delivered the opinion of the Court.
The petitioner was brought to trial before a jury in the District of Columbia upon a charge of felony murder.1 At that trial the prosecution introduced three confessions allegedly made by the petitioner while he was in the custody of the police. After these confessions had been admitted in evidence, the petitioner took the witness stand and testified to his own version of the events leading to the victim’s death. The jury found the petitioner guilty, but the Court of Appeals reversed his conviction, holding that the petitioner’s confessions had been illegally obtained and were therefore inadmissible in evidence against him. Harrison v. United States, 123 U. S. App. D. C. 230, 238, 359 F. 2d 214, 222; on rehearing en banc, 123 U. S. App. D. C. 239, 359 F. 2d 223.2
*221The substance of the confessions was that the petitioner and two others, armed with a shotgun, had gone to the victim’s house intending to rob him, and that the victim had been killed while resisting their entry into his home. In his testimony at trial the petitioner said that he and his companions had gone to the victim’s home hoping to pawn the shotgun, and that the victim was accidentally killed while the petitioner was presenting the gun to him for inspection.
Upon remand, the case again came to trial before a jury. This time the prosecutor did not, of course, offer the alleged confessions in evidence. But he did read to the jury the petitioner’s testimony at the prior trial— testimony which placed the petitioner, shotgun in hand, at the scene of the killing. The testimony was read over the objection of defense counsel, who argued that the petitioner had been induced to testify at the former trial only because of the introduction against him of the inadmissible confessions. The petitioner was again convicted, and the Court of Appeals affirmed.3 We granted certiorari to decide whether the petitioner’s trial testimony was the inadmissible fruit of the illegally procured confessions.4
*222In this case we need not and do not question the general evidentiary rule that a defendant’s testimony at a former trial is admissible in evidence against him in later proceedings.5 A defendant who chooses to testify waives his privilege against compulsory self-incrimination with respect to the testimony he gives, and that waiver is no less effective or complete because the defendant may have been motivated to take the witness stand in the first place only by reason of the strength of the lawful evidence adduced against him.
Here, however, the petitioner testified only after the Government had illegally introduced into evidence three confessions, all wrongfully obtained,6 and the same principle that prohibits the use of confessions so procured also prohibits the use of any testimony impelled thereby — the fruit of the poisonous tree, to invoke a time-worn metaphor. For the “essence of a provision forbidding the acquisition of evidence in a certain way is that not merely evidence so acquired shall not be used before the Court but that it shall not be used at all.” Silverthorne Lumber Co. v. United States, 251 U. S. 385, 392.7
*223In concluding that the petitioner’s prior testimony could be used against him without regard to the confessions that had been introduced in evidence before he testified, the Court of Appeals relied on the fact that the petitioner had “made a conscious tactical decision to seek acquittal by taking the stand after [his] in-custody statements had been let in . ...”8 But that observation is beside the point. The question is not whether the petitioner made a knowing decision to testify, but why. If he did so in order to overcome the impact of confessions illegally obtained and hence improperly introduced, then his testimony was tainted by the same illegality that rendered the confessions themselves inadmissible.9 As Justice Tobriner wrote for the Supreme Court of California,
“If the improper use of [a] defendant’s extrajudicial confession impelled his testimonial admission of guilt, ... we could not, in order to shield *224the resulting conviction from reversal, separate what he told the jury on the witness stand from what he confessed to the police during interrogation.”10
The remaining question is whether the petitioner’s trial testimony was in fact impelled by the prosecution’s wrongful use of his illegally obtained confessions. It is, of course, difficult to unravel the many considerations that might have led the petitioner to take the witness stand at his former trial. But, having illegally placed his confessions before the jury, the Government can hardly demand a demonstration by the petitioner that he would not have testified as he did if his inadmissible confessions had not been used. “The springs of conduct are subtle and varied,” Mr. Justice Cardozo once observed. “One who meddles with them must not insist upon too nice a measure of proof that the spring which he released was effective to the exclusion of all *225others.” 11 Having “released the spring” by using the petitioner’s unlawfully obtained confessions against him, the Government must show that its illegal action did not induce his testimony.12
No such showing has been made here. In his opening statement to the jury, defense counsel announced that the petitioner would not testify in his own behalf. Only after his confessions had been admitted in evidence did he take the stand. It thus appears that, but for the use of his confessions, the petitioner might not have testified at all.13 But even if the petitioner would have decided to testify whether or not his confessions had been used, it does not follow that he would have admitted being at the scene of the crime and holding the gun when the fatal shot was fired. On the contrary, the more natural inference is that no testimonial admission so damaging would have been made if the prosecutor had not already *226spread the petitioner’s confessions before the jury.14 That is an inference the Government has not dispelled.
It has not been demonstrated, therefore, that the petitioner’s testimony was obtained “by means sufficiently distinguishable” from the underlying illegality “to be purged of the primary taint.” Wong Sun v. United States, 371 U. S. 471, 488. Accordingly, the judgment must be
Reversed.
An earlier conviction had been vacated on appeal. See n. 4, infra.
Two of the confessions were found to have been obtained in violation of Mallory v. United States, 354 U. S. 449. The third was found to have been obtained in violation of a prior en banc decision of the Court of Appeals, Marling v. United States, 111 U. S. App. D. C. 174, 295 F. 2d 161. See n. 6, infra.
128 U. S. App. D. C. 245, 387 F. 2d 203.
389 U. S. 969. The petitioner’s further contention that he was denied the right to a speedy trial is wholly without merit and was properly rejected by the Court of Appeals. See 128 U. S. App. D. C., at 248-250, 387 F. 2d, at 206-208. The petitioner was indicted more than eight years ago and has been tried and convicted three times for the offense here involved. His first conviction was vacated on appeal when it became clear that the man who had represented him in certain post-verdict proceedings was an ex-convict posing as an attorney, see 123 U. S. App. D. C. 230, 232-233, 359 F. 2d 214, 216-217; his second conviction was reversed because the Government employed inadmissible confessions against him on retrial, see 123 U. S. App. D. C. 230, 238, 239, 359 F. 2d 214, 222, 223; and his third conviction is presently before us. Virtually all of the delays of which the petitioner complains occurred in the *222course of appellate proceedings and resulted either from the actions of the petitioner or from the need to assure careful review of an unusually complex ease.
See, e. g., Edmonds v. United States, 106 U. S. App. D. C. 373, 377-378, 273 F. 2d 108, 112-113; Ayres v. United States, 193 F. 2d 739, 740-741. And see generally C. McCormick, Evidence §§ 131, 230-235, 239 (1954).
In the present posture of this case, the earlier holding of the Court of Appeals that the petitioner’s confessions were illegally obtained, see 123 U. S. App. D. C. 230, 238, 239, 359 F. 2d 214, 222, 223, is not in dispute. We therefore proceed upon the assumption that the Court of Appeals was correct in ruling the confessions inadmissible, but we intimate no view upon how we would evaluate that ruling if it were properly before us.
See also Nardone v. United States, 308 U. S. 338, 341; Wong Sun v. United States, 371 U. S. 471, 484-488. Cf. Fahy v. Connecticut, *223375 U. S. 85, 91. See also the opinions of Chief Justice Traynor in People v. Jackson, 67 Cal. 2d 96, 97, 429 P. 2d 600, 603, and People v. Polk, 63 Cal. 2d 443, 449, 406 P. 2d 641, 644, and the opinions of Justice Tobriner in People v. Spencer, 66 Cal. 2d 158, 164-169, 424 P. 2d 715, 719-724, and People v. Bilderbach, 62 Cal. 2d 757, 763-768, 401 P. 2d 921, 924-927.
128 U. S. App. D. C. 245, 252, 387 F. 2d 203, 210.
We have no occasion in this case to canvass the complex and varied problems that arise when the trial testimony of a witness other than the accused is challenged as “the evidentiary product of the poisoned tree.” R. Ruffin, Out on a Limb of the Poisonous Tree: The Tainted Witness, 15 U. C. L. A. Law Rev. 32, 44 (1967). See also Comment, Fruit of the Poisonous Tree — A Plea for Relevant Criteria, 115 U. Pa. L. Rev. 1136, 1143-1153 (1967). Compare United States v. Wade, 388 U. S. 218, 241; Gilbert v. California, 388 U. S. 263, 272-273. And, contrary to the suggestion made in a dissenting opinion today, post, at 234, we decide here only a case in which the prosecution illegally introduced the defendant’s confession in evidence against him at trial in its case-in-chief.
People v. Spencer, supra, 66 Cal. 2d, at 164, 424 P. 2d, at 719-720.
It is argued in dissent that the petitioner’s trial testimony should not be suppressed “even if it was in fact induced by the wrongful admission into evidence of an illegal confession,” post, at 232, since any deterrence such suppression might achieve is insufficient to warrant placing new “obstacles ... in the path of policeman, prosecutor, and trial judge alike.” Post, at 235. Of course, no empirical evidence on the deterrence issue is available. And “[s]ince as a practical matter it is never easy to prove a negative, it is hardly likely that conclusive factual data could ever be assembled.” Elkins v. United States, 364 U. S. 206, 218. But it is not deterrence alone that warrants the exclusion of evidence illegally obtained— it is “the imperative of judicial integrity.” Id., at 222. The exclusion of an illegally procured confession and of any testimony obtained in its wake deprives the Government of nothing to- which it has any lawful claim and creates no impediment to legitimate methods of investigating and prosecuting crime. On the contrary, the exclusion of evidence causally linked to the Government’s illegal activity no more than restores the situation that would have prevailed if the Government had itself obeyed the law.
De Cicco v. Schweizer, 221 N. Y. 431, 438, 117 N. E. 807, 810.
See People v. Spencer, supra, 66 Cal. 2d, at 168, 424 P. 2d, at 722. As Mr. Justice Harlan recently observed, “when the prosecution seeks to use a confession uttered after an earlier one not found to be voluntary, it has . . . the burden of proving . . . that the later confession . . . was not directly produced by the existence of the earlier confession.” Darwin v. Connecticut, 391 U. S. 346, 351 (concurring in part and dissenting in part). The same principle compels the conclusion that, when the prosecution seeks to use testimony given after the introduction in evidence of a confession unlawfully obtained, it has the burden of proving that the defendant's testimony was not produced by the illegal use of his confession at trial. Compare Chapman v. California, 386 U. S. 18, 24: "Certainly error ... in illegally admitting highly prejudicial evidence . . . casts on someone other than the person prejudiced by it a burden to show that it was harmless.”
“In evaluating the possibility that the erroneous introduction of [a] defendant’s extrajudicial confession might have induced his subsequent testimonial confession, we must assess [the] defendant’s reaction to the use of his confession at trial on the basis of the information then available to him . . . .” People v. Spencer, supra, 66 Cal. 2d, at 165, 424 P. 2d, at 720.
Compare United States v. Bayer, 331 U. S. 532: “Of course, after an accused has once let the cat out of the bag by confessing, no matter what the inducement, he is never thereafter free of the psychological and practical disadvantages of having confessed. He can never get the cat back in the bag. The secret is out for good. In such a sense, a later confession always may be looked upon as fruit of the first.” Id., at 540 (dictum). Compare also Darwin v. Connecticut, supra, 391 U. S. 346, 349; id., at 350-351 (separate opinion of Mr. Justice Harlan); Beecher v. Alabama, 389 U. S. 35, 36, n. 2; Clewis v. Texas, 386 U. S. 707, 710.