THE PROGRESSIVE VOICE OF REFORM

U.S. Supreme Court

ILLINOIS v. GATES, 462 U.S. 213 (1983)

462 U.S. 213

ILLINOIS v. GATES ET UX.
CERTIORARI TO THE SUPREME COURT OF ILLINOIS

No. 81-430.

Argued October 13, 1982 Reargued March 1, 1983
Decided June 8, 1983

On May 3, 1978, the Police Department of Bloomingdale, Ill., received an anonymous letter which included statements that respondents, husband and wife, were engaged in selling drugs; that the wife would drive their car to Florida on May 3 to be loaded with drugs, and the husband would fly down in a few days to drive the car back; that the car's trunk would be loaded with drugs; and that respondents presently had over $100,000 worth of drugs in their basement. Acting on the tip, a police officer determined respondents' address and learned that the husband made a reservation on a May 5 flight to Florida. Arrangements for surveillance of the flight were made with an agent of the Drug Enforcement Administration (DEA), and the surveillance disclosed that the husband took the flight, stayed overnight in a motel room registered in the wife's name, and left the following morning with a woman in a car bearing an Illinois license plate issued to the husband, heading north on an interstate highway used by travelers to the Bloomingdale area. A search warrant for respondents' residence and automobile was then obtained from an Illinois state-court judge, based on the Bloomingdale police officer's affidavit setting forth the foregoing facts and a copy of the anonymous letter. When respondents arrived at their home, the police were waiting and discovered marihuana and other contraband in respondents' car trunk and home. Prior to respondents' trial on charges of violating state drug laws, the trial court ordered suppression of all the items seized, and the Illinois Appellate Court affirmed. The Illinois Supreme Court also affirmed, holding that the letter and affidavit were inadequate to sustain a determination of probable cause for issuance of the search warrant under Aguilar v. Texas, 378 U.S. 108, and Spinelli v. United States, 393 U.S. 410, since they failed to satisfy the "two-pronged test" of (1) revealing the informant's "basis of knowledge" and (2) providing sufficient facts to establish either the informant's "veracity" or the "reliability" of the informant's report.

REHNQUIST, J., delivered the opinion of the Court, in which BURGER, C. J., and BLACKMUN, POWELL, and O'CONNOR, JJ., joined. WHITE, J., filed an opinion concurring in the judgment, post, p. 246. BRENNAN, J., filed a dissenting opinion, in which MARSHALL, J., joined, post, p. 274. STEVENS, J., filed a dissenting opinion, in which BRENNAN, J., joined, post, p. 291.

Paul P. Biebel, Jr., First Assistant Attorney General of Illinois, reargued the cause for petitioner. With him on the briefs on reargument were Tyrone C. Fahner, former Attorney General, Neil F. Hartigan, Attorney General, Michael A. Ficaro and Morton E. Friedman, Assistant Attorneys General, Daniel M. Harris, and James B. Zagel. With him on the briefs on the original argument were Messrs. Fahner and Harris.

Solicitor General Lee argued the cause on reargument for the United States as amicus curiae urging reversal. With him on the brief on reargument were Assistant Attorney General Jensen, Deputy Solicitor General Frey, Kathryn A. Oberly, Geoffrey S. Stewart, and Robert J. Erickson. With him on the brief on the original argument were Mr. Jensen, Alan I. Horowitz, and David B. Smith.

James W. Reilley reargued the cause for respondents. With him on the brief on reargument were Barry E. Witlin and Thomas Y. Davies. With him on the brief on the original argument were Mr. Witlin, Allan A. Ackerman, and Clyde W. Woody.*

[Footnote *] Briefs of amici curiae urging reversal were filed by George Deukmejian, Attorney General, Robert H. Philibosian, Chief Assistant Attorney General, William D. Stein, Assistant Attorney General, and Clifford K. Thompson, Jr., Deputy Attorney General, for the State of California; by Fred E. Inbau, Wayne W. Schmidt, James P. Manak, Patrick F. Healy, William K. Lambie, and James A. Murphy for Americans for Effective Law Enforcement, Inc., et al.; by Robert L. Toms, Evelle J. Younger, [462 U.S. 213, 216] G. Joseph Bertain, Jr., and Lloyd F. Dunn for Laws at Work et al.; and by Newman A. Flanagan, Jack E. Yelverton, James P. Manak, Edwin L. Miller, Jr., Austin J. McGuigan, and John M. Massameno for the National District Attorneys Association, Inc.

Briefs of amici curiae urging affirmance were filed by Sidney Bernstein and Howard A. Specter for the Association of Trial Lawyers of America; by John C. Feirich, Melvin B. Lewis, Joshua Sachs, and Michael J. Costello for the Illinois State Bar Association; by Herman Kaufman and Edward M. Chikofsky for the New York Criminal Bar Association; and by James M. Doyle for the Legal Internship Program, Georgetown University Law Center.

Briefs of amici curiae were filed by Jim Smith, attorney General, and Lawrence A. Kaden and Raymond L. Marky, Assistant Attorneys General, for the State of Florida et al.; by Gerald Baliles, Attorney General, and Jacqueline G. Epps, Senior Assistant Attorney General, for the Commonwealth of Virginia; by Morris Harrell, William W. Greenhalgh, William J. Mertens, and Steven H. Goldblatt for the American Bar Association; by Charles S. Sims and Burt Neuborne for the American Civil Liberties Union et al.; by Peter L. Zimroth and Barbara D. Underwood for the Committee on Criminal Law of the Association of the Bar of the City of New York; by Marshall W. Krause, Quin Denvir, Steffan B. Imhoff, and Paul Edward Bell for the National Association of Criminal Defense Lawyers et al.; by Kenneth M. Mogill for the National Legal Aid and Defender Association; by Frank G. Carrington, Jr., Griffin B. Bell, Wayne W. Schmidt, Alan Dye, Thomas Hendrickson, Courtney A. Evans, Rufus L. Edmisten, David S. Crump, Howard A. Kramer, Ronald A. Zumbrun, John H. Findley, Wayne T. Elliott, G. Stephen Parker, and Joseph E. Scuro for Seven Former Members of the Attorney General of the United States' Task Force on Violent Crime (1981) et al.; and by Dan Johnston, pro se, for the County Attorney of Polk County, Iowa. [462 U.S. 213, 216]

JUSTICE REHNQUIST delivered the opinion of the Court.

Respondents Lance and Susan Gates were indicted for violation of state drug laws after police officers, executing a search warrant, discovered marihuana and other contraband in their automobile and home. Prior to trial the Gateses moved to suppress evidence seized during this search. The Illinois Supreme Court affirmed the decisions of lower state courts granting the motion. 85 Ill. 2d 376, 423 N. E. 2d 887 (1981). It held that the affidavit submitted in support of the State's application for a warrant to search the Gateses' property [462 U.S. 213, 217] was inadequate under this Court's decisions in Aguilar v. Texas, 378 U.S. 108 (1964), and Spinelli v. United States, 393 U.S. 410 (1969).

I

Our certiorari jurisdiction over decisions from state courts derives from 28 U.S.C. 1257, which provides that "[f]inal judgments or decrees rendered by the highest court of a State in which a decision could be had, may be reviewed by the Supreme Court as follows: . . . (3) By writ of certiorari, . . . where any title, right, privilege or immunity is specially set up or claimed under the constitution, treaties or statutes [462 U.S. 213, 218] of . . . the United States." The provision derives, albeit with important alterations, see, e. g., Act of Dec. 23, 1914, ch. 2, 38 Stat. 790; Act of June 25, 1948, 1257, 62 Stat. 929, from the Judiciary Act of 1789, 25, 1 Stat. 85.

Although we have spoken frequently on the meaning of 1257 and its predecessors, our decisions are in some respects not entirely clear. We held early on that 25 of the Judiciary Act of 1789 furnished us with no jurisdiction unless a federal question had been both raised and decided in the state court below. As Justice Story wrote in Crowell v. Randell, 10 Pet. 368, 392 (1836); "If both of these requirements do not appear on the record, the appellate jurisdiction fails." See also Owings v. Norwood's Lessee, 5 Cranch 344 (1809).1

Notwithstanding these decisions, however, several of our more recent cases have treated the so-called "not pressed or passed upon below" rule as merely a prudential restriction. In Terminiello v. Chicago, 337 U.S. 1 (1949), the Court reversed a state criminal conviction on a ground not urged in state court, nor even in this Court. Likewise, in Vachon v. New Hampshire, 414 U.S. 478 (1974), the Court summarily reversed a state criminal conviction on the ground, not raised in state court, or here, that it had been obtained in violation of the Due Process Clause of the Fourteenth Amendment. The Court indicated in a footnote, id., at 479, n. 3, that it possessed discretion to ignore the failure to raise in state court the question on which it decided the case.

In addition to this lack of clarity as to the character of the "not pressed or passed upon below" rule, we have recognized that it often may be unclear whether the particular federal question presented in this Court was raised or passed upon below. In Dewey v. Des Moines, 173 U.S. 193, 197-198 (1899), the fullest treatment of the subject, the Court said [462 U.S. 213, 220] that "[i]f the question were only an enlargement of the one mentioned in the assignment of errors, or if it were so connected with it in substance as to form but another ground or reason for alleging the invalidity of the [lower court's] judgment, we should have no hesitation in holding the assignment sufficient to permit the question to be now raised and argued. Parties are not confined here to the same arguments which were advanced in the courts below upon a Federal question there discussed."2 We have not attempted, and likely would not have been able, to draw a clear-cut line between cases involving only an "enlargement" of questions presented below and those involving entirely new questions.

The application of these principles in the instant case is not entirely straightforward. It is clear in this case that respondents expressly raised, at every level of the Illinois judicial system, the claim that the Fourth Amendment had been violated by the actions of the Illinois police and that the evidence seized by the officers should be excluded from their trial. It also is clear that the State challenged, at every level of the Illinois court system, respondents' claim that the substantive requirements of the Fourth Amendment had been violated. The State never, however, raised or addressed the question whether the federal exclusionary rule should be modified in any respect, and none of the opinions of the [462 U.S. 213, 221] Illinois courts give any indication that the question was considered.

The case, of course, is before us on the State's petition for a writ of certiorari. Since the Act of Dec. 23, 1914, ch. 2, 38 Stat. 790, jurisdiction has been vested in this Court to review state-court decisions even when a claimed federal right has been upheld. Our prior decisions interpreting the "not pressed or passed on below" rule have not, however, involved a State's failure to raise a defense to a federal right or remedy asserted below. As explained below, however, we can see no reason to treat the State's failure to have challenged an asserted federal claim differently from the failure of the proponent of a federal claim to have raised that claim.

We have identified several purposes underlying the "not pressed or passed upon" rule: for the most part, these are as applicable to the State's failure to have opposed the assertion of a particular federal right, as to a party's failure to have asserted the claim. First, "[q]uestions not raised below are those on which the record is very likely to be inadequate since it certainly was not complied with those questions in mind." Cardinale v. Louisiana, 394 U.S. 437, 439 (1969). Exactly the same difficulty exists when the State urges modification of an existing constitutional right or accompanying remedy. Here, for example, the record contains little, if anything, regarding the subjective good faith of the police officers that searched the Gateses' property - which might well be an important consideration in determining whether to fashion a good-faith exception to the exclusionary rule. Our consideration of whether to modify the exclusionary rule plainly would benefit from a record containing such facts.

Likewise, "due regard for the appropriate relationship of this court to state courts," McGoldrick v. Compagnie Generale Transatlantique, 309 U.S., at 434-435, demands that those courts be given an opportunity to consider the constitutionality of the actions of state officials, and, equally important, proposed changes in existing remedies for unconstitutional [462 U.S. 213, 222] actions. Finally, by requiring that the State first argue to the state courts that the federal exclusionary rule should be modified, we permit a state court, even if it agrees with the State as a matter of federal law, to rest its decision on an adequate and independent state ground. See Cardinale, supra, at 439. Illinois, for example, adopted an exclusionary rule as early as 1923, see People v. Brocamp, 307 Ill. 448, 138 N. E. 728 (1923), and might adhere to its view even if it thought we would conclude that the federal rule should be modified. In short, the reasons supporting our refusal to hear federal claims not raised in state court apply with equal force to the State's failure to challenge the availability of a well-settled federal remedy. Whether the "not pressed or passed upon below" rule is jurisdictional, as our earlier decisions indicate, see supra, at 217-219, or prudential, as several of our later decisions assume, or whether its character might be different in cases like this from its character elsewhere, we need not decide. Whatever the character of the rule may be, consideration of the question presented in our order of November 29, 1982, would be contrary to the sound justifications for the "not pressed or passed upon below" rule, and we thus decide not to pass on the issue.

The fact that the Illinois courts affirmatively applied the federal exclusionary rule - suppressing evidence against respondents - does not affect our conclusion. In Morrison v. Watson, 154 U.S. 111 (1894), the Court was asked to consider whether a state statute impaired the plaintiff in error's contract with the defendant in error. It declined to hear the case because the question presented here had not been pressed or passed on below. The Court acknowledged that the lower court's opinion had restated the conclusion, set forth in an earlier decision of that court, that the state statute did not impermissibly impair contractual obligations. Nonetheless, it held that there was no showing that "there was any real contest at any stage of this case upon the point," id., at 115, and that without such a contest, the routine restatement [462 U.S. 213, 223] and application of settled law by an appellate court did not satisfy the "not pressed or passed upon below" rule. Similarly, in the present case, although the Illinois courts applied the federal exclusionary rule, there was never "any real contest" upon the point. The application of the exclusionary rule was merely a routine act, once a violation of the Fourth Amendment had been found, and not the considered judgment of the Illinois courts on the question whether application of a modified rule would be warranted on the facts of this case. In such circumstances, absent the adversarial dispute necessary to apprise the state court of the arguments for not applying the exclusionary rule, we will not consider the question whether the exclusionary rule should be modified.

Likewise, we do not believe that the State's repeated opposition to respondents' substantive Fourth Amendment claims suffices to have raised the question whether the exclusionary rule should be modified. The exclusionary rule is "a judicially created remedy designed to safeguard Fourth Amendment rights generally" and not "a personal constitutional right of the party aggrieved." United States v. Calandra, 414 U.S. 338, 348 (1974). The question whether the exclusionary rule's remedy is appropriate in a particular context has long been regarded as an issue separate from the question whether the Fourth Amendment rights of the party seeking to invoke the rule were violated by police conduct. See, e. g., United States v. Havens, 446 U.S. 620 (1980); United States v. Ceccolini, 435 U.S. 268 (1978); United States v. Calandra, supra; Stone v. Powell, 428 U.S. 465 (1976). Because of this distinction, we cannot say that modification or abolition of the exclusionary rule is "so connected with [the substantive Fourth Amendment right at issue] as to form but another ground or reason for alleging the invalidity" of the judgment. Dewey v. Des Moines, 173 U.S., at 197-198. Rather, the rule's modification was, for purposes of the "not pressed or passed upon below" rule, a separate claim that had to be specifically presented to the state courts. [462 U.S. 213, 224]

Finally, weighty prudential considerations militate against our considering the question presented in our order of November 29, 1982. The extent of the continued vitality of the rules that have developed from our decisions in Weeks v. United States, 232 U.S. 383 (1914), and Mapp v. Ohio, 367 U.S. 643 (1961), is an issue of unusual significance. Sufficient evidence of this lies just in the comments on the issue that Members of this Court recently have made, e. g., Bivens v. Six Unknown Fed. Narcotics Agents, 403 U.S. 388, 415 (1971) (BURGER, C. J., dissenting); Coolidge v. New Hampshire, 403 U.S. 443, 490 (1971) (Harlan, J., concurring); id., at 502 (Black, J., dissenting); Stone v. Powell, supra, at 537-539 (WHITE, J., dissenting); Brewer v. Williams, 430 U.S. 387, 413-414 (1977) (POWELL, J., concurring); Robbins v. California, 453 U.S. 420, 437, 443-444 (1981) (REHNQUIST, J., dissenting). Where difficult issues of great public importance are involved, there are strong reasons to adhere scrupulously to the customary limitations on our discretion. By doing so we "promote respect . . . for the Court's adjudicatory process [and] the stability of [our] decisions." Mapp v. Ohio, 367 U.S., at 677 (Harlan, J., dissenting). Moreover, fidelity to the rule guarantees that a factual record will be available to us, thereby discouraging the framing of broad rules, seemingly sensible on one set of facts, which may prove ill-considered in other circumstances. In Justice Harlan's words, adherence to the rule lessens the threat of "untoward practical ramifications," id., at 676 (dissenting opinion), not foreseen at the time of decision. The public importance of our decisions in Weeks and Mapp and the emotions engendered by the debate surrounding these decisions counsel that we meticulously observe our customary procedural rules. By following this course, we promote respect for the procedures by which our decisions are rendered, as well as confidence in the stability of prior decisions. A wise exercise of the powers confided in this Court dictates that we reserve for another day the question whether the exclusionary rule should be modified. [462 U.S. 213, 225]

II

Mader then made arrangements with an agent of the Drug Enforcement Administration for surveillance of the May 5 Eastern Airlines flight. The agent later reported to Mader that Gates had boarded the flight, and that federal agents in Florida had observed him arrive in West Palm Beach and take a taxi to the nearby Holiday Inn. They also reported that Gates went to a room registered to one Susan Gates and that, at 7 o'clock the next morning, Gates and an unidentified woman left the motel in a Mercury bearing Illinois license plates and drove northbound on an interstate highway frequently used by travelers to the Chicago area. In addition, the DEA agent informed Mader that the license plate number on the Mercury was registered to a Hornet station wagon owned by Gates. The agent also advised Mader that the driving time between West Palm Beach and Bloomingdale was approximately 22 to 24 hours.

Mader signed an affidavit setting forth the foregoing facts, and submitted it to a judge of the Circuit Court of Du Page County, together with a copy of the anonymous letter. The judge of that court thereupon issued a search warrant for the Gateses' residence and for their automobile. The judge, in deciding to issue the warrant, could have determined that the modus operandi of the Gateses had been substantially corroborated. As the anonymous letter predicted, Lance Gates had flown from Chicago to West Palm Beach late in the afternoon of May 5th, had checked into a hotel room registered in the name of his wife, and, at 7 o'clock the following morning, had headed north, accompanied by an unidentified woman, [462 U.S. 213, 227] out of West Palm Beach on an interstate highway used by travelers from South Florida to Chicago in an automobile bearing a license plate issued to him.

At 5:15 a. m. on March 7, only 36 hours after he had flown out of Chicago, Lance Gates, and his wife, returned to their home in Bloomingdale, driving the car in which they had left West Palm Beach some 22 hours earlier. The Bloomingdale police were awaiting them, searched the truck of the Mercury, and uncovered approximately 350 pounds of marihuana. A search of the Gateses' home revealed marihuana, weapons, and other contraband. The Illinois Circuit court ordered suppression of all these items, on the ground that the affidavit submitted to the Circuit Judge failed to support the necessary determination of probable cause to believe that the Gateses' automobile and home contained the contraband in question. This decision was affirmed in turn by the Illinois Appellate Court, 82 Ill. App. 3d 749, 403 N. E. 2d 77 (1980), and by a divided vote of the Supreme court of Illinois. 85 Ill. 2d 376, 423 N. E. 2d 887 (1981).

The Illinois Supreme Court concluded - and we are inclined to agree - that, standing alone, the anonymous letter sent to the Bloomingdale Police Department would not provide the basis for a magistrate's determination that there was probable cause to believe contraband would be found in the Gateses' car and home. The letter provides virtually nothing from which one might conclude that its author is either honest or his information reliable; likewise, the letter gives absolutely no indication of the basis for the writer's predictions regarding the Gateses' criminal activities. Something more was required, then, before a magistrate could conclude that there was probable cause to believe that contraband would be found in the Gateses' home and car. See Aguilar v. Texas, 378 U.S., at 109, n. 1; Nathanson v. United States, 290 U.S. 41 (1933).

The Illinois Supreme Court also properly recognized that Detective Mader's affidavit might be capable of supplementing [462 U.S. 213, 228] the anonymous letter with information sufficient to permit a determination of probable cause. See Whiteley v. Warden, 401 U.S. 560, 567 (1971). In holding that the affidavit in fact did not contain sufficient additional information to sustain a determination of probable cause, the Illinois court applied a "two-pronged test," derived from our decision in Spinelli v. United States, 393 U.S. 410 (1969).3 The Illinois Supreme Court, like some others, apparently understood Spinelli as requiring that the anonymous letter satisfy each of two independent requirements before it could be relied on. 85 Ill. 2d, at 383, 423 N. E. 2d, at 890. According to this view, the letter, as supplemented by Mader's affidavit, first had to adequately reveal the "basis of knowledge" of the letterwriter - the particular means by which he came by the information given in his report. Second, it had to provide [462 U.S. 213, 229] facts sufficiently establishing either the "veracity" of the affiant's informant, or, alternatively, the "reliability" of the informant's report in this particular case.

The Illinois court, alluding to an elaborate set of legal rules that have developed among various lower courts to enforce the "two-pronged test,"4 found that the test had not been satisfied. First, the "veracity" prong was not satisfied because, "[t]here was simply no basis [for] conclud[ing] that the anonymous person [who wrote the letter to the Bloomingdale Police Department] was credible." Id., at 385, 423 N. E. 2d, at 891. The court indicated that corroboration by police of details contained in the letter might never satisfy the "veracity" prong, and in any event, could not do so if, as in the present case, only "innocent" details are corroborated. Id., at 390, 423 N. E. 2d, at 893. In addition, the letter gave no indication of the basis of its writer's knowledge of the [462 U.S. 213, 230] Gateses' activities. The Illinois court understood Spinelli as permitting the detail contained in a tip to be used to infer that the informant had a reliable basis for his statements, but it thought that the anonymous letter failed to provide sufficient detail to permit such an inference. Thus, it concluded that no showing of probable cause had been made.

We agree with the Illinois Supreme Court that an informant's "veracity," "reliability," and "basis of knowledge" are all highly relevant in determining the value of his report. We do not agree, however, that these elements should be understood as entirely separate and independent requirements to be rigidly exacted in every case,5 which the opinion of the Supreme Court of Illinois would imply. Rather, as detailed below, they should be understood simply as closely intertwined issues that may usefully illuminate the common-sense, practical question whether there is "probable cause" to believe that contraband or evidence is located in a particular place.

III

Moreover, the "two-pronged test" directs analysis into two largely independent channels - the informant's "veracity' or "reliability" and his "basis of knowledge." See nn. 4 and 5, supra. There are persuasive arguments against according these two elements such independent status. Instead, they are better understood as relevant considerations in the totality-of-the-circumstances analysis that traditionally has guided probable-cause determinations: a deficiency in one may be compensated for, in determining the overall reliability of a tip, by a strong showing as to the other, or by some other indicia of reliability. See, e. g., Adams v. Williams, supra, at 146-147; United States v. Harris, 403 U.S. 573 (1971).

If, for example, a particular informant is known for the unusual reliability of his predictions of certain types of criminal activities in a locality, his failure, in a particular case, to thoroughly set forth the basis of his knowledge surely should not serve as an absolute bar to a finding of probable cause based on his tip. See United States v. Sellers, 483 F.2d 37 (CA5 1973).8 Likewise, if an unquestionably honest citizen comes forward with a report of criminal activity - which if fabricated would subject him to criminal liability - we have found [462 U.S. 213, 234] rigorous scrutiny of the basis of his knowledge unnecessary. Adams v. Williams, supra. Conversely, even if we entertain some doubt as to an informant's motives, his explicit and detailed description of alleged wrongdoing, along with a statement that the event was observed firsthand, entitles his tip to greater weight than might otherwise be the case. Unlike a totality-of-the-circumstances analysis, which permits a balanced assessment of the relative weights of all the various indicia of reliability (and unreliability) attending an informant's tip, the "two-pronged test" has encouraged an excessively technical dissection of informants' tips,9 with undue attention [462 U.S. 213, 235] being focused on isolated issues that cannot sensibly be divorced from the other facts presented to the magistrate.

As early as Locke v. United States, 7 Cranch 339, 348 (1813), Chief Justice Marshall observed, in a closely related context: "[T]he term `probable cause,' according to its usual acceptation, means less than evidence which would justify condemnation . . . . It imports a seizure made under circumstances which warrant suspicion." More recently, we said that "the quanta . . . of proof" appropriate in ordinary judicial proceedings are inapplicable to the decision to issue a warrant. Brinegar, 338 U.S., at 173. Finely tuned standards such as proof beyond a reasonable doubt or by a preponderance of the evidence, useful in formal trials, have no place in the magistrate's decision. While an effort to fix some general, numerically precise degree of certainty corresponding to "probable cause" may not be helpful, it is clear that "only the probability, and not a prima facie showing, of criminal activity is the standard of probable cause." Spinelli, 393 U.S., at 419. See Model Code of Pre-Arraignment Procedure 210.1(7) (Prop. Off. Draft 1972); 1 W. LaFave, Search and Seizure 3.2(e) (1978).

We also have recognized that affidavits "are normally drafted by nonlawyers in the midst and haste of a criminal investigation. Technical requirements of elaborate specificity once enacted under common law pleadings have no proper place in this area." United States v. Ventresca, 380 U.S. 102, 108 (1965). Likewise, search and arrest warrants long have been issued by persons who are neither lawyers nor judges, and who certainly do not remain abreast of each judicial refinement of the nature of "probable cause." See Shadwick v. City of Tampa, 407 U.S. 345, 348-350 (1972). The rigorous inquiry into the Spinelli prongs and the complex superstructure of evidentiary and analytical rules that some have seen implicit in our Spinelli decision, cannot be reconciled with the fact that many warrants are - quite properly, 407 U.S., at 348-350 - issued on the basis of nontechnical, [462 U.S. 213, 236] common-sense judgments of laymen applying a standard less demanding than those used in more formal legal proceedings. Likewise, given the informal, often hurried context in which it must be applied, the "built-in subtleties," Stanley v. State, 19 Md. App. 507, 528, 313 A. 2d 847, 860 (1974), of the "two-pronged test" are particularly unlikely to assist magistrates in determining probable cause.

Similarly, we have repeatedly said that after-the-fact scrutiny by courts of the sufficiency of an affidavit should not take the form of de novo review. A magistrate's "determination of probable cause should be paid great deference by reviewing courts." Spinelli, supra, at 419. "A grudging or negative attitude by reviewing courts toward warrants," Ventresca, 380 U.S., at 108, is inconsistent with the Fourth Amendment's strong preference for searches conducted pursuant to a warrant; "courts should not invalidate warrant[s] by interpreting affidavit[s] in a hypertechnical, rather than a commonsense, manner." Id., at 109.

If the affidavits submitted by police officers are subjected to the type of scrutiny some courts have deemed appropriate, police might well resort to warrantless searches, with the hope of relying on consent or some other exception to the Warrant Clause that might develop at the time of the search. In addition, the possession of a warrant by officers conducting an arrest or search greatly reduces the perception of unlawful or intrusive police conduct, by assuring "the individual whose property is searched or seized of the lawful authority of the executing officer, his need to search, and the limits of his power to search." United States v. Chadwick, 433 U.S. 1, 9 (1977). Reflecting this preference for the warrant process, the traditional standard for review of an issuing magistrate's probable-cause determination has been that so long as the magistrate had a "substantial basis for . . . conclud[ing]" that a search would uncover evidence of wrongdoing, the Fourth Amendment requires no more. Jones v. United States, 362 U.S. 257, 271 (1960). See United States v. [462 U.S. 213, 237] Harris, 403 U.S., at 577-583.10 We think reaffirmation of this standard better serves the purpose of encouraging recourse to the warrant procedure and is more consistent with our traditional deference to the probable-cause determinations of magistrates than is the "two-pronged test."

Finally, the direction taken by decisions following Spinelli poorly serves "[t]he most basic function of any government": "to provide for the security of the individual and of his property." Miranda v. Arizona, 384 U.S. 436, 539 (1966) (WHITE, J., dissenting). The strictures that inevitably accompany the "two-pronged test" cannot avoid seriously impeding the task of law enforcement, see, e. g., n. 9, supra. If, as the Illinois Supreme Court apparently thought, that test must be rigorously applied in every case, anonymous tips would be of greatly diminished value in police work. Ordinary citizens, like ordinary witnesses, see Advisory Committee's Notes on Fed. Rule Evid. 701, 28 U.S.C. App., p. 570, generally do not provide extensive recitations of the basis of their everyday observations. Likewise, as the Illinois Supreme Court observed in this case, the veracity of persons supplying anonymous tips is by hypothesis largely unknown, and unknowable. As a result, anonymous tips seldom could survive a rigorous application of either of the Spinelli prongs. Yet, such tips, particularly when supplemented by [462 U.S. 213, 238] independent police investigation, frequently contribute to the solution of otherwise "perfect crimes." While a conscientious assessment of the basis for crediting such tips is required by the Fourth Amendment, a standard that leaves virtually no place for anonymous citizen informants is not.

For all these reasons, we conclude that it is wiser to abandon the "two-pronged test" established by our decisions in Aguilar and Spinelli.11 In its place we reaffirm the totality-of-the-circumstances analysis that traditionally has informed probable-cause determinations. See Jones v. United States, supra; United States v. Ventresca, 380 U.S. 102 (1965); Brinegar v. United States, 338 U.S. 160 (1949). The task of the issuing magistrate is simply to make a practical, common-sense decision whether, given all the circumstances set forth in the affidavit before him, including the "veracity" and "basis of knowledge" of persons supplying hearsay information, there is a fair probability that contraband or evidence of a crime will be found in a particular place. And the duty of a reviewing court is simply to ensure that the magistrate had a "substantial basis for . . . conclud[ing]" that probable cause [462 U.S. 213, 239] existed. Jones v. United States, 362 U.S., at 271. We are convinced that this flexible, easily applied standard will better achieve the accommodation of public and private interests that the Fourth Amendment requires than does the approach that has developed from Aguilar and Spinelli.

Our earlier cases illustrate the limits beyond which a magistrate may not venture in issuing a warrant. A sworn statement of an affiant that "he has cause to suspect and does believe" that liquor illegally brought into the United States is located on certain premises will not do. Nathanson v. United States, 290 U.S. 41 (1933). An affidavit must provide the magistrate with a substantial basis for determining the existence of probable cause, and the wholly conclusory statement at issue in Nathanson failed to meet this requirement. An officer's statement that "[a]ffiants have received reliable information from a credible person and do believe" that heroin is stored in a home, is likewise inadequate. Aguilar v. Texas, 378 U.S. 108 (1964). As in Nathanson, this is a mere conclusory statement that gives the magistrate virtually no basis at all for making a judgment regarding probable cause. Sufficient information must be presented to the magistrate to allow that official to determine probable cause; his action cannot be a mere ratification of the bare conclusions of others. In order to ensure that such an abdication of the magistrate's duty does not occur, courts must continue to conscientiously review the sufficiency of affidavits on which warrants are issued. But when we move beyond the "bare bones" affidavits present in cases such as Nathanson and Aguilar, this area simply does not lend itself to a prescribed set of rules, like that which had developed from Spinelli. Instead, the flexible, common-sense standard articulated in Jones, Ventresca, and Brinegar better serves the purposes of the Fourth Amendment's probable-cause requirement.

JUSTICE BRENNAN'S dissent suggests in several places that the approach we take today somehow downgrades the [462 U.S. 213, 240] role of the neutral magistrate, because Aguilar and Spinelli "preserve the role of magistrates as independent arbiters of probable cause . . . ." Post, at 287. Quite the contrary, we believe, is the case. The essential protection of the warrant requirement of the Fourth Amendment, as stated in Johnson v. United States, 333 U.S. 10 (1948), is in "requiring that [the usual inferences which reasonable men draw from evidence] be drawn by a neutral and detached magistrate instead of being judged by the officer engaged in the often competitive enterprise of ferreting out crime." Id., at 13-14. Nothing in our opinion in any way lessens the authority of the magistrate to draw such reasonable inferences as he will from the material supplied to him by applicants for a warrant; indeed, he is freer than under the regime of Aguilar and Spinelli to draw such inferences, or to refuse to draw them if he is so minded.

The real gist of JUSTICE BRENNAN'S criticism seems to be a second argument, somewhat at odds with the first, that magistrates should be restricted in their authority to make probable-cause determinations by the standards laid down in Aguilar and Spinelli, and that such findings "should not be authorized unless there is some assurance that the information on which they are based has been obtained in a reliable way by an honest or credible person." Post, at 283. However, under our opinion magistrates remain perfectly free to exact such assurances as they deem necessary, as well as those required by this opinion, in making probable-cause determinations. JUSTICE BRENNAN would apparently prefer that magistrates be restricted in their findings of probable cause by the development of an elaborate body of case law dealing with the "veracity" prong of the Spinelli test, which in turn is broken down into two "spurs" - the informant's "credibility" and the "reliability" of his information, together with the "basis of knowledge" prong of the Spinelli test. See n. 4, supra. That such a labyrinthine body of judicial refinement bears any relationship to familiar definitions of [462 U.S. 213, 241] probable cause is hard to imagine. As previously noted, probable cause deals "with probabilities. These are not technical; they are the factual and practical considerations of everyday life on which reasonable and prudent men, not legal technicians, act," Brinegar v. United States, 338 U.S., at 175.

JUSTICE BRENNAN'S dissent also suggests that "[w]ords such as `practical,' `nontechnical,' and `common sense,' as used in the Court's opinion, are but code words for an overly permissive attitude towards police practices in derogation of the rights secured by the Fourth Amendment." Post, at 290. An easy, but not a complete, answer to this rather florid statement would be that nothing we know about Justice Rutledge suggests that he would have used the words he chose in Brinegar in such a manner. More fundamentally, no one doubts that "under our Constitution only measures consistent with the Fourth Amendment may be employed by government to cure [the horrors of drug trafficking]," post, at 290; but this agreement does not advance the inquiry as to which measures are, and which measures are not, consistent with the Fourth Amendment. "Fidelity" to the commands of the Constitution suggests balanced judgment rather than exhortation. The highest "fidelity" is not achieved by the judge who instinctively goes furthest in upholding even the most bizarre claim of individual constitutional rights, any more than it is achieved by a judge who instinctively goes furthest in accepting the most restrictive claims of governmental authorities. The task of this Court, as of other courts, is to "hold the balance true," and we think we have done that in this case.

IV

Our decisions applying the totality-of-the-circumstances analysis outlined above have consistently recognized the value of corroboration of details of an informant's tip by independent police work. In Jones v. United States, 362 U.S., at 269, we held that an affidavit relying on hearsay "is not to [462 U.S. 213, 242] be deemed insufficient on that score, so long as a substantial basis for crediting the hearsay is presented." We went on to say that even in making a warrantless arrest an officer "may rely upon information received through an informant, rather than upon his direct observations, so long as the informant's statement is reasonably corroborated by other matters within the officer's knowledge." Ibid. Likewise, we recognized the probative value of corroborative efforts of police officials in Aguilar - the source of the "two-pronged test" - by observing that if the police had made some effort to corroborate the informant's report at issue, "an entirely different case" would have been presented. Aguilar, 378 U.S., at 109, n. 1.

Our decision in Draper v. United States, 358 U.S. 307 (1959), however, is the classic case on the value of corroborative efforts of police officials. There, an informant named Hereford reported that Draper would arrive in Denver on a train from Chicago on one of two days, and that he would be carrying a quantity of heroin. The informant also supplied a fairly detailed physical description of Draper, and predicted that he would be wearing a light colored raincoat, brown slacks, and black shoes, and would be walking "real fast." Id., at 309. Hereford gave no indication of the basis for his information.12

On one of the stated dates police officers observed a man matching this description exit a train arriving from Chicago; his attire and luggage matched Hereford's report and he was [462 U.S. 213, 243] walking rapidly. We explained in Draper that, by this point in his investigation, the arresting officer "had personally verified every facet of the information given him by Hereford except whether petitioner had accomplished his mission and had the three ounces of heroin on his person or in his bag. And surely, with every other bit of Hereford's information being thus personally verified, [the officer] had `reasonable grounds' to believe that the remaining unverified bit of Hereford's information - that Draper would have the heroin with him - was likewise true," id., at 313.

The showing of probable cause in the present case was fully as compelling as that in Draper. Even standing alone, the facts obtained through the independent investigation of Mader and the DEA at least suggested that the Gateses were involved in drug trafficking. In addition to being a popular vacation site, Florida is well known as a source of narcotics and other illegal drugs. See United States v. Mendenhall, 446 U.S. 544, 562 (1980) (POWELL, J., concurring in part and concurring in judgment); DEA, Narcotics Intelligence Estimate, The Supply of Drugs to the U.S. Illicit Market From Foreign and Domestic Sources in 1980, pp. 8-9. Lance Gates' flight to West Palm Beach, his brief, overnight stay in a motel, and apparent immediate return north to Chicago in the family car, conveniently awaiting him in West Palm Beach, is as suggestive of a prearranged drug run, as it is of an ordinary vacation trip.

In addition, the judge could rely on the anonymous letter, which had been corroborated in major part by Mader's efforts - just as had occurred in Draper.13 The Supreme Court [462 U.S. 213, 244] of Illinois reasoned that Draper involved an informant who had given reliable information on previous occasions, while the honesty and reliability of the anonymous informant in this case were unknown to the Bloomingdale police. While this distinction might be an apt one at the time the Police Department received the anonymous letter, it became far less significant after Mader's independent investigative work occurred. The corroboration of the letter's predictions that the Gateses' car would be in Florida, that Lance Gates would fly to Florida in the next day or so, and that he would drive the car north toward Bloomingdale all indicated, albeit not with certainty, that the informant's other assertions also were true. "[B]ecause an informant is right about some things, he is more probably right about other facts," Spinelli, 393 U.S., at 427 (WHITE, J., concurring) - including the claim regarding the Gateses' illegal activity. This may well not be the type of "reliability" or "veracity" necessary to satisfy some views of the "veracity prong" of Spinelli, but we think it suffices for the practical, common-sense judgment called for in making a probable-cause determination. It is enough, for purposes of assessing probable cause, that "[c]orroboration through other sources of information reduced the [462 U.S. 213, 245] chances of a reckless or prevaricating tale," thus providing "a substantial basis for crediting the hearsay." Jones v. United States, 362 U.S., at 269, 271.

[Footnote 1] The apparent rule of Crowell v. Randell that a federal claim have been both raised and addressed in state court was generally not understood in the literal fashion in which it was phrased. See R. Robertson & F. Kirkham, Jurisdiction of the Supreme Court of the United States 60 (1951). Instead, the Court developed the rule that a claim would not be considered here unless it had been either raised or squarely considered and resolved in state court. See, e. g., McGoldrick v. Compagnie Generale Transatlantique, 309 U.S. 430, 434-435 (1940); State Farm Mutual Ins. Co. v. Duel, 324 U.S. 154, 160 (1945).

[Footnote 2] In Dewey, certain assessments had been levied against the owner of property abutting a street paved by the city; a state trial court ordered that the property be forfeited when the assessments were not paid, and in addition, held the plaintiff in error personally liable for the amount by which the assessments exceeded the value of the lots. In state court the plaintiff in error argued that the imposition of personal liability against him violated the Due Process Clause of the Fourteenth Amendment, because he had not received personal notice of the assessment proceedings. In this Court, he also attempted to argue that the assessment itself constituted a taking under the Fourteenth Amendment. The Court held that, beyond arising from a single factual occurrence, the two claims "are not in anywise necessarily connected," 173 U.S., at 198. Because of this, we concluded that the plaintiff in error's taking claim could not be considered.

[Footnote 3] In Spinelli, police officers observed Mr. Spinelli going to and from a particular apartment, which the telephone company said contained two telephone with stated numbers. The officers also were "informed by a confidential reliable informant that William Spinelli [was engaging in illegal gambling activities]" at the apartment, and that he used two phones, with numbers corresponding to those possessed by the police. 393 U.S., at 414. The officers submitted an affidavit with this information to a magistrate and obtained a warrant to search Spinelli's apartment. We held that the magistrate could have made his determination of probable cause only by "abdicating his constitutional function," id., at 416. The Government's affidavit contained absolutely no information regarding the informant's reliability. Thus, it did not satisfy Aguilar's requirement that such affidavits contain "some of the underlying circumstances" indicating that "the informant . . . was `credible'" or that "his information [was] `reliable.'" Aguilar v. Texas, 378 U.S. 108, 114 (1964). In addition, the tip failed to satisfy Aguilar's requirement that it detail "some of the underlying circumstances from which the informant concluded that . . . narcotics were where he claimed they were." Ibid. We also held that if the tip concerning Spinelli had contained "sufficient detail" to permit the magistrate to conclude "that he [was] relying on something more substantial than a casual rumor circulating in the underworld or an accusation based merely on an individual's general reputation," 393 U.S., at 416, then he properly could have relied on it; we thought, however, that the tip lacked the requisite detail to permit this "self-verifying detail" analysis.

[Footnote 4] See, e. g., Stanley v. State, 19 Md. App. 507, 313 A. 2d 847 (1974). In summary, these rules posit that the "veracity" prong of the Spinelli test has two "spurs" - the informant's "credibility" and the "reliability" of his information. Various interpretations are advanced for the meaning of the "reliability" spur of the "veracity" prong. Both the "basis of knowledge" prong and the "veracity" prong are treated as entirely separate requirements, which must be independently satisfied in every case in order to sustain a determination of probable cause. See n. 5, infra. Some ancillary doctrines are relied on to satisfy certain of the foregoing requirements. For example, the "self-verifying detail" of a tip may satisfy the "basis of knowledge" requirement, although not the "credibility" spur of the "veracity" prong. See 85 Ill. 2d, at 388, 423 N. E. 2d, at 892. Conversely, corroboration would seem not capable of supporting the "basis of knowledge" prong, but only the "veracity" prong. Id., at 390, 423 N. E. 2d, at 893.

The decision in Stanley, while expressly approving and conscientiously attempting to apply the "two-pronged test" observes that "[t]he built-in subtleties [of the test] are such, however, that a slipshod application calls down upon us the fury of Murphy's Law." 19 Md. App., at 528, 313 A. 2d, at 860 (footnote omitted). The decision also suggested that it is necessary to "evolve analogous guidelines [to hearsay rules employed in trial settings] for the reception of hearsay in a probable cause setting." Id., at 522, n. 12, 313 A. 2d, at 857, n. 12.

[Footnote 5] The entirely independent character that the Spinelli prongs have assumed is indicated both by the opinion of the Illinois Supreme Court in this case, and by decisions of other courts. One frequently cited decision, Stanley v. State, supra, at 530, 313 A. 2d, at 861 (footnote omitted), remarks that "the dual requirements represented by the `two-pronged test' are `analytically severable' and an `overkill' on one prong will not carry over to make up for a deficit on the other prong." See also n. 9, infra.

Likewise, in Rugendorf v. United States, 376 U.S. 528 (1964), the Court upheld a magistrate's determination that there was probable cause to believe that certain stolen property would be found in petitioner's apartment. The affidavit submitted to the magistrate stated that certain furs had been stolen, and that a confidential informant, who previously had furnished confidential information, said that the saw the furs in petitioner's home. Moreover, another confidential informant, also claimed to be reliable, stated that one Schweihs had stolen the furs. Police reports indicated that petitioner had been seen in Schweihs' company, and a third informant stated that petitioner was a fence for Schweihs.

Finally, in Ker v. California, 374 U.S. 23 (1963), we held that information within the knowledge of officers who searched the Kers' apartment provided them with probable cause to believe drugs would be found there. The officers were aware that one Murphy had previously sold marihuana [462 U.S. 213, 233] to a police officer; the transaction had occurred in an isolated area, to which Murphy had led the police. The night after this transaction, police observed Mr. Ker and Murphy meet in the same location. Murphy approached Ker's car, and, although police could see nothing change hands, Murphy's modus operandi was identical to what it had been the night before. Moreover, when police followed Ker from the scene of the meeting with Murphy he managed to lose them after performing an abrupt U-turn. Finally, the police had a statement from an informant who had provided reliable information previously, that Ker was engaged in selling marihuana, and that his source was Murphy. We concluded that "[t]o say that this coincidence of information was sufficient to support a reasonable belief of the officers that Ker was illegally in possession of marijuana is to indulge in understatement." Id., at 36.

[Footnote 8] Compare Stanley v. State, 19 Md. App., at 530, 313 A. 2d, at 861, reasoning that "[e]ven assuming `credibility' amounting to sainthood, the judge still may not accept the bare conclusion . . . of a sworn and known and trusted police-affiant."

[Footnote 9] Some lower court decisions, brought to our attention by the State, reflect a rigid application of such rules. In Bridger v. State, 503 S. W. 2d 801 (Tex. Crim. App. 1974), the affiant had received a confession of armed robbery from one of two suspects in the robbery; in addition, the suspect had given the officer $800 in cash stolen during the robbery. The suspect also told the officer that the gun used in the robbery was hidden in the other suspect's apartment. A warrant issued on the basis of this was invalidated on the ground that the affidavit did not satisfactorily describe how the accomplice had obtained his information regarding the gun.

Likewise, in People v. Palanza, 55 Ill. App. 3d 1028, 371 N. E. 2d 687 (1978), the affidavit submitted in support of an application for a search warrant stated that an informant of proven and uncontested reliability had seen, in specifically described premises, "a quantity of a white crystalline substance which was represented to the informant by a white male occupant of the premises to be cocaine. Informant has observed cocaine on numerous occasions in the past and is thoroughly familiar with its appearance. The informant states that the white crystalline powder he observed in the above described premises appeared to him to be cocaine." Id., at 1029, 371 N. E. 2d, at 688. The warrant issued on the basis of the affidavit was invalidated because "[t]here is no indication as to how the informant or for that matter any other person could tell whether a white substance was cocaine and not some other substance such as sugar or salt." Id., at 1030, 371 N. E. 2d, at 689.

Finally, in People v. Brethauer, 174 Colo. 29, 482 P.2d 369 (1971), an informant, stated to have supplied reliable information in the past, claimed that L. S. D. and marihuana were located on certain premises. The informant supplied police with drugs, which were tested by police and confirmed to be illegal substances. The affidavit setting forth these, and other, facts was found defective under both prongs of Spinelli.

[Footnote 10] We also have said that "[a]lthough in a particular case it may not be easy to determine when an affidavit demonstrates the existence of probable cause, the resolution of doubtful or marginal cases in this area should be largely determined by the preference to be accorded to warrants," United States v. Ventresca, 380 U.S. 102, 109 (1965). This reflects both a desire to encourage use of the warrant process by police officers and a recognition that once a warrant has been obtained, intrusion upon interests protected by the Fourth Amendment is less severe than otherwise may be the case. Even if we were to accept the premise that the accurate assessment of probable cause would be furthered by the "two-pronged test," which we do not, these Fourth Amendment policies would require a less rigorous standard than that which appears to have been read into Aguilar and Spinelli.

[Footnote 11] The Court's decision in Spinelli has been the subject of considerable criticism, both by Members of this Court and others. JUSTICE BLACKMUN, concurring in United States v. Harris, 403 U.S. 573, 585-586 (1971), noted his long-held view "that Spinelli . . . was wrongly decided" by this Court. Justice Black similarly would have overruled that decision. Id., at 585. Likewise, a noted commentator has observed that "[t]he Aguilar-Spinelli formulation has provoked apparently ceaseless litigation." 8A J. Moore, Moore's Federal Practice  41.04, p. 41-43 (1982).

Whether the allegations submitted to the magistrate in Spinelli would, under the view we now take, have supported a finding of probable cause, we think it would not be profitable to decide. There are so many variables in the probable-cause equation that one determination will seldom be a useful "precedent" for another. Suffice it to say that while we in no way abandon Spinelli's concern for the trustworthiness of informers and for the principle that it is the magistrate who must ultimately make a finding of probable cause, we reject the rigid categorization suggested by some of its language.

[Footnote 12] The tip in Draper might well not have survived the rigid application of the "two-pronged test" that developed following Spinelli. The only reference to Hereford's reliability was that he had "been engaged as a `special employee' of the Bureau of Narcotics at Denver for about six months, and from time to time gave information to [the police for] small sums of money, and that [the officer] had always found the information given by Hereford to be accurate and reliable." 358 U.S., at 309. Likewise, the tip gave no indication of how Hereford came by his information. At most, the detailed and accurate predictions in the tip indicated that, however Hereford obtained his information, it was reliable.

[Footnote 13] The Illinois Supreme Court thought that the verification of details contained in the anonymous letter in this case amounted only to "[t]he corroboration of innocent activity," 85 Ill. 2d 376, 390, 423 N. E. 2d 887, 893 (1981), and that this was insufficient to support a finding of probable cause. We are inclined to agree, however, with the observation of Justice Moran in his dissenting opinion that "[i]n this case, just as in Draper, seemingly innocent activity became suspicious in light of the initial tip." Id., at 396, [462 U.S. 213, 244] 423 N. E. 2d, at 896. And it bears noting that all of the corroborating detail established in Draper was of entirely innocent activity - a fact later pointed out by the Court in both Jones v. United States, 362 U.S., at 269-270, and Ker v. California, 374 U.S., at 36.

This is perfectly reasonable. As discussed previously, probable cause requires only a probability or substantial chance of criminal activity, not an actual showing of such activity. By hypothesis, therefore, innocent behavior frequently will provide the basis for a showing of probable cause; to require otherwise would be to sub silentio impose a drastically more rigorous definition of probable cause than the security of our citizens' demands. We think the Illinois court attempted a too rigid classification of the types of conduct that may be relied upon in seeking to demonstrate probable cause. See Brown v. Texas, 443 U.S. 47, 52, n. 2 (1979). In making a determination of probable cause the relevant inquiry is not whether particular conduct is "innocent" or "guilty," but the degree of suspicion that attaches to particular types of noncriminal acts.

[Footnote 14] JUSTICE STEVENS' dissent seizes on one inaccuracy in the anonymous informant's letter - its statement that Sue Gates would fly from Florida to Illinois, when in fact she drove - and argues that the probative value of the entire tip was undermined by this allegedly "material mistake." We have never required that informant's used by the police be infallible, and can see no reason to impose such a requirement in this case. Probable cause, particularly when police have obtained a warrant, simply does not require the perfection the dissent finds necessary.

Likewise, there is no force to the dissent's argument that the Gateses' action in leaving their home unguarded undercut the informants claim that drugs were hidden there. Indeed, the line-by-line scrutiny that the dissent applies to the anonymous letter is akin to that which we find inappropriate in reviewing magistrates' decisions. The dissent apparently attributes to the judge who issued the warrant in this case the rather implausible notion that persons dealing in drugs always stay at home, apparently out of fear that to leave might risk intrusion by criminals. If accurate, one could not help sympathizing with the self-imposed isolation of people so situated. In reality, however, it is scarcely likely that the judge ever thought that the anonymous tip "kept one spouse" at home, much less that he relied on the theory advanced by the dissent. The letter simply says that Sue would fly from Florida to Illinois, without indicating whether the Gateses made the bitter choice of leaving the drugs in their house, or those in their car, unguarded. The judge's determination that there might be drugs or evidence of criminal activity in the Gateses' home was well supported by the less speculative theory, noted in text, that if the informant [462 U.S. 213, 246] could predict with considerable accuracy the somewhat unusual travel plans of the Gateses, he probably also had a reliable basis for his statements that the Gateses kept a large quantity of drugs in their home and frequently were visited by other drug traffickers there.

JUSTICE WHITE, concurring in the judgment.

In my view, the question regarding modification of the exclusionary rule framed in our order of November 29, 1982, 459 U.S. 1028 (1982), is properly before us and should be addressed. I continue to believe that the exclusionary rule is an inappropriate remedy where law enforcement officials act in the reasonable belief that a search and seizure was consistent with the Fourth Amendment - a position I set forth in Stone v. Powell, 428 U.S. 465, 537-539 (1976). In this case, it was fully reasonable for the Bloomingdale, Ill., police to believe that their search of respondents' house and automobile comported with the Fourth Amendment as the search was conducted pursuant to a judicially issued warrant. The [462 U.S. 213, 247] exclusion of probative evidence where the constable has not blundered not only sets the criminal free but also fails to serve any constitutional interest in securing compliance with the important requirements of the Fourth Amendment. On this basis, I concur in the Court's judgment that the decision of the Illinois Supreme Court must be reversed.

I

The Court declines to address the exclusionary rule question because the Illinois courts were not invited to modify the rule in the first instance. The Court's refusal to face this important question cannot be ascribed to jurisdictional limitations. I fully agree that the statute which gives us jurisdiction in this cause, 28 U.S.C. 1257(3), prevents us from deciding federal constitutional claims raised here for the first time on review of state-court decisions. Cardinale v. Louisiana, 394 U.S. 437, 438-439 (1969). But it is equally well established that "`[n]o particular form of words or phrases is essential, but only that the claim of invalidity and the ground therefor be brought to the attention of the state court with fair precision and in due time.'" Street v. New York, 394 U.S. 576, 584 (1969) (quoting New York ex rel. Bryant v. Zimmerman, 278 U.S. 63, 67 (1928)). Notwithstanding the select and controversial instances in which the Court has reversed a state-court decision for "plain error,"1 we have consistently dismissed for want of jurisdiction where the federal claim asserted in this Court was not raised below. But this obviously is not such a case. As the Court points out, "[i]t is clear in this case that respondents expressly raised, at every level of the Illinois judicial system, the claim that the Fourth Amendment had been violated by the actions of the Illinois [462 U.S. 213, 248] police and that the evidence seized by the officers should be excluded from their trial." Ante, at 220. Until today, we have not required more.

The presentation and decision of respondents' Fourth Amendment claim fully embraces the argument that due to the nature of the alleged Fourth Amendment violation, the seized evidence should not be excluded. Our decisions concerning the scope of the exclusionary rule cannot be divorced from the Fourth Amendment; they rest on the relationship of Fourth Amendment interests to the objectives of the criminal justice system. See, e. g., United States v. Ceccolini, 435 U.S. 268 (1978); Stone v. Powell, 428 U.S. 465 (1976).4 Similarly, the issues surrounding a proposed good-faith modification are intricately and inseverably tied to the nature of the Fourth Amendment violation: the degree of probable cause, the presence of a warrant, and the clarity of previously announced Fourth Amendment principles all inform the [462 U.S. 213, 250] good-faith issue. The Court's own holding that the duty of a reviewing court is simply to ensure that the magistrate had a "substantial basis" for concluding that probable cause existed, ante, at 244-245, is itself but a variation on the good-faith theme. See Brief for Petitioner on Reargument 4-26.

As a jurisdictional requirement, I have no doubt that the exclusionary rule question is before us as an indivisible element of the claim that the Constitution requires exclusion of certain evidence seized in violation of the Fourth Amendment. As a prudential matter, I am unmoved by the Court's lengthy discourse as to why it must avoid the question. First, the Court turns on its head the axiom that "`due regard for the appropriate relationship of this Court to state courts,' McGoldrick v. Compagnie Generale Transatlantique, 309 U.S., at 434-435, demands that those courts be given an opportunity to consider the constitutionality of the actions of state officials," ante, at 221. This statement, written to explain why a state statute should not be struck down on federal grounds not raised in the state courts,5 hardly applies when the question is whether a rule of federal law articulated by this Court should now be narrowed to reduce the scope of federal intrusion into the State's administration of criminal justice. Insofar as modifications of the federal exclusionary [462 U.S. 213, 251] rule are concerned, the Illinois courts are bound by this Court's pronouncements. Cf. Oregon v. Hass, 420 U.S. 714, 719 (1975). I see little point in requiring a litigant to request a state court to overrule or modify one of this Court's precedents. Far from encouraging the stability of our precedents, the Court's proposed practice could well undercut stare decisis. Either the presentation of such issues to the lower courts will be a completely futile gesture or the lower courts are now invited to depart from this Court's decisions whenever they conclude such a modification is in order.6

The Court correctly notes that Illinois may choose to pursue a different course with respect to the state exclusionary rule. If this Court were to formulate a "good-faith" exception to the federal exclusionary rule, the Illinois Supreme Court would be free to consider on remand whether the state exclusionary rule should be modified accordingly. The possibility that it might have relied upon the state exclusionary rule had the "good-faith" question been posed does not constitute independent and adequate state grounds. "The possibility that the state court might have reached the same conclusion if it had decided the question purely as a matter of state law does not create an adequate and independent state ground that relieves this Court of the necessity of considering the federal question." United Air Lines, Inc. v. Mahin, 410 U.S. 623, 630-631 (1973); Beecher v. Alabama, 389 U.S. 35, 37, n. 3 (1967); C. Wright, The Law of Federal Courts 107, pp. 747-748 (4th ed. 1983). Nor does having the state court first decide whether the federal exclusionary rule should be modified - and presentation of the federal question does not insure that the equivalent state-law issue will be [462 U.S. 213, 252] raised or decided7 - avoid the unnecessary decision of a federal question. The Court still must reach a federal question to decide the instant case. Thus, in today's opinion, the Court eschews modification of the exclusionary rule in favor of interring the test established by Aguilar v. Texas, 378 U.S. 108 (1964), and Spinelli v. United States, 393 U.S. 410 (1969). Nor is the exclusionary rule question avoided - it is simply deferred until "another day."

It also appears that the Court, in disposing of the case, does not strictly follow its own prudential advice. The Illinois Supreme Court found not only a violation of the Fourth Amendment but also of Article I, 6, of the Illinois Constitution, which also provides assurance against unreasonable searches and seizures. Taking the Court's new prudential standards on their own terms, the Illinois courts should be given the opportunity to consider in the first instance whether a "totality of the circumstances" test should replace the more precise rules of Aguilar and Spinelli. The Illinois Supreme Court may decide to retain the established test for purposes of the State Constitution just as easily as it could decide to retain an unmodified exclusionary rule.8

Finally, the Court correctly notes that a fully developed record is helpful if not indispensable for the decision of many issues. I too resist the decision of a constitutional question [462 U.S. 213, 253] when such guidance is necessary, but the question of whether the exclusionary rule should be modified is an issue of law which obviously goes far beyond and depends little on the subjective good faith of the police officers that searched the Gateses' property. Moreover, the case comes here with a fully developed record as to the actions of the Bloomingdale, Ill., police. If further factual development of whether the officers in this case acted in good faith were important, that issue should logically be considered on remand, following this Court's statement of the proper legal standards.9

The Court's straining to avoid coming to grips with the exclusionary rule issue today may be hard for the country to understand - particularly given earlier statements by some Members of the Court.10 The question has been fully briefed and argued by the parties and amici curiae, including the United States.11 The issue is central to the enforcement of law and the administration of justice throughout the Nation. The Court of Appeals for the second largest Federal Circuit [462 U.S. 213, 254] has already adopted such an exception, United States v. Williams, 622 F.2d 830 (CA5 1980) (en banc), cert. denied, 449 U.S. 1127 (1981), and the new Eleventh Circuit is presumably bound by its decision. Several Members of this Court have for some time expressed the need to consider modifying the exclusionary rule, ante, at 224, and Congress as well has been active in exploring the question. See The Exclusionary Rule Bills, Hearings on S. 101, S. 751, and S. 1995 before the Subcommittee on Criminal Law of the Senate Committee on the Judiciary, 97th Cong., 1st and 2d Sess. (1981-1982). At least one State has already enacted a good-faith exception. Colo. Rev. Stat. 16-3-308 (Supp. 1982). Of course, if there is a jurisdictional barrier to deciding the issue, none of these considerations are relevant. But if no such procedural obstacle exists, I see it as our responsibility to end the uncertainty and decide whether the rule will be modified. The question of whether probable cause existed for the issuance of a warrant and whether the evidence seized must be excluded in this case should follow our reconsideration of the framework by which such issues, as they arise from the Fourth Amendment, are to be handled.

II

A

The exclusionary rule is a remedy adopted by this Court to effectuate the Fourth Amendment right of citizens "to be secure in their persons, houses, papers and effects, against unreasonable searches and seizures . . . ." Although early opinions suggested that the Constitution required exclusion of all illegally obtained evidence, the exclusionary rule "has never been interpreted to proscribe the introduction of illegally seized evidence in all proceedings or against all persons." Stone v. Powell, 428 U.S., at 486. Because of the inherent trustworthiness of seized tangible evidence and the resulting social costs from its loss through suppression, application [462 U.S. 213, 255] of the exclusionary rule has been carefully "restricted to those areas where its remedial objectives are thought most efficaciously served." United States v. Calandra, 414 U.S. 338, 348 (1974). Even at criminal trials the exclusionary rule has not been applied indiscriminately to ban all illegally obtained evidence without regard to the costs and benefits of doing so. Infra, at 256-257. These developments, born of years of experience with the exclusionary rule in operation, forcefully suggest that the exclusionary rule be more generally modified to permit the introduction of evidence obtained in the reasonable good-faith belief that a search or seizure was in accord with the Fourth Amendment.

This evolvement in the understanding of the proper scope of the exclusionary rule embraces several lines of cases. First, standing to invoke the exclusionary rule has been limited to situations where the government seeks to use such evidence against the victim of the unlawful search. Brown v. United States, 411 U.S. 223 (1973); Alderman v. United States, 394 U.S. 165 (1969); Wong Sun v. United States, 371 U.S. 471, 491-492 (1963); Rakas v. Illinois, 439 U.S. 128 (1978).

Second, the rule has not been applied in proceedings other than the trial itself. In United States v. Calandra, supra, the Court refused to extend the rule to grand jury proceedings. "Any incremental deterrent effect which might be achieved by extending the rule to grand jury proceedings is uncertain at best. . . . We therefore decline to embrace a view that would achieve a speculative and undoubtedly minimal advance in the deterrence of police misconduct at the expense of substantially impeding the role of the grand jury." 414 U.S., at 351-352. Similarly, in United States v. Janis, 428 U.S. 433 (1976), the exclusionary rule was not extended to forbid the use in federal civil proceedings of evidence illegally seized by state officials, since the likelihood of deterring unlawful police conduct was not sufficient to outweigh the social costs imposed by the exclusion. [462 U.S. 213, 256]

Third, even at a criminal trial, the same analysis has led us to conclude that the costs of excluding probative evidence outweighed the deterrence benefits in several circumstances. We have refused to prohibit the use of illegally seized evidence for the purpose of impeaching a defendant who testifies in his own behalf. United States v. Havens, 446 U.S. 620 (1980); Walder v. United States, 347 U.S. 62 (1954). We have also declined to adopt a "per se or `but for' rule" that would make inadmissible any evidence which comes to light through a chain of causation that began with an illegal arrest. Brown v. Illinois, 422 U.S. 590, 603 (1975). And we have held that testimony of a live witness may be admitted, notwithstanding that the testimony was derived from a concededly unconstitutional search. United States v. Ceccolini, 435 U.S. 268 (1978). Nor is exclusion required when law enforcement agents act in good-faith reliance upon a statute or ordinance that is subsequently held to be unconstitutional. United States v. Peltier, 422 U.S. 531 (1975); Michigan v. DeFillippo, 443 U.S. 31 (1979).12 Cf. United States v. Caceres, 440 U.S. 741, 754-757 (1979) (exclusion not [462 U.S. 213, 257] required of evidence tainted by violation of an executive department's rules concerning electronic eavesdropping).

A similar balancing approach is employed in our decisions limiting the scope of the exclusionary remedy for Fifth Amendment violations, Oregon v. Hass, 420 U.S. 714 (1975); Harris v. New York, 401 U.S. 222 (1971); Michigan v. Tucker, 417 U.S. 433 (1974), and our cases considering whether Fourth Amendment decisions should be applied retroactively, United States v. Peltier, supra, at 538-539; Williams v. United States, 401 U.S. 646, 654-655 (1971) (plurality opinion); Desist v. United States, 394 U.S. 244, 249-250 (1969); Linkletter v. Walker, 381 U.S. 618, 636-639 (1965). But see United States v. Johnson, 457 U.S. 537 (1982).

These cases reflect that the exclusion of evidence is not a personal constitutional right but a remedy, which, like all remedies, must be sensitive to the costs and benefits of its imposition. The trend and direction of our exclusionary rule decisions indicate not a lesser concern with safeguarding the Fourth Amendment but a fuller appreciation of the high costs incurred when probative, reliable evidence is barred because of investigative error. The primary cost, of course, is that the exclusionary rule interferes with the truthseeking function of a criminal trial by barring relevant and trustworthy evidence.13 We will never know how many guilty defendants go free as a result of the rule's operation. But any rule of evidence that denies the jury access to clearly probative and reliable evidence must bear a heavy burden of justification, [462 U.S. 213, 258] and must be carefully limited to the circumstances in which it will pay its way by deterring official lawlessness. I do not presume that modification of the exclusionary rule will, by itself, significantly reduce the crime rate - but that is no excuse for indiscriminate application of the rule.

The suppression doctrine entails other costs as well. It would be surprising if the suppression of evidence garnered in good faith, but by means later found to violate the Fourth Amendment, did not deter legitimate as well as unlawful police activities. To the extent the rule operates to discourage police from reasonable and proper investigative actions, it hinders the solution and even the prevention of crime. A tremendous burden is also placed on the state and federal judicial systems. One study reveals that one-third of federal defendants going to trial file Fourth Amendment suppression motions, and 70% to 90% of these involve formal hearings. General Accounting Office, Comptroller General of the United States, Impact of the Exclusionary Rule on Federal Criminal Prosecutions 10 (1979).

The rule also exacts a heavy price in undermining public confidence in the reasonableness of the standards that govern the criminal justice system. "[A]lthough the [exclusionary] rule is thought to deter unlawful police activity in part through the nurturing of respect for Fourth Amendment values, if applied indiscriminately it may well have the opposite effect of generating disrespect for the law and the administration of justice." Stone v. Powell, 428 U.S., at 490-491. As JUSTICE POWELL observed in Stone v. Powell, supra, at 490: "The disparity in particular cases between the error committed by the police officer and the windfall afforded a guilty defendant by application of the rule is contrary to the idea of proportionality that is essential to the concept of justice."

B

There are several types of Fourth Amendment violations that may be said to fall under the rubric of "good faith." "[T]here will be those occasions where the trial or appellate court will disagree on the issue of probable cause, no matter how reasonable the grounds for arrest appeared to the officer and though reasonable men could easily differ on the question. It also happens that after the events at issue have occurred, the law may change, dramatically or ever so slightly, but in any event sufficiently to require the trial judge to hold that there was not probable cause to make the arrest and to seize the evidence offered by the prosecution. . . ." Stone v. Powell, 428 U.S., at 539-540 (WHITE, J., dissenting). The argument for a good-faith exception is strongest, however, when law enforcement officers have reasonably relied on a judicially issued search warrant.

This Court has never set forth a rationale for applying the exclusionary rule to suppress evidence obtained pursuant to a search warrant; it has simply done so without considering whether Fourth Amendment interests will be advanced. It is my view that they generally will not be. When officers have dutifully obtained a search warrant from a judge or magistrate, and execute the warrant as directed by its terms, exclusion of the evidence thus obtained cannot be expected to deter future reliance on such warrants. The warrant is prima facie proof that the officers acted reasonably in conducting the search or seizure; "[o]nce the warrant issues, there is literally nothing more that the policeman can do in seeking to comply with the law." Stone v. Powell, supra, at 498 (BURGER, C. J., concurring).16 AS JUSTICE STEVENS [462 U.S. 213, 263] put it in writing for the Court in United States v. Ross, 456 U.S. 798, 823, n. 32 (1982): "[A] warrant issued by a magistrate normally suffices to establish" that a law enforcement officer has "acted in good faith in conducting the search." Nevertheless, the warrant may be invalidated because of a technical defect or because, as in this case, the judge issued a warrant on information later determined to fall short of probable cause. Excluding evidence for these reasons can have no possible deterrent effect on future police conduct, unless it is to make officers less willing to do their duty. Indeed, applying the exclusionary rule to warrant searches may well reduce incentives for police to utilize the preferred warrant procedure when a warrantless search may be permissible under one of the established exceptions to the warrant requirement. See ante, at 236; Brown v. Illinois, 422 U.S., at 611, and n. 3 (POWELL, J., concurring in part); P. Johnson, New Approaches to Enforcing the Fourth Amendment 11 (unpublished paper, 1978). See also United States v. United States District Court, 407 U.S. 297, 316-317 (1972); United States v. Ventresca, 380 U.S. 102, 106-107 (1965).

Opponents of the proposed "reasonable belief" exception suggest that such a modification would allow magistrates and judges to flout the probable-cause requirements in issuing warrants. This is a novel concept: the exclusionary rule was adopted to deter unlawful searches by police, not to punish the errors of magistrates and judges. Magistrates must be neutral and detached from law enforcement operations and I would not presume that a modification of the exclusionary rule will lead magistrates to abdicate their responsibility to apply the law.17 In any event, I would apply the exclusionary [462 U.S. 213, 264] rule when it is plainly evident that a magistrate or judge had no business issuing a warrant. See, e. g., Aguilar v. Texas, 378 U.S. 108 (1964); Nathanson v. United States, 290 U.S. 41 (1933). Similarly, the good-faith exception would not apply if the material presented to the magistrate or judge is false or misleading, Franks v. Delaware, 438 U.S. 154 (1978), or so clearly lacking in probable cause that no well-trained officer could reasonably have thought that a warrant should issue.

Another objection is that a reasonable-belief exception will encompass all searches and seizures on the frontier of the Fourth Amendment and that such cases will escape review on the question of whether the officer's action was permissible, denying needed guidance from the courts and freezing Fourth Amendment law in its present state. These fears are unjustified. The premise of the argument is that a court must first decide the reasonable-belief issue before turning to the question of whether a Fourth Amendment violation has occurred. I see no need for such an inflexible practice. When a Fourth Amendment case presents a novel question of law whose resolution is necessary to guide future action by law enforcement officers and magistrates, there is sufficient reason for the Court to decide the violation issue before turning to the good-faith question. Indeed, it may be difficult to [462 U.S. 213, 265] determine whether the officers acted reasonably until the Fourth Amendment issue is resolved.18 In other circumstances, however, a suppression motion poses no Fourth Amendment question of broad import - the issue is simply whether the facts in a given case amounted to probable cause - in these cases, it would be prudent for a reviewing court to immediately turn to the question of whether the officers acted in good faith. Upon finding that they had, there would generally be no need to consider the probable-cause question. I doubt that our Fourth Amendment jurisprudence would suffer thereby. It is not entirely clear to me that the law in this area has benefited from the constant pressure of fully litigated suppression motions. The result usually has been that initially bright-line rules have disappeared in a sea of ever-finer distinctions. Moreover, there is much to be said for having Fourth Amendment jurisprudence [462 U.S. 213, 266] evolve in part, albeit perhaps at a slower pace, in other settings.19

Finally, it is contended that a good-faith exception will be difficult to apply in practice. This concern appears grounded in the assumption that courts would inquire into the subjective belief of the law enforcement officers involved. I would eschew such investigations. "[S]ending state and federal courts on an expedition into the minds of police officers would produce a grave and fruitless misallocation of judicial resources." Massachusetts v. Painten, 389 U.S. 560, 565 (1968) (WHITE, J., dissenting). Moreover, "[s]ubjective intent alone . . . does not make otherwise lawful conduct illegal or unconstitutional." Scott v. United States, 436 U.S. 128, 136 (1978). Just last Term, we modified the qualified immunity public officials enjoy in suits seeking damages against federal officials for alleged deprivations of constitutional rights, eliminating the subjective component of the standard. See Harlow v. Fitzgerald, 457 U.S. 800 (1982). Although [462 U.S. 213, 267] searches pursuant to a warrant will rarely require any deep inquiry into reasonableness, I would measure the reasonableness of a particular search or seizure only by objective standards. Even for warrantless searches, the requirement should be no more difficult to apply than the closely related good-faith test which governs civil suits under 42 U.S.C. 1983. In addition, the burden will likely be offset by the reduction in the number of cases which will require elongated considerations of the probable-cause question, and will be greatly outweighed by the advantages in limiting the bite of the exclusionary rule to the field in which it is most likely to have its intended effects.

III

Since a majority of the Court deems it inappropriate to address the good-faith issue, I briefly address the question that the Court does reach - whether the warrant authorizing the search and seizure of respondents' car and home was constitutionally valid. Abandoning the "two-pronged test" of Aguilar v. Texas, 378 U.S. 108 (1964), and Spinelli v. United States, 393 U.S. 410 (1969), the Court upholds the validity of the warrant under a new "totality of the circumstances" approach. Although I agree that the warrant should be upheld, I reach this conclusion in accordance with the Aguilar-Spinelli framework.

A

For present purposes, the Aguilar-Spinelli rules can be summed up as follows. First, an affidavit based on an informant's tip, standing alone, cannot provide probable cause for issuance of a warrant unless the tip includes information that apprises the magistrate of the informant's basis for concluding that the contraband is where he claims it is (the "basis of knowledge" prong), and the affiant informs the magistrate of his basis for believing that the informant is credible (the "veracity" prong). Aguilar, supra, at 114; [462 U.S. 213, 268] Spinelli, supra, at 412-413, 416.20 Second, if a tip fails under either or both of the two prongs, probable cause may yet be established by independent police investigatory work that corroborates the tip to such an extent that it supports "both the inference that the informer was generally trustworthy and that he made his charge . . . on the basis of information obtained in a reliable way." Spinelli, supra, at 417. In instances where the officers rely on corroboration, the ultimate question is whether the corroborated tip "is as trustworthy as a tip which would pass Aguilar's tests without independent corroboration." 393 U.S., at 415.

Even, however, had the corroboration related only to completely innocuous activities, this fact alone would not preclude the issuance of a valid warrant. The critical issue is not whether the activities, observed by the police are innocent or suspicious. Instead, the proper focus should be on whether the actions of the suspects, whatever their nature, give rise to an inference that the informant is credible and that he obtained his information in a reliable manner.

Thus, in Draper v. United States, 358 U.S. 307 (1959), an informant stated on September 7 that Draper would be carrying narcotics when he arrived by train in Denver on the morning of September 8 or September 9. The informant also provided the police with a detailed physical description [462 U.S. 213, 270] of the clothes Draper would be wearing when he alighted from the train. The police observed Draper leaving a train on the morning of September 9, and he was wearing the precise clothing described by the informant. The Court held that the police had probable cause to arrest Draper at this point, even though the police had seen nothing more than the totally innocent act of a man getting off a train carrying a briefcase. As we later explained in Spinelli, the important point was that the corroboration showed both that the informant was credible, i. e., that he "had not been fabricating his report out of whole cloth," Spinelli, 393 U.S., at 417, and that he had an adequate basis of knowledge for his allegations, "since the report was o