with, whom Mr. Justice Marshall joins, dissenting.
I
Until today the question of the prospective application of a decision of this Court was not deemed to be presented unless the decision “constitute[d] a sharp break in the line of earlier authority or an avulsive change which caused the current of the law thereafter to flow between new banks.” Hanover Shoe, Inc. v. United Shoe Machinery Corp., 392 U. S. 481, 499 (1968).1 Measured by that test, our decision in Almeida-Sanchez v. United States, 413 U. S. 266 (1973), presents no question of prospectivity, and the Court errs in even addressing the question. For both the Court’s opinion and the concurring opinion of Mr. Justice Powell in AlmeidaSanchez plainly applied familiar principles of constitutional adjudication announced 50 years ago in Carroll v. United States, 267 U. S. 132, 153-154 (1925), and merely construed 66 Stat. 233, 8 U. S. C. § 1357 (a)(3), so as to render it constitutionally consistent with that decision. 413 U. S., at 272; id., at 275, and n. 1 (Powell, J., concurring).
The Court states, however, that the Border Patrol agents searched Peltier “in reliance upon a validly enacted statute, supported by longstanding administrative regulations and continuous judicial approval. . . .” Ante, *545at 541. With all respect, any such reliance would be misplaced. First, the Court repeats the error of my Brother White in his dissent in Almeida-Sanchez in finding express congressional and administrative approval for random roving patrol searches. 413 U. S., at 291, 292-293, 296. The statute, 8 U. S. C. § 1357 (a), only authorizes searches of vehicles “without warrant . . . within a reasonable distance from any external boundary” ; nothing in the statute expressly dispenses with the necessity for showing probable cause. The regulation, 8 CFR § 287.1 (a) (2) (1973), merely defined “a reasonable distance” as “within 100 air miles”; it, too, does not purport to exempt the Border Patrol from observing the probable-cause requirement.2
Second, the Court states that “[b]etween 1952 and Almeida-Sanchez, roving Border Patrol searches under § 287 (a)(3) were upheld repeatedly against constitutional attack.” Ante, at 540. But the first decision of the Court of Appeals for the Ninth Circuit squarely in point, United States v. Miranda, 426 F. 2d 283, was decided in 1970, and the second, United States v. Almeida*546Sanchez, 452 F. 2d 459, was decided over strong dissent in 1971 and was pending on certiorari in this Court when Peltier was searched. 406 U. S. 944 (1972). The first decision of the Court of Appeals for the Tenth Circuit approving alien searches by roving patrols without either probable cause or any suspicious conduct was in 1969. Roa-Rodriquez v. United States, 410 F. 2d 1206. And the Court of Appeals for the Fifth Circuit, unlike the Ninth and Tenth Circuits, always required at least a “reasonable suspicion” that a car might contain aliens as the basis of a valid search under 8 U. S. C. § 1357 (a) (3). United States v. Wright, 476 F. 2d 1027, 1030, and n. 2 (1973), and cases cited.
In addition, the rule of Miranda, supra, was a patent anomaly in the Courts of Appeals which sanctioned roving patrol searches without a showing even of suspicious circumstances. The Court of Appeals for the Ninth Circuit, for example, held consistently that probable cause must be shown to validate a search for contraband except in a border search or its functional equivalent, see, e. g., Cervantes v. United States, 263 F. 2d 800, 803 (1959); Fumagalli v. United States, 429 F. 2d 1011 (1970),3 and this despite a statutory authorization to search for contraband at least as broad as § 1357 (a) *547(3). See 14 Stat. 178, 19 U. S. C. § 482.4 Moreover, the Courts of Appeals require some measure of cause to suspect violation of law in interrogations and arrests authorized by other subsections of 8 U. S. C. § 1357 (a). See Au Yi Lau v. INS, 144 U. S. App. D. C. 147, 445 F. 2d 217 (1971); Yam Sang Kwai v. INS, 133 U. S. App. D. C. 369, 411 F. 2d 683 (1969).
Given this history, it becomes quite clear why the Court has found it necessary to discard the “sharp break” test to reach the prospectivity question in this case. For the approval by Courts of Appeals of this law enforcement practice was short-lived, less than unanimous, irreconcilable with other rulings of the same courts, and contrary to the explicit doctrine of this Court in Carroll, supra, as reaffirmed in Brinegar v. United States, 338 U. S. 160, 164 (1949), and other cases. If a case in this Court merely reaffirming longstanding precedent can ever constitute the “avulsive change [in] the current of the law” required before we even address the issue of prospectivity, Hanover Shoe, 392 U. S., at 499, surely Almeida-Sanchez was not such a case.5
*548This case is a good illustration of the dangers of addressing prospectivity where the “sharp break” standard is not met. As this Court has recognized, applying a decision only prospectively,6 can entail inequity to others whose cases are here on direct review but are held pending decision of the case selected for decision. Stovall v. Denno, 388 U. S. 293, 301 (1967). Although I continue to believe that denial of the benefits of the decision in such cases is a tolerable anomaly in cases in which defendants *549were accorded all constitutional rights then announced by this Court, it becomes intolerable, and a travesty of justice, when the Court does no more than reaffirm and apply long-established constitutional principles to correct an aberration created by the courts of appeals.
More fundamentally, applying a decision of this Court prospectively when the decision is not a “sharp break in the web of the law,” Milton v. Wainwright, 407 U. S. 371, 381 n. 2 (1972) (Stewart, J., dissenting), encourages in those responsible for law enforcement a parsimonious approach to enforcement of constitutional rights. “One need not be a rigid partisan of Blackstone to recognize that many, though not all, of this Court’s constitutional decisions are grounded upon fundamental principles whose content does not change dramatically from year to year . . . .” Desist v. United States, 394 U. S. 244, 263 (1969) (Harlan, J., dissenting). To apply our opinions prospectively except in “sharp break” cases “add[s] this Court’s approval to those who honor the Constitution’s mandate only where acceptable to them or compelled by the precise and inescapable specifics of a decision of this Court. . . . History does not embrace the years needed for us to hold, millimeter by millimeter, that such and such a penetration of individual rights is an infringement of the Constitution’s guarantees. The vitality of our Constitution depends upon conceptual faithfulness and not merely decisional obedience. Certainly, this Court should not encourage police or other courts to disregard the plain purport of our decisions and to adopt a let’s-wait-until-it’s-decided approach.” Id., at 277 (Fortas, J., dissenting).7
*550II
Nevertheless, the Court substitutes, at least as respects the availability of the exclusionary rule in cases involving searches invalid under the Fourth Amendment, a presumption against the availability of decisions of this Court except prospectively. The substitution discards not only the “sharp break” determinant but also the equally established principle that prospectivity “is not automatically determined by the provision of the Constitution on which the dictate is based. . . . [W]e must determine retroactivity ‘in each case’ by looking to the peculiar traits of the specific ‘rule in question.’ ” Johnson v. New Jersey, 384 U. S. 719, 728 (1966).8 Link-letter v. Walker, 381 U. S. 618 (1965), the seminal prospectivity decision, held only that “the Court may in the interest of justice make [a] rule prospective . . . where the exigencies of the situation require such an application.” Id., at 628 (emphasis added). Today the Court stands the Linkletter holding on its head by creating a class of cases in which nonretroactivity is the rule and not, as heretofore, the exception.
The Court’s stated reason for this remarkable departure from settled principles is “the policies underlying the [exclusionary] rule.” Ante, at 534-535. But the policies identified by the Court as underlying that rule in Fourth Amendment cases are distorted out of all resemblance to the understanding of purposes that has heretofore prevailed. I said in my dissent in United States v. Calandra, 414 U. S. 338 (1974), that that decision left' *551me “with the uneasy feeling that ... a majority of my colleagues have positioned themselves to . . . abandon altogether the exclusionary rule in search-and-seizure cases.” Id., at 365. My uneasiness approaches conviction after today’s treatment of the rule.
Ill
The Court’s opinion depends upon an entirely new understanding of the exclusionary rule in Fourth Amendment cases, one which, if the vague contours outlined today are filled in as I fear they will be, forecasts the complete demise of the exclusionary rule as fashioned by this Court in over 61 years of Fourth Amendment jurisprudence. See Weeks v. United States, 232 U. S. 383 (1914).9 An analysis of the Court’s unsuccessfully veiled reformulation demonstrates that its apparent rush to discard 61 years of constitutional development has produced a formula difficult to comprehend and, on any understanding of its meaning, impossible to justify.
The Court signals its new approach in these words: “If the purpose of the exclusionary rule is to deter unlawful police conduct, then evidence obtained from a search should be suppressed only if it can be said that the law enforcement officer had knowledge, or may properly be charged with knowledge, that the search was unconstitutional under the Fourth Amendment.” Ante, at 542. True, the Court does not state in so many words that this formulation of the exclusionary rule is to be applied beyond the present retroactivity context. But the proposition is stated generally and, particularly in view of *552the concomitant expansion of prospectivity announced today, Part I, supra, I have no confidence that the new formulation is to be confined to putative retroactivity cases. Rather, I suspect that when a suitable opportunity arises, today’s revision of the exclusionary rule will be pronounced applicable to all search-and-seizure cases. I therefore register my strong disagreement now.
The new formulation obviously removes the very foundation of the exclusionary rule as it has been expressed in countless decisions. Until now the rule in federal criminal cases decided on direct review10 has been that suppression is necessarily the sanction to be applied when it is determined that the evidence was in fact illegally acquired.11 The revision unveiled today *553suggests that instead of that single inquiry, district judges may also have to probe the subjective knowledge of the official who orders the search, and the inferences from existing law that official should have drawn.12 The decision whether or not to order suppression would then turn upon whether, based on that expanded inquiry, suppression would comport with either the deterrence rationale of the exclusionary rule or “the imperative of judicial integrity.” 13
*554On this reasoning, Almeida-Sanchez itself was wrongly-decided. For if the Border Patrolmen who searched Peltier could not have known that they were acting unconstitutionally, and thus could not have been deterred from the search by the possibility of the exclusion of the evidence from the trial, obviously the Border Patrolmen who searched Almeida-Sanchez several years earlier had no reason to be any more percipient. If application of the exclusionary rule depends upon a showing that the particular officials who conducted or authorized a particular search knew or should have known that they were violating a specific, established constitutional right, the reversal of Almeida-Sanchez’ conviction was plainly error.
Other defects of today’s new formulation are also patent. First, this new doctrine could stop dead in its tracks judicial development of Fourth Amendment rights. For if evidence is to be admitted in criminal trials in the absence of clear precedent declaring the search in question unconstitutional, the first duty of a court will be to deny the accused’s motion to suppress if he cannot cite a case invalidating a search or seizure on identical facts.14 Yet, even its opponents concede *555that the great service of the exclusionary rule has been its usefulness in forcing judges to enlighten our understanding of Fourth Amendment guarantees. “It is . . . imperative to have a practical procedure by which courts can review alleged violations of constitutional rights and articulate the meaning of those rights. The advantage of the exclusionary rule — entirely apart from any direct deterrent effect — is that it provides an occasion for judicial review, and it gives credibility to the constitutional guarantees. By demonstrating that society will attach serious consequences to the violation of constitutional rights, the exclusionary rule invokes and magnifies the moral and educative force of the law. Over the long term this may integrate some fourth amendment ideals into the value system or norms of behavior of law enforcement agencies.” Oaks, Studying the Exclusionary Rule in Search and Seizure, 37 U. Chi. L. Rev. 665, 756 (1970) (hereafter Oaks). See also Amsterdam, Perspectives on the Fourth Amendment, 58 Minn. L. Rev. 349, 429-430 (1974) (hereafter Amsterdam) . While distinguished authority has suggested that an effective affirmative remedy could equally serve that function, see Oaks, supra, and Bivens v. Six Unknown Federal Narcotics Agents, 403 U. S. 388, 420-423 (1971) (Burger, C. J., dissenting), no equally effective alternative has yet been devised.
*556Second, contrary to the Court’s assumption, the exclusionary rule does not depend in its deterrence rationale on the punishment of individual law enforcement officials.15 Indeed, one general fallacy in the reasoning of critics of the exclusionary rule is the belief that the rule is meant to deter official wrongdoers by punishment or threat of punishment. It is also the fallacy of the Court’s attempt today to outline a revision in the exclusionary rule.
Deterrence can operate in several ways. The simplest is special or specific deterrence — -punishing an individual so that he will not repeat the same behavior. But “[t]he exclusionary rule is not aimed at special deterrence since it does not impose any direct punishment on a law enforcement official who has broken the rule. . . . The exclusionary rule is aimed at affecting the wider audience of all law enforcement officials and society at *557large. It is meant to discourage violations by individuals who have never experienced any sanction for them.” Oaks 709-710.16
Thus, the exclusionary rule, focused upon general, not specific, deterrence, depends not upon threatening a sanction for lack of compliance but upon removing an inducement to violate Fourth Amendment rights. Elkins v. United States, 364 U. S. 206, 217 (1960), clearly explained that the exclusionary rule’s “purpose is to deter— to compel respect for the constitutional guaranty in the only effectively available way — by removing the incentive to disregard it.” (Emphasis added.) “A criminal court system functioning without an exclusionary rule ... is the equivalent of a government purchasing agent paying premium prices for evidence branded with the stamp of unconstitutionality. ... If [the Government] receives the products of [illegal] searches and seizures . . . and uses them as the means of convicting people whom the officer conceives it to be his job to get convicted, it is not merely tolerating but inducing unconstitutional *558searches and seizures.” Amsterdam 431-432.17 (Emphasis supplied.)
We therefore might consider, in this light, what may have influenced the officials who authorized roving searches without probable cause under the supposed authority of 8 U. S. C. § 1357 (a) (3) and 8 CFR § 287.1 (a) (2) (1973).18 The statute is at best ambiguous as to *559whether probable cause is required, though quite explicit that a warrant is not.19 The officials could therefore read the statute in one of two ways. They could read it not to require probable cause, regard as irrelevant Carroll v. United States, 267 U. S. 132 (1925), requiring probable cause, though no warrant, before stopping and searching a moving automobile unless the search is at the border, and command their subordinates to stop at random any car within 100 miles of the border and search for illegal aliens. Or they could conclude that because the statute is silent about probable cause, and because Carroll seems to require it, they should instruct their subordinates to stop moving vehicles away from the border only if there is some good reason to believe that they contain illegal aliens. Obviously, today’s decision is a wide-open invitation to pursue the former course, because if this Court later decides that the officers guessed wrong in a particular case, one conviction will perhaps be lost, but many will have been gained, see supra, at 549, 554. The concept of the exclusionary rule until today, however, was designed to discourage officials from invariably opting for the choice that compromises Fourth Amendment rights, even though that rule has not worked perfectly as it did not in this case. “The efforts of the courts and their officials to bring the guilty to punishment, praiseworthy as they are, are not to be aided by the sacrifice of those great principles established by years of endeavor and *560suffering which have resulted in their embodiment in the fundamental law of the land.” Weeks, 232 U. S., at 393 (emphasis supplied).
Aside from this most fundamental error, solid practical reasons militate forcefully in favor of rejection of today’s suggested road to revision of the exclusionary rule. This Court has already rejected a case-by-case approach to the exclusionary rule. After Wolf v. Colorado, 338 U. S. 25 (1949), had held the Fourth Amendment applicable to the States without also requiring the States to follow the exclusionary rule of Weeks, Irvine v. California, 347 U. S. 128 (1954), presented the opportunity of compelling the States to apply Weeks in especially egregious situations such as Irvine’s. The Court rejected the opportunity because “a distinction of the kind urged would leave the rule so indefinite that no state court could know what it should rule in order to keep its processes on solid constitutional ground.” Id., at 134 (opinion of Jackson, J.). See also id., at 138 (Clark, J., concurring).
Today’s formulation extended to all search-and-seizure cases would inevitably introduce the same uncertainty, by adding a new layer of factfinding in deciding motions to suppress in the already heavily burdened federal courts. The district courts would have to determine, and the appellate courts to review, subjective states of mind of numerous people, see n. 18, supra, and reasonable objective extrapolations of existing law, on each of the thousands of suppression motions presented each year.20 Nice questions will have to be faced, such as whether to exclude evidence obtained in a search which officers be*561lieved to be unconstitutional but which in fact was not, and whether to exclude evidence obtained in a search in fact unconstitutional and believed to be unconstitutional, but which the ordinary, reasonable police officer might well have believed was constitutional. One criticism of the present formulation of the exclusionary rule is that it may deflect the inquiry in a criminal trial from the guilt of the defendant to the culpability of the police. The formulation suggested today would vastly exacerbate this possibility, heavily burden the lower courts, and worst of all, erode irretrievably the efficacy of the exclusion principle.21 Indeed, “no [federal] court could know what it should rule in order to keep its processes on solid constitutional ground.” Cf. 347 U. S., at 134. Because of the superficial and summary way that the Court treats the question the formulation will, I am certain, be unsatisfactory even to those convinced, as I am not, that the exclusionary rule must be drastically overhauled.22
If a majority of my colleagues are determined to discard the exclusionary rule in Fourth Amendment cases, they should forthrightly do so, and be done with it. This business of slow strangulation of the rule, with no *562opportunity afforded parties most concerned to be heard, would be indefensible in any circumstances. But to attempt covertly the erosion of an important principle over 61 years in the making as applied in federal courts clearly demeans the adjudicatory function, and the institutional integrity of this Court.
This requirement has been variously stated. See, e. g., Desist v. United States, 394 U. S. 244, 248 (1969) (“a clear break with the past”); Milton v. Wainwright, 407 U. S. 371, 381 n. 2 (1972) (Stewart, J., dissenting) ("a sharp break in the web of the law”) ; Chevron Oil Co. v. Huson, 404 U. S. 97, 106 (1971) (“the decision to be applied nonretroactively must establish a new principle of law, either by overruling clear past precedent on which litigants may have relied ... or by deciding an issue of first impression whose resolution was not clearly foreshadowed . ..”).
Nor is there anything in the legislative history of § 1357 (a) which suggests that Congress intended to authorize the Border Patrol to stop any car in motion within 100 miles of a border. See H. R. Rep. No. 186, 79th Cong., 1st Sess., 2 (1945); S. Rep. No. 632, 79th Cong., 1st Sess., 2 (1945). See also United States v. Almeida-Sanchez, 452 F. 2d 459, 465 (CA9 1971) (Browning, J., dissenting): “The more reasonable interpretation of a statute of this sort is not that it defines a constitutional standard of reasonableness for searches by the government agents to whom it applies, but rather that it delegates authority to be exercised by those agents in accordance with constitutional limitations. . . . The statute authorizes the officers to conduct such searches — and a search within the statute’s terms is not illegal as beyond the officer’s statutory authority. But a search within the literal language of the [statute] is nonetheless barred if it violates the Fourth Amendment. See, e. g., Boyd v. United States, 116 U. S. 616 . . . (1886).”
In Cervantes, the court said: “The government . . . appears to accept appellant’s proposition that the reasonableness of a search made of an automobile on the highway and its driver depends upon a showing of probable cause. . . . That this is the proper test of the reasonableness of such a search, see Carroll v. United States, supra, 267 U. S., at pages 155-156 . . . .” 263 F. 2d, at 803, and n. 4. Despite this general language, Cervantes was later summarily distinguished as applying only to searches for contraband, and not to searches for aliens. Fumagalli v. United States, 429 F. 2d, at 1013. No attempt was ever made to explain how a search for aliens could be distinguished under Carroll from a search for contraband. See United States v. Almeida-Sanchez, 452 F. 2d, at 464 (Browning, J., dissenting).
Title 19 U. S. C. §482 provides in pertinent part: “Any of the officers or persons authorized to board or search vessels may stop, search, and examine, as well without as within their respective districts, any vehicle, ... or person, on which or whom he or they shall suspect there is merchandise which is subject to duty, or shall have been introduced into the United States in any manner contrary to law . . . .”
“In order to avoid conflict between this statute and the Fourth Amendment, the statutory language has been restricted by the courts to 'border searches.’ ” United States v. Weil, 432 F. 2d 1320, 1323 (CA9 1970).
Most cases where the Court has ordained prospective application of a new rule of criminal procedure have involved decisions which explicitly overruled a previous decision of this Court. See Link-letter v. Walker, 381 U. S. 618 (1965), involving the retroactivity of Mapp v. Ohio, 367 U. S. 643 (1961), which had overruled Wolf v. *548Colorado, 338 U. S. 25 (1949); Williams v. United States, 401 U. S. 646 (1971), involving the retroactivity of Chimel v. California, 395 U. S. 752 (1969), which overruled United States v. Rabinowitz, 339 U. S. 56 (1950), and Harris v. United States, 331 U. S. 145 (1947); Fuller v. Alaska, 393 U. S. 80 (1968) (per curiam), involving the retroactivity of Lee v. Florida, 392 U. S. 378 (1968), which overruled Schwartz v. Texas, 344 U. S. 199 (1952); Desist v. United States, 394 U. S. 244 (1969), involving the retroactivity of Katz v. United States, 389 U. S. 347 (1967), which specifically rejected Goldman v. United States, 316 U. S. 129 (1942), and Olmstead v. United States, 277 U. S. 438 (1928); Tehan v. United States ex rel. Shott, 382 U. S. 406 (1966), involving the retroactivity of Griffin v. California, 380 U. S. 609 (1965), which overruled Twining v. New Jersey, 211 U. S. 78 (1908); Daniel v. Louisiana, 420 U. S. 31 (1975), involving the retroactivity of Taylor v. Louisiana, 419 U. S. 522 (1975), which specifically disapproved Hoyt v. Florida, 368 U. S. 57 (1961).
In other instances, the practice recently disapproved had, at least arguably, been sanctioned previously by this Court. See Johnson v. New Jersey, 384 U. S. 719, 731 (1966); Gosa v. Mayden, 413 U. S. 665, 673 (1973) (opinion of Blackmun, J.); Adams v. Illinois, 405 U. S. 278 (1972).
Finally, in another group of cases, the rule applied prospectively was merely a prophylactic one, designed by this Court to protect underlying rights already announced and applicable retroactively. See Halliday v. United States, 394 U. S. 831 (1969) (per curiam); Stovall v. Denno, 388 U. S. 293 (1967); Michigan v. Payne, 412 U. S. 47 (1973).
Of course, we have always given the benefit of a criminal procedure decision to the defendant in whose case the principle was announced. See Stovall v. Denno, supra, at 301.
1 continue to believe that Mr. Justice Harlan and Mr. Justice Fortas were in error in Desist itself, because Katz v. United States, supra, did overrule clear past precedent of this Court. But I think that the prophecy of horrors by the dissenters in Desist has, with the Court's opinion today, come true.
See also Michigan v. Tucker, 417 U. S. 433, 453 n. 26 (1974): “Under the framework of the analysis established in Linkletter, supra, and in subsequent cases, it would seem indispensable to understand the basis for a constitutional holding of the Court in order to later determine whether that holding should be retroactive.”
The exclusionary rule in federal cases has roots that antedate even Weeks. Twenty-eight years before that decision, in Boyd v. United States, 116 U. S. 616 (1886), the Court held that the admission into evidence of papers acquired by the Government in violation of the Fourth Amendment was unconstitutional. Id., at 638.
1 emphasize that this is a federal criminal case, and that the exclusionary rule issue comes to us on direct review. Thus, neither Mapp v. Ohio, 367 U. S. 643 (1961), applying the Fourth Amendment exclusionary rule to the States, nor Kaufman v. United States, 394 U. S. 217 (1969), permitting Fourth Amendment exclusionary rule issues to be raised for the first time in collateral proceedings, is here involved. While abandonment of both Mapp and Kaufman has at times been advocated, no Justice has intimated that Weeks should also be overruled, at least in the absence of suitable and efficacious substitute remedies. See, on Mapp, Coolidge v. New Hampshire, 403 U. S. 443, 490 (1971) (Harlan, J., concurring); id., at 492 (Burger, C. J., dissenting in part and concurring in part); id., at 493 (Black, J., concurring and dissenting); id., at 510 (statement of Blackmun, J.); on Kaufman, see Schneckloth v. Bustamonte, 412 U. S. 218, 250 (1973) (Powell, J., joined by Burger, C. J., and Rehnquist, J., concurring); see also, id., at 249 (Blackmun, J., concurring). But see, on Weeks, Bivens v. Six Unknown Federal Narcotics Agents, 403 U. S. 388, 420-421 (1971) (Burger, C. J., dissenting) ; Schneckloth, supra, at 267-268, n. 25 (Powell, J., concurring).
Wolf v. Colorado, 338 U. S. 25, 28 (1949), summarized Weeks as follows: “In Weeks v. United States, supra, this Court held that in a federal prosecution the Fourth Amendment barred the use of evidence secured through an illegal search and seizure.” (Emphasis *553added.) Elkins v. United States, 364 U. S. 206, 212-213 (1960), again confirmed the Weeks rule, “[e]vidence which had been seized by federal officers in violation of the Fourth Amendment [ean]not be used in a federal criminal prosecution” (emphasis added), and expanded it to cover “evidence obtained by state officers during a search which, if conducted by federal officers, would have violated the defendant’s immunity from unreasonable searches and seizures under the Fourth Amendment,” id., at 223 (emphasis added); see also id., at 222. Similarly, Ker v. California, 374 U. S. 23, 30 (1963), stated that the exclusionary rule “forbids the Federal Government to convict a man of crime by using testimony or papers obtained from him by unreasonable searches and seizures as defined in the Fourth Amendment” (emphasis supplied); see also id., at 34. Thus, the test whether evidence should be suppressed in federal court has always been solely whether the Fourth Amendment prohibition against “unreasonable” searches and seizures was violated, nothing more and nothing less. See also, e. g., Alderman v. United States, 394 U. S. 165, 176 (1969); United States v. Calandra, 414 U. S. 338, 347 (1974).
To be sure, the very vagueness of the intimated reformulation as articulated today leaves unclear exactly what showing demonstrates that a law enforcement officer “may properly be charged with knowledge, that the search was unconstitutional.” In this case, for example, could the Border Patrol, a national organization, have been charged with knowledge of the unconstitutionality of an Almeida-Sanchez type search if the courts of appeals were in clear conflict on whether probable cause was required?
It is gratifying that the Court at least verbally restores to exclusionary-rule analysis this consideration, which for me is the core value served by the exclusionary rule. See Harris v. New *554York, 401 U. S. 222, 231-232 (1971) (Brennan, J., dissenting); United States v. Calandra, supra, at 355 (Brennan, J., dissenting). But the Court’s treatment of this factor is wholly unsatisfactory. See id., at 359-360 (Brennan, J., dissenting). I need discuss the question no further, however, since the Court merges the “imperative of judicial integrity” into its deterrence rationale, ante, at 538, and then ignores the imperative when it applies its new theory to the facts of this case, see Part II of the Court’s opinion. Rather, I show in the text that, on the Court’s own deterrence rationale alone, today’s suggested reformulation would be a disaster.
Angelet v. Fay, 381 U. S. 654 (1965), declined to decide whether Mapp v. Ohio, 367 U. S. 643 (1961), would bar federal agents from testifying in a state court concerning illegally obtained *555evidence, because Mapp was held in Linkletter v. Walker, 381 U. S. 618 (1965), to be nonretroactive. Somewhat similarly, Michigan v. Tucker, 417 U. S. 433 (1974), refused to decide whether Miranda v. Arizona, 384 U. S. 436 (1966), applies to exclude the testimony of a witness discovered as a result of a statement given after incomplete Miranda warnings, because the interrogation in Tucker occurred before Miranda. See also Michigan v. Payne, 412 U. S., at 49-50, n. 3. Thus, there is clear precedent for avoiding decision of a constitutional issue raised by police behavior when in any event the evidence was admissible in the particular case at bar.
Critics of the exclusionary rule emphasize that in actual operation law enforcement officials are rarely reprimanded, discharged, or otherwise disciplined when evidence is excluded at trial for search- and-seizure violations. While this fact, to the extent it is true, may limit the efficacy of the exclusionary rule, it does not, for the reasons stated in the text, prove it useless. Suggestions are emerging for tailoring the exclusionary rule to the adoption and enforcement of regulations and training procedures concerning searches and seizures by law enforcement agencies. Amsterdam 409 et seq.; Kaplan, The Limits of the Exclusionary Rule, 26 Stan. L. Rev. 1027, 1050 et seq. (1974). Today’s approach, rather than advancing this goal, would diminish the incentive for law enforcement agencies to train and supervise subordinate officers. See id., at 1044. At any rate, to the extent law enforcement agencies do visit upon individual employees consequences for conducting searches and seizures which are later held illegal, the agencies can be expected to take account of the degree of departure from existing norms as elucidated in court decisions. Thus, there is no need for the courts to adjust the exclusionary rule in order to assure fairness to individual officials or to promote decisiveness.
See also Amsterdam 431:
“The common focus on the concept of ‘deterrence’ in the debate over the exclusionary rule can be quite misleading. It suggests that the police have a God-given inclination to commit unconstitutional searches and seizures unless they are ‘deterred’ from that behavior. Once this assumption is indulged, it is easy enough to criticize the rule excluding unconstitutionally obtained evidence on the ground that it ‘does not apply any direct sanction to the individual officer whose illegal conduct results in the exclusion/ and so cannot ‘deter’ him. But no one, to my knowledge, has ever urged that the exclusionary rule is supportable on this principle of ‘deterrence.’ It is not supposed to ‘deter’ in the fashion of the law of larceny, for example, by threatening punishment to him who steals a television set — a' theory of deterrence, by the way, whose lack of empirical justification makes the exclusionary rule look as solid by comparison as the law of gravity.”
See also Oaks 711:
“‘The act is branded as reprehensible by authorized organs of society/ Andenaes states, 'and this official branding of the conduct may influence attitudes quite apart from the fear of sanctions.’ The existence and imposition of a sanction reinforces the rule and underlines the importance of observing it. The principle is directly applicable to the exclusionary rule. The salient defect in the rule of Wolf v. Colorado was the difficulty of persuading anyone that the guarantees of the fourth amendment were seriously intended and important when there was no sanction whatever for their violation. As a visible expression of social disapproval for the violation of these guarantees, the exclusionary rule makes the guarantees of the fourth amendment credible. Its example teaches the importance attached to observing them.”
I assume that the Court’s statement that “the purpose of the exclusionary rule is to deter unlawful police conduct,” ante, at 542, does not imply that deterrence can work only at the level of the individual officers on the scene, nor suggest that under its approach only the knowledge, real or constructive, of the official conducting the search is relevant. Fourth Amendment violations become more, not less, reprehensible when they are the product of Government policy rather than an individual policeman’s errors of judgment. See Alderman v. United States, 394 U. S., at 203 (Fortas, J., concurring in part and dissenting in part).
“[T]he Fourth Amendment was intended to secure the citizen in person and property against unlawful invasion of the sanctity of his home by officers of the law acting under legislative or judicial sanction. This protection is equally extended to the action of the Government and officers of the law acting under it. . . .” Weeks v. United States, 232 U. S. 383, 394 (1914). (Emphasis supplied.) Obviously, any rule intended to prevent Fourth Amendment violations must operate not only upon individual law enforcement officers *559but also upon those who set policy for them and approve their actions. Otherwise, for example, evidence derived from any search under a warrant could be admissible, because the searching policeman, having had a warrant approved by the designated judicial officer, had every reason to believe the warrant valid. Certainly, the Court can intend no such result, and would have lower courts inquire into the frame of mind, actual and constructive, of all officials whose actions were relevant to the search.
See supra, at 545, and n. 2.
In addition, adding “one more factfinding operation, and an especially difficult one to administer, to those already required of [the] lower judiciary” could add a factor of discretion to the operation of the exclusionary rule impossible for the appellate courts effectively to control. Kaplan, supra, n. 15, at 1045.
Indeed, Congress in recent years has declined to take steps somewhat similar to those now proposed. See Canon, Is the Exclusionary Rule in Failing Health? Some New Data and a Plea Against a Precipitous Conclusion, 62 Ky. L. J. 681, 694-696 (1974).
For example, the modification of the exclusionary rule most discussed recently has been that in the ALI Model Code of PreArraignment Procedure §290.2 (2) (Prop. Off. Draft No. 1, 1972). See Bivens, 403 U. S., at 424 (Appendix to opinion of Burger, C. J., dissenting); Canon, supra, n. 21, at 694^696. While the ALI proposal raises many of the same questions I have outlined above, it differs substantially from the Court’s proposed approach, since it takes into account many factors besides “(c) the extent to which the violation was willful.”