opinion: Mr. Justice Stewart
  delivered the opinion of the Court.
  The petitioners were convicted by a jury in the District Court for the Southern District of New York of conspiring to import and conceal heroin in violation of the federal narcotics laws. An important part of the Government’s evidence consisted of tape recordings of conversations among several of the petitioners in a New York City hotel room. The tapes were made by federal officers in the adjoining room by means of an electronic recording device which did not physically intrude into the petitioners’ room. Because there was no “trespass” or “actual intrusion into a constitutionally protected area,” the District Court and the Court of Appeals rejected the petitioners’ argument that this evidence was inadmissible because the eavesdropping had violated their rights under the Fourth Amendment. The convictions were affirmed, and we granted certiorari to consider the constitutional questions thus presented.
  Last Term in Katz v. United States, 389 U. S. 347, we held that the reach of the Fourth Amendment “cannot turn upon the presence or absence of a physical intrusion into any given enclosure.” Id., at 363. Noting that the “Fourth Amendment protects people, not places,” id., at 351, we overruled cases holding that a search and seizure of speech requires some trespass or actual penetration of a particular enclosure. We concluded that since every electronic eavesdropping upon private conversations is a search or seizure, it can comply with constitutional standards only when authorized by a neutral magistrate upon a showing of probable cause and under precise limitations and appropriate safeguards. The eavesdropping in this case was not carried out pursuant to such a warrant, and the convictions must therefore be reversed if Katz is to be applied to electronic surveillance conducted before the date of that decision. We have concluded, however, that to the extent Katz departed from previous holdings of this Court, it should be given wholly prospective application. Accordingly, and because we find no merit in any of the petitioners’ other challenges to their convictions, we affirm the judgment before us.
  We are met at the outset with the petitioners’ contention that Katz does not actually present a choice between prospective or retroactive application of new constitutional doctrine. The Court in that decision, it is said, did not depart from any existing interpretation of the Constitution, but merely confirmed the previous demise of obsolete decisions enunciating the distinction between “trespassory” searches and those in which there was no physical penetration of the protected premises. Goldman v. United States, 316 U. S. 129; Olmstead v. United States, 277 U. S. 438. But this contention misconstrues our opinion in Katz. Our holding there that Goldman and Olmstead “can no longer be regarded as controlling,” 389 U. S., at 353, recognized that those decisions had not been overruled until that day. True, the principles they expressed had been modified. The belief that an oral conversation could not be the object of a “search” or “seizure” had not survived. And in Silverman v. United States, 365 U. S. 505, we had cautioned that the scope of the Fourth Amendment could not be ascertained by resort to the “ancient niceties of tort or real property law.” 365 U. S., at 511. But the assumption persisted that electronic surveillance did not offend the Constitution unless there was an “actual intrusion into a constitutionally protected area.” While decisions before Katz may have reflected growing dissatisfaction with the traditional tests of the constitutional validity of electronic surveillance, the Court consistently reiterated those tests and declined invitations to abandon them. However clearly our holding in Katz may have been foreshadowed, it was a clear break with the past, and we are thus compelled to decide whether its application should be limited to the future.
  Ever since Linkletter v. Walker, 381 U. S. 618, 629, established that “the Constitution neither prohibits nor requires retrospective effect” for decisions expounding new constitutional rules affecting criminal trials, the Court has viewed the retroactivity or nonretroactivity of such decisions as a function of three considerations. As we most recently summarized them in Stovall v. Denno, 388 U. S. 293, 297,
  “The criteria guiding resolution of the question implicate (a) the purpose to be served by the new standards, (b) the extent of the reliance by law enforcement authorities on the old standards, and (c) the effect on the administration of justice of a retroactive application of the new standards.”
  Foremost among these factors is the purpose to be served by the new constitutional rule. This criterion strongly supports prospectivity for a decision amplifying the evidentiary exclusionary rule. Thus, it was principally the Court’s assessment of the purpose of Mapp v. Ohio, 367 U. S. 643, which led it in Linkletter to deny those finally convicted the benefit of Mapp’s extension of the exclusionary rule to the States:
  “all of the cases . . . requiring the exclusion of illegal evidence have been based on the necessity for an effective deterrent to illegal police action. . . . We cannot say that this purpose would be advanced by making the rule retrospective. The misconduct of the police . . . has already occurred and will not be corrected by releasing the prisoners involved.” 381 U. S., at 636-637.
  We further observed that, in contrast with decisions which had been accorded retroactive effect, “there is no likelihood of unreliability or coercion present in a search- and-seizure case”; the exclusionary rule is but a “procedural weapon that has no bearing on guilt,” and “the fairness of the trial is not under attack.” 381 U. S., at 638, 639. Following this reasoning of Linkletter, we recently held in Fuller v. Alaska, 393 U. S. 80, that the exclusionary rule of Lee v. Florida, 392 U. S. 378, should be accorded only prospective application. Analogizing Lee to Mapp, we concluded that evidence seized in violation of § 605 of the Federal Communications Act was “no less relevant and reliable than that seized in violation of the Fourth Amendment,” and that both decisions were merely “designed to enforce the federal law.” 393 U. S., at 81.
  The second and third factors — reliance of law enforcement officials, and the burden on the administration of justice that would flow from a retroactive application— also militate in favor of applying Katz prospectively. Katz for the first time explicitly overruled the “physical penetration” and “trespass”, tests enunciated in earlier decisions of this Court. Our periodic restatements of those tests confirmed the interpretation that police and courts alike had placed on the controlling precedents and fully justified reliance on their continuing validity. Nor had other courts theretofore held that the prohibitions of the Fourth Amendment encompassed “non-trespassory” electronic surveillance. On the contrary, only a few months before the eavesdropping in this case, the Court of Appeals for the Second Circuit had upheld the introduction of electronic evidence obtained by the same narcotics agent with a virtually identical installation. United States v. Pardo-Bolland, 348 F. 2d 316, cert. denied, 382 U. S. 944.
  Although there apparently have not been many federal convictions based on evidence gathered by warrantless electronic surveillance, we have no cause to doubt that the number of state convictions obtained in reliance on pre-Katz decisions is substantial. Moreover, the determination of whether a particular instance of eavesdropping led to the introduction of tainted evidence at trial would in most cases be a difficult and time-consuming task, which, particularly when attempted long after the event, would impose a weighty burden on any court. Cf. Alderman v. United States, ante, at 180-185. It is to be noted also that we have relied heavily on the factors of the extent of reliance and consequent burden on the administration of justice only when the purpose of the rule in question did not clearly favor either retroactivity or prospectivity. Because the deterrent purpose of Katz overwhelmingly supports nonretroactivity, we would reach that result even if relatively few convictions would be set aside by its retroactive application.
  The petitioners argue that even if Katz is not given fully retrospective effect, at least it should govern those cases which, like the petitioners’, were pending on direct review when Katz was decided. Petitioners point out that in Linkletter, the only other case involving the retroactivity of a Fourth Amendment decision, the Court held Mapp applicable to every case still pending on direct review on the date of that decision. A similar approach was adopted in Tehan v. Shott, 382 U. S. 406, with respect to the prospectivity of Griffin v. California, 380 U. S. 609. In Johnson v. New Jersey, 384 U. S. 719, however, we abandoned the approach taken in Linkletter and Tehan and concluded that “there are no jurisprudential or constitutional obstacles” to the adoption of a different cut-off point. Id,., at 733. We explained that Here, on the other hand, as in Johnson, “the possibility of applying [Katz] only prospectively is yet an open issue.” Ibid.
  “[o]ur holdings in Linkletter and Tehan were necessarily limited to convictions which had become final by the time Mapp and Griffin were rendered. Decisions prior to Linkletter and Tehan had already established without discussion that Mapp and Griffin applied to cases still on direct appeal at the time they were announced.” Id., at 732.
  All of the reasons for making Katz retroactive also undercut any distinction between final convictions and those still pending on review. Both the deterrent purpose of the exclusionary rule and the reliance of law enforcement officers focus upon the time of the search, not any subsequent point in the prosecution, as the relevant date. Exclusion of electronic eavesdropping evidence seized before Katz would increase the burden on the administration of justice, would overturn convictions based on fair reliance upon pre-Katz decisions, and would not serve to deter similar searches and seizures in the future.
  Nor can it sensibly be maintained that the Court is foreclosed by Linkletter in this case, as it was not in Johnson, simply because Katz, like Mapp, was a Fourth Amendment decision. In neither Linkletter nor Johnson was it intimated that the cut-off points there adopted depended in any degree on the constitutional provision involved. There is, moreover, a significant distinction between the Mapp and Katz decisions. Mapp dealt solely with the applicability of the exclusionary rule to the States; “the situation before Mapp . . . [was that] the States at least knew that they were constitutionally forbidden from engaging in unreasonable searches and seizures under Wolf v. Colorado, 338 U. S. 25 (1949).” Before Katz on the other hand, “non-trespassory” electronic surveillance was not thought to fall within the reach of the Fourth Amendment. Therefore, this case lacks whatever impetus the knowingly unconstitutional conduct by the States may have provided in Linkletter to apply Mapp to all pending prosecutions.
  In sum, we hold that Katz is to be applied only to cases in which the prosecution seeks to introduce the fruits of electronic surveillance conducted after December 18, 1967. Since the eavesdropping in this case occurred before that date and was consistent with pre-Katz decisions of this Court, the convictions must be
  Affirmed.
  Mr. Justice Black, while adhering to his dissent in Linkletter v. Walker, 381 U. S. 618, 640 (1965), concurs in the affirmance of the judgment of convictions in this case for the reasons stated in his dissenting opinion in Katz v. United States, 389 U. S. 347, 364 (1967).
  Mr. Justice Marshall took no part in the consideration or decision of this case.
  35 Stat. 614, as amended, 21 U. S. C. § 173 provides in pertinent part:
  “It is unlawful to import or bring any narcotic drug into the United States or any territory under its control or jurisdiction . . . .” 21 U. S. C. § 174 provides in pertinent part:
  “Whoever fraudulently or knowingly imports or brings any narcotic drug into the United States or any territory under its control or jurisdiction, contrary to law, or receives, conceals, buys, sells, or in any manner facilitates the transportation, concealment, or sale of any such narcotic drug after being imported or brought in, knowing the same to have been imported or brought into the United States contrary to law, or conspires to commit any of such acts in violation of the laws of the United States, shall be imprisoned not less than five or more than twenty years and, in addition, may be fined not more than $20,000.”
  The room occupied by the petitioners was separated from that of the agents by two doors with a small air space between them. According to the testimony of the federal agents — which was properly credited by both courts below after an exhaustive hearing that included an actual reconstruction of the equipment in the hotel room — the microphone was taped to the door on their side. The face of the microphone was turned toward the %-inch space between the door and the sill, and a towel was placed over the microphone and along the bottom of the door in order to minimize interference from sounds in the agents’ room. A cable was run from the microphone to an amplifier and tape recorder in the bathroom adjoining the agents’ room.
  Petitioners contend that this installation was equivalent to a physical penetration of the petitioners’ room because the airspace between the doors acted as a sound chamber, thereby facilitating the pickup of the conversations next door. We are unable, however, to distinguish this eavesdropping from that condoned in Goldman v. United States, 316 U. S. 129, where the agents simply placed a sensitive receiver against the partition wall. Petitioners’ reliance on Silverman v. United States, 365 U. S. 505, is misplaced. The heating duct system used as a sound conductor by the agents in that case was “an integral part of the premises occupied by the petitioners,” 365 U. S., at 511, and the agents had to penetrate the petitioners’ house with a “spike microphone” before the heating duct could be thus employed.
  384 F. 2d 889.
  390 U. S. 943.
  The only other issues which warrant mention relate to the Government’s disclosure to the Court of Appeals of two instances of admittedly trespassory electronic surveillance affecting the petitioners. The Court of Appeals remanded the case to the District Court for a full evidentiary hearing on the subject matter of the disclosures. The first monitoring episode occurred during 1962-1963, when a device was installed in a Florida restaurant. The surveillance was directed at the owner of the restaurant rather than at any of the petitioners, but petitioner Dioguardi was overheard talking about the operations of the restaurant. The log sheets covering the entire period of surveillance were turned over to the District Judge for in camera inspection, and those relating to any conversations of Dioguardi were furnished to the defense. The second instance was an attempted bugging of a rented car used by petitioners Nebbia, Desist, and LeFranc in furtherance of the conspiracy. Again all records pertaining to this episode were turned over to the defense.
  District Judge Palmieri, after holding an extensive hearing at which the petitioners were granted unrestrained opportunity to introduce evidence and cross-examine witnesses, concluded that none of the “evidence used against [the petitioners] at the trial was tainted by any invasion of their constitutional rights.” 277 F. Supp. 690, 700. Judge Palmieri found that the Dioguardi conversations overheard in 1962-1963 were totally unrelated to the events of the conspiracy, which transpired over two years later. With regard to the second instance, he found that the device in-installed in the rented car “did not function and that nothing coherent was obtained.” Id., at 692. The Court of Appeals held that these findings were supported by the evidence and that the petitioners were accorded all the procedural rights to which they were entitled. We agree. See Alderman v. United States, ante, p. 165.
  See also On Lee v. United States, 343 U. S. 747.
  See also 389 U. S., at 362 (Harlan, J., concurring); 389 U. S., at 367, 372 (Black, J., dissenting).
  See, e. g., Wong Sun v. United States, 371 U. S. 471, 485; Lanza v. New York, 370 U. S. 139, 142; Silverman, v. United States, 365 U. S. 505; Irvine v. California, 347 U. S. 128.
  Silverman v. United States, supra, at 512.
  In Katz, 389 U. S., at 353, for example, we referred to our previous observation in Warden v. Hayden, 387 U. S. 294, 304, that “[t]he premise that property interests control the right of the Government to search and seize has been discredited.”
  See Berger v. New York, 388 U. S. 41, 44, 50-53, 64; Clinton v. Virginia, 377 U. S. 158; Lopez v. United States, 373 U. S. 427, 437-439; Silverman v. United States, supra, at 510-512.
  See also DeStefano v. Woods, 392 U. S. 631; Johnson v. New Jersey, 384 U. S. 719, 727; Tehan v. Shott, 382 U. S. 406, 413; Linkletter v. Walker, 381 U. S. 618, 629.
  See Roberts v. Russell, 392 U. S. 293, 295; Witherspoon v. Illinois, 391 U. S. 510, 523, n. 22.
  In other areas where retroactivity has been denied the “purpose” criterion offered much weaker support. Cf. Stovall v. Denno, 388 U. S. 293, 298, where it was conceded that “the Wade and Gilbert rules also are aimed at avoiding unfairness at the trial by enhancing the reliability of the fact-finding process in the area of identification evidence”; Johnson v. New Jersey, 384 U. S. 719, 730, where it was recognized that “Escobedo and Miranda guard against the possibility of unreliable statements in every instance of in-custody interrogation”; and Tehan v. Shott, 382 U. S. 406, 414, where it was stated that “the ‘purpose’ of the Griffin rule is to be found in the whole complex of values that the privilege against self-incrimination itself represents,” including “our realization that the privilege, while sometimes ‘a shelter to the guilty/ is often ‘a protection to the innocent.’ ” Id., at 414-415, n. 12.
  Jackson v. Demo, 378 U. S. 368; Gideon v. Wainwright, 372 U. S. 335; Griffin v. Illinois, 351 U. S. 12.
  48 Stat. 1103, 47 U. S. C. § 605.
  The Government has informed us in its brief that “[i]nstead of a wholesale release of thousands of convicted felons, only a relatively small number would probably be affected [by a retroactive application of Katz], since electronic surveillance has played a part in a limited number of federal cases.”
  We noted in Berger v. New York, 388 U. S. 41, 48-49, that only a handful of States have prohibited or regulated electronic surveillance by law enforcement officials.
  See DeStefano v. Woods, 392 U.S. 631; Stovall v. Denno, 388 U. S. 293; Johnson v. New Jersey, 384 U. S. 719. Cf. cases cited in n. 13, supra.
  In Linkletter itself the Court noted that it dealt only with the narrow issue whether Mapp should be applied to final as well as nonfinal convictions:
  “[Mapp] has also been applied to cases still pending on direct review at the time it was rendered. Therefore, in this case, we are concerned only with whether the exclusionary principle enunciated in Mapp applies to state court convictions which had become final before rendition of our opinion.” 381 U. S., at 622.
  Mapp had already been applied in Ker v. California, 374 U. S. 23; Fahy v. Connecticut, 375 U. S. 85; Stoner v. California, 376 U. S. 483. Griffin had been applied in O’Connor v. Ohio, 382 U. S. 286, shortly before Tehan was decided.
  Actually, Mapp was, of course, decided under the Fourth and Fourteenth Amendments, with one member of the five-man majority relying at least in part on the Fifth Amendment. 367 U. S., at 661-666 (Black, J., concurring).
  Johnson v. New Jersey, 384 U. S. 719, 731. And see Tehan v. Shott, 382 U. S. 406, 417.
  Indeed, since the Fourth Amendment prohibits only unreasonable searches and seizures, it could be argued that there was, in fact, no Fourth Amendment violation in the present case. The law enforcement officers could certainly be said to have been acting “reasonably” in measuring their conduct by the relevant Fourth Amendment decisions of this Court. Cf. Katz v. United States, 389 U. S. 347, 356; James v. United States, 366 U. S. 213, 221-222, 245.
  The dissenting opinion of Me. Justice Fortas suggests that our holding today denies “the benefit of a fundamental constitutional provision, and not merely of court-made rules implementing a constitutional mandate.” Post, at 271. To the contrary, we simply decline to extend the court-made exclusionary rule to cases in which its deterrent purpose would not be served. The exclusionary rule “has no bearing on guilt” or “the fairness of the trial.” Linkletter v. Walker, 381 U. S., at 638, 639.
  Of course, Katz himself benefited from the new principle announced on that date, and, as our Brother Douglas observes, to that extent the decision has not technically been given wholly prospective application. But, as we recently explained in Stovall v. Denno, 388 U. S. 293, 301, the fact that the parties involved in the decision are the only litigants so situated who receive the benefit of the new rule is “an unavoidable consequence of the necessity that constitutional adjudications not stand as mere dictum.” Whatever inequity may arguably result from applying the new rule to those “chance beneficiaries” is “an insignificant cost for adherence to sound principles of decision-making.” Ibid.