution is entitled to relevant and competent reports and statements in possession of the Government touching the events and activities as to which a Government witness has testified at the trial.” S. Rep. No. 981, 85th Cong., 1st Sess., 3 (1957). See H. R. Rep. No. 700, 85th Cong., 1st Sess., 4 (1957); Campbell I, 365 U. S., at 92. Moreover, Congress was concerned, not with the Jencks decision itself, but with “misinterpretations and misunderstandings” in application of Jencks in district courts and courts of appeals. S. Rep. No. 981, supra, at 3-5, 7-12; H. R. Rep. No. 700, supra, at 2-3, 6. The concern was that misapplication of Jencks would permit defendants “to rove at will through Government files.” S. Rep. No. 569, 85th Cong., 1st Sess., 3 (1957). See Palermo v. United States, 360 U. S. 343, 350 (1959). The House committee expressed its goal as that of preventing defendants from “rummag[ing] through confidential information containing matters of public interest, safety, welfare, and national security.” H. R. Rep. No. 700, supra, at 4. The objective of preventing “rummaging” plainly adds no support to the argument that Congress meant that distinctions should be made based upon the occupation of the Government official to whom the witness gave the statement.
The Government urges as a “primary reason” for adopting its construction that it is unfair to allow defense counsel to impeach a witness by using a statement that “could not fairly be said to be the witness’ own rather than the product of the investigator’s selections, interpretations and interpolations.” Palermo v. United States, supra, at 350. The short answer to that argument is that writings must be produced only to the extent they are “statements” as defined; further, §3500 (c) expressly provides a procedure for excising any matter not relevant to the witness’ direct testimony.
For the same reasons, we see no merit in the Government’s argument that, without an exception, disclosure of statements taken by Government lawyers may undermine the policies that gave rise to the work-product doctrine. See United States v. Nobles, 422 U. S. 225, 236-239 (1975); Hickman v. Taylor, 329 U. S. 495 (1947). Proper application of the Act will not compel disclosure of a Government lawyer’s recordation of mental impressions, personal beliefs, trial strategy, legal conclusions, or anything else that “could not fairly be said to be the witness’ own” statement. “If a government attorney has recorded only his own thoughts in his interview notes, the notes would seem both to come within the work product immunity and to fall without the statutory definition of a 'statement.’ ” Saunders v. United States, 114 U. S. App. D. C. 345, 349, 316 F. 2d 346, 350 (1963) (Reed, J.). Furthermore, if a witness has for some reason “adopted or approved” a writing containing trial strategy or similar matter, such matter would be excised under § 3500 (c) as not relating to the subject matter of the witness’ testimony or direct examination. Thus, the primary policy underlying the work-product doctrine — i. e., protection of the privacy of an attorney’s mental processes, United States v. Nobles, supra, at 238 — is adequately safeguarded by the Jencks Act itself.
The Government contends that production of statements written by Government lawyers “forces the attorney to testify as to what he remembers or what he saw fit to write down regarding witness’ remarks.” Hickman v. Taylor, supra, at 513. Although the risk of such testimony supported approbation of the work-product doctrine in Hickman, the nature of the disclosure provided by the Jencks Act differs significantly. In Hickman the Court concluded that there was no showing of necessity strong enough to justify the requested disclosure: there was a danger of inaccuracy and untrustworthiness, there was “[n]o legitimate purpose,” and use of the attorney’s words for impeachment would have made the attorney a witness rather than an officer of the court. 329 U. S., at 512-513. First, although there is some risk that a witness’ words will be distorted in notes taken by a Government lawyer, see Palermo v. United States, 360 U. S., at 352, there is no such danger where a witness has adopted or approved the lawyer’s notes. Second, there is a clearly legitimate — and congressionally recognized — purpose for disclosure under the Jencks Act. The Act requires disclosure of all statements for use in impeaching witnesses and “is thus designed to further the fair and just administration of criminal justice.” Campbell I, 365 U. S., at 92. Third, the lawyer is not called upon to be a witness, since statements are produced only where they can “fairly be said to be the witness’ own.” Finally, we cannot accept the Government’s claims that defense counsel will have a right to call Government lawyers as witnesses to “authenticate” their notes, nor do we find realistic the Government’s fear that a lawyer will “feel impelled” to take the stand.
We therefore conclude that the District Court erred in holding that the work-product doctrine bars production of writings otherwise producible under the Jencks Act.
Ill
The Court of Appeals erred in undertaking to make the initial determination whether the materials constituted producible “statements.” If that function may ever be properly undertaken by a court of appeals, the Court of Appeals should not have attempted to make the determination in this case. Campbell v. United States, 373 U. S. 487, 493 (1963) (Campbell II).
We have recognized that a Government objection to production may require that the trial court inspect documents or hold a hearing to gather extrinsic evidence bearing on the extent to which the documents are statements producible under § 3500. Campbell I, supra, at 92-93; Palermo v. United States, supra, at 354-355; cf. Campbell II, supra, at 493. In Campbell I the Court unanimously concluded that the trial judge was obliged to conduct some inquiry into the circumstances of the witness' interview there in question. 365 U. S., at 95; id., at 107-108 (Frankfurter, J., dissenting in part and concurring in result in part). The circumstances of this case compel the same conclusion. Newman's testimony raised a sufficient question under the Act to require the trial judge to conduct such an inquiry, and since we hold that the trial judge erred in exempting the material from production as attorneys' “work product,” a remand for such an inquiry by the District Court is required to determine whether petitioner’s motion should have been granted.
The necessity for a hearing in the District Court is highlighted by developments since our grant of the petition for certiorari. The Solicitor General has discovered that 40 of the 237 pages of material are not notes of Government lawyers but handwritten statements of Newman himself. Petitioner contends that the failure of the Government to turn over those 40 pages constitutes error requiring reversal of his conviction without more. The Government, although conceding that these 40 pages contain “statements,” argues that they nevertheless were not producible. The Government contends that Newman wrote the 40 pages after completing his direct testimony in order to aid the prosecution’s cross-examination of a defense witness, and thus are not producible because not in existence at the time of petitioner’s motion to produce, but the Government admits that these assertions are not based on facts in the record. Any inquiry regarding them is not for this Court but for the District Court on remand. The same is true of the claim that in any event the contents of the 40 pages deal largely, if not entirely, with matter other than Newman’s direct testimony.
As to the remainder of the 237 pages, there are other issues to be resolved on remand. For example, it will be necessary to determine whether the prosecutors’ notes were actually read back to Newman and whether he adopted or approved them. In addition, the court may have to consider whether the notes were in existence at the time of petitioner’s motion.
We of course intimate no view whether production of any of the 237 pages of material was required in this case. That determination is to be made by the District Court. We therefore conclude that the proper disposition of this case is that of Campbell I, supra, at 98-99. Petitioner is entitled to a redetermination of his motion for the production of the 237 pages of material. But we do not think that this Court should vacate his conviction and order a new trial, since petitioner’s rights can be fully protected by a remand to the trial court with direction to hold an inquiry consistent with this opinion. The District Court will supplement the record with findings and enter a new final judgment of conviction if the court concludes after the inquiry to reaffirm its denial of petitioner’s motion. This procedure will preserve petitioner’s opportunity to seek further appellate review on the augmented record. On the other hand, if the court concludes that the Government should have been required to deliver the material, or part of it, to petitioner, and that the error was not harmless, the District Court will vacate the judgment of conviction and accord petitioner a new trial.
The judgment of the Court of Appeals is therefore vacated, and the case is remanded to the District Court for further proceedings consistent with this opinion.
It is so ordered.
The statute provides in full:
“(a) In any criminal prosecution brought by the United States, no statement or report in the possession of the United States which was made by a Government witness or prospective Government witness (other than the defendant) shall be the subject of subpena, discovery, or inspection until said witness has testified on direct examination in the trial of the case.
“(b) After a witness called by the United States has testified on direct examination, the court shall, on motion of the defendant, order the United States to produce any statement (as hereinafter defined) of the witness in the possession of the United States which relates to the subject matter as to which the witness has testified. If the entire contents of any such statement relate to the subject matter of the testimony of the witness, the court shall order it to be delivered directly to the defendant for his examination and use.
“(c) If the United States claims that any statement ordered to be produced under this section contains matter which does not relate to the subject matter of the testimony of the witness, the court shall order the United States to deliver such statement for the inspection of the court in camera. Upon such delivery the court shall excise the portions of such statement which do not relate to the subject matter of the testimony of the witness. With such material excised, the court shall then direct delivery of such statement to the defendant for his use. If, pursuant to such procedure, any portion of such statement is withheld from the defendant and the defendant objects to such withholding, and the trial is continued to an adjudication of the guilt of the defendant, the entire text of such statement shall be preserved by the United States and, in the event the defendant appeals, shall be made available to the appellate court for the purpose of determining the correctness of the ruling of the trial judge. Whenever any statement is delivered to a defendant pursuant to this section, the court in its discretion, upon application of said defendant, may recess proceedings in the trial for such time as it may determine to be reasonably required for the examination of such statement by said defendant and his preparation for its use in the trial.
“(d) If the United States elects not to comply with an order of the court under subsection (b) or (c) hereof to deliver to the defendant any such statement, or such portion thereof as the court may direct, the court shall strike from the record the testimony of the witness, and the trial shall proceed unless the court in its discretion shall determine that the interests of justice require that a mistrial be declared.
“(e) The term ‘statement/ as used in subsections (b), (c), and (d) of this section in relation to any witness called by the United States, means—
“(1) a written statement made by said witness and signed or otherwise adopted or approved by him;
“(2) a stenographic, mechanical, electrical, or other recording, or a transcription thereof, which is a substantially verbatim recital of an oral statement made by said witness and recorded contemporaneously with the making of such oral statement; or
“(3) a statement, however taken or recorded, or a transcription thereof, if any, made by said witness to a grand jury.”
In the Court of Appeals’ opinion the bracketed word is “defendant” rather than “witness,” but this error was apparently inadvertent.
The Court granted the petition “limited to Question 8 presented by the petition,” 422 U. S. 1006, which reads as follows:
“Whether 18 U. S. C. § 3500, the Jencks Act, contains an ‘attorney’s work product exception’; and whether a Government attorney’s notes of conversations with the key Government witness, to whom the prosecutors read back their notes from time to time where the witness corrected same, which notes were prepared ‘only after lengthy conversations had occurred and a mutual understanding of the factual situation’ had been reached, if not compellable under the Jencks Act, are compellable under the doctrine of Brady vs. Maryland, [373 U. S. 83 (1963)].”
In light of our result, we need not address the Brady claim. See n. 15, infra.
The other three codefendants entered guilty pleas.
“We believe that there is no broad attorney’s work-product exception to the Jencks Act that shelters statements relating to the subject matter of the testimony of a witness merely because the statements were obtained by a government attorney rather than a government investigator. For if what is involved is truly the statement of the witness — that is, a statement written and signed or otherwise formally adopted or approved by him or a substantially verbatim recording of an oral statement — by definition it does not contain the mental impressions, trial strategy or personal beliefs of an attorney. Such material thus implicates only tangentially, if at all, the policies underpinning the work product doctrine.” Brief for United States 27-28. But an inconsistent position is suggested, id., at 19-20, 49-53, and n. 32.
The phrase “to an agent of the Government” was deleted from § 3500 (a) in 1970 when the Act was amended to add grand jury statements to the statutory definition of “statement.” Pub. L. 91-452, § 102, 84 Stat. 926. Petitioner recognizes that the deletion was not intended otherwise to expand the disclosure requirements of the Act.
The Government cites a statement by Senator Javits that “this bill is intended to relate only to statements or reports of government agents, and we understand those to mean enforcement officials,” 103 Cong. Rec. 15927 (1957), and argues that “[i]n common parlance a government trial attorney is not considered an ‘enforcement official.’ ” No justification is advanced, and we can think of none, for excluding some Department of Justice employees, but not others, from the category of enforcement officials. In any event the Javits statement is a weak reed upon which to rest the argument. Senator Javits’ statement had nothing whatever to do with the kind of official to whom a witness’ statement is given; he was responding to an inquiry as to the officials who must respond to an order to deliver materials:
“MR. WATKINS. Suppose the information is in the files of the United States marshal for the district.
“MR. JAVITS. The normal discovery rules would apply, because this bill is intended to relate only to statements or reports of Government agents, and we understand those to mean enforcement officials.” Ibid.
And that his use of the description “enforcement officials” was not meant as a limitation is crystal clear in his final response to the inquiry:
“MR. JAVITS. I am willing to say this to the Senator: I would be glad, for myself, to apply the provisions of this bill to all officials of the Federal Government. If the words do go that far,' it is perfectly all right with me, and I know exactly what I am voting for. I think they do.” Ibid.
The Government's assertion that Congress was concerned that “a government trial lawyer’s notes made in preparation for trial not be routinely disclosed to the defense” is totally without support in the legislative history and the Government cites none. On the contrary, the Government expressed its agreement with the disclosure of materials within the definition of § 3500 (e), without suggesting that a Government lawyer’s notes are protected. See H. R. Rep. No. 700, 85th Cong., 1st Sess., 7-12 (1957) (statement of Attorney General Brownell).
It is also urged that notes of an attorney of an interview will differ from those taken by investigative agents. The trial attorney, it is argued, is more likely to record mental impressions and trial strategy and take notes only for the purpose of personal recollection, a “highly individualistic matter.” The investigative agent, on the other hand, has assertedly greater concern with recording a witness’ statement completely, because he is gathering facts, “raw data,” to be used by others. Those arguments may be relevant to the determination whether given materials constitute a “statement,” but the distinction in this respect cannot, in the face of the Act’s broad and inclusive definition of “statement,” make the obligation to produce turn on the title of the official who takes the statement. In addition, the distinction would be recognized in proper administration of the Act. See injra, at 106.
Por the same reason, we are not persuaded that acceptance of a definition of “statement” that includes prosecutors' notes “might reveal the inner workings of the investigative process and thereby injure the national interest.” Palermo v. United States, 360 U. S. 343, 350 (1959).
There is no reason to require or permit such authentication where the district court has already determined that a writing has been adopted or approved by a Government witness.
The Government suggests that there may be a need for testimony to explain the meaning of a lawyer’s notes. But any explanation by the lawyer would be meaningless if the notes as written have been adopted or approved by the witness. Further, the Government asserts that a lawyer may want to testify to contradict his witness. Such a desire, we are told, is created where a witness repudiates some part of the notes that is inconsistent with the witness’ trial testimony. Once the court has found that the witness adopted or approved the lawyer’s writings, further testimony — either by the lawyer or the witness — as to whether the statement was made is repetitive and could be excluded by the court in its discretion. Fed. Rule Evid. 403. In addition, if the witness claims that he was being truthful in the statement and not at trial, or vice versa, or simply admits the inconsistency, we see no compelling motivation for testimony by the Government lawyer who wrote the statement; the statement used to impeach the witness is not the lawyer’s, but the witness’.
The Government also urges that the risk of forcing lawyers to testify would be eliminated by construing the Act to require written adoption or approval “comparable to a signature.” We see no realistic risk for the reasons stated above. Furthermore, we have not discovered any meaningful legislative history to support such a reading.
The Courts of Appeals that have considered the applicability of the “work product” doctrine to the Jencks Act have uniformly reached the same conclusion. Saunders v. United States, 114 U. S. App. D. C. 345, 349, 316 F. 2d 346, 350 (1963) (Reed, J.); United States v. Aviles, 315 F. 2d 186, 191 (CA2 1963); United States v. Hilbrich, 341 F. 2d 555, 557 (CA7), cert. denied, 381 U. S. 941 (1965); United States v. Smaldone, 484 F. 2d 311, 317 (CA10 1973), cert. denied, 415 U. S. 915 (1974).
Some courts have suggested that the trial court has an “affirmative duty” to secure the necessary evidence. E. g., Saunders v. United States, supra, at 348, 316 F. 2d, at 349; United States v. Chitwood, 457 F. 2d 676, 678 (CA6 1972); United States v. Keig, 320 F. 2d 634, 637 (CA7 1963); Ogden v. United States, 303 F. 2d 724, 734 (CA9 1962).
Pending the result of the proceedings on remand, we decline to examine the 237 pages of material. That is initially a task for the District Judge. For that reason, any disposition of the Brady issue raised by petitioner, see n. 3, supra, must be deferred pending the District Court’s inquiry on remand.
After this discovery the Solicitor General delivered all 237 pages of material to petitioner’s counsel. On oral argument he advised the Court that this disclosure was not intended as a concession that the material was producible under the Jencks Act.
The Government argues that the issues pertaining to the notes written by Newman are beyond the scope of our grant of certiorari, which was limited to the question whether there is an attorney’s work-product exception to the Jencks Act. See n. 3, supra. But petitioner was not aware at the time of filing his petition for review that 40 pages of the notes were written by Newman, and the petition obviously was intended to cover the full 237 pages of papers. In that circumstance we shall treat the questions raised by the Newman notes as subsumed in the question presented.
Another matter for the District Court is the parties’ dispute whether there was a proper Jencks request when Newman testified on rebuttal.
Every witness interview will, of course, involve conversation between the lawyer and the witness, and the lawyer will necessarily inquire of the witness to be certain that he has correctly understood what the witness has said. Such discussions of the general substance of what the witness has said do not constitute adoption or approval of the lawyer’s notes within §3500 (e)(1), which is satisfied only when the witness has “signed or otherwise adopted or approved” what the lawyer has written. This requirement clearly is not met when the lawyer does not read back, or the witness does not read, what the lawyer has written.
See n. 18, supra. By noting some of the issues that must be dealt with on remand — we hope we have set forth the most significant — we do not intend to limit the remand proceeding. It may be that further issues, heretofore overlooked or raised by evidence adduced in the remand proceeding, will also be presented for consideration.
Since courts cannot “speculate whether [Jencks material] could have been utilized effectively” at trial, Clancy v. United States, 365 U. S. 312, 316 (1961), the harmless-error doctrine must be strictly applied in Jencks Act cases. Campbell v. United States, 373 U. S. 487, 497 n. 14 (1963) (Campbell II); Rosenberg v. United States, 360 U. S. 367, 371 (1959); id., at 376 (Brennan, J., dissenting). See Kotteakos v. United States, 328 U. S. 750, 765 (1946); Gordon v. United States, 344 U. S. 414, 422-423 (1953).