MR. JUSTICE GOLDBERG delivered the opinion of the Court.Respondent Ventresca was convicted in the United States District Court for the District of Massachusetts of possessing and operating an illegal distillery.  The conviction was reversed by the Court of Appeals (one judge dissenting) on the ground that the affidavit for a search warrant pursuant to which the still was found was insufficient to establish probable cause.  324 F.2d 864.The affidavit upon which the warrant was issued was made and submitted to a United States Commissioner on August 31, 1961, by Walter Mazaka, an Investigator for the Alcohol and Tobacco Tax Division of the Internal Revenue Service.  He stated that he had reason to believe that an illegal distillery was in operation in respondent, Ventresca's, house at 148 1/2 Coburn Avenue in Worcester, Massachusetts.  The grounds for this belief were set forth in detail in the affidavit, prefaced with the following statement:"Based upon observations made by me, and based upon information received officially from other Investigators attached to the Alcohol and Tobacco Tax Division assigned to this investigation, and reports orally made to me describing the results of their Page 380 U. S. 104 observations and investigation, this request for the issuance of a search warrant is made."The affidavit then described seven different occasions between July 28 and August 30, 1961, when a Pontiac car was driven into the yard to the rear of Ventresca's house.  On four occasions, the car carried loads of sugar in 60-pound bags; it made two trips loaded with empty tin cans; and once it was merely observed as being heavily laden.  Garry, the car's owner, and Incardone, a passenger, were seen on several occasions loading the car at Ventresca's house and later unloading apparently full five-gallon cans at Garry's house late in the evening.  On August 28, after a delivery of empty tin cans to Ventresca's house, Garry and Incardone were observed carrying from the house cans which appeared to be filled and placing them in the trunk of Garry's car.  The affidavit went on to state that, at about 4 a.m. on August 18, and at about 4 a.m. on August 30, "Investigators" smelled the odor of fermenting mash as they walked along the sidewalk in front of Ventresca's house.  On August 18, they heard, "[a]t or about the same time, . . . certain metallic noises."  On August 30, the day before the warrant was applied for, they heard (as they smelled the mash) "sounds similar to that of a motor or a pump coming from the direction of" Ventresca's house.  The affidavit concluded:"The foregoing information is based upon personal knowledge and information which has been obtained from Investigators of the Alcohol and Tobacco Tax Division, Internal Revenue Service, who had been assigned to this investigation."The District Court upheld the validity of the warrant on a motion to suppress.  The divided Court of Appeals held the warrant insufficient because it read the affidavit as not specifically stating in so many words that the information it contained was based upon the personal knowledge of Mazaka or other reliable investigators.  The Page 380 U. S. 105 Court of Appeals reasoned that all of the information recited in the affidavit might conceivably have been obtained by investigators other than Mazaka, and it could not be certain that the information of these other investigators was not, in turn, based upon hearsay received from unreliable informants, rather than their own personal observations.  For this reason, the court found that probable cause had not been established.  324 F.2d, at 868-870.  We granted certiorari to consider the standards by which a reviewing court should approach the interpretation of affidavits supporting warrants which have been duly issued by examining magistrates.  377 U.S. 989.  For the reasons stated below, we reverse the judgment of the Court of Appeals.IThe Fourth Amendment states:"The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized. [Footnote 1]"We begin our analysis of this constitutional rule mindful of the fact that, in this case, a search was made pursuant to a search warrant.  In discussing the Fourth Amendment policy against unnecessary invasions of privacy, we stated in Aguilar v. Texas, 378 U. S. 108:"An evaluation of the constitutionality of a search warrant should begin with the rule that 'the informed and deliberate determinations of magistrates empowered to issue warrants . . . are to be preferred Page 380 U. S. 106 over the hurried action of offices . . . who may happen to make arrests.'  United States v. Lefkowitz, 285 U. S. 452,  285 U. S. 464.  The reasons for this rule go to the foundations of the Fourth Amendment."378 U.S. at  378 U. S. 110-111.In Jones v. United States, 362 U. S. 257,  362 U. S. 270, this Court, strongly supporting the preference to be accorded searches under a warrant, indicated that, in a doubtful or marginal case, a search under a warrant may be sustainable where without one it would fall.  In Johnson v. United States, 333 U. S. 10, and Chapman v. United States, 365 U. S. 610, the Court, in condemning searches by officers who invaded premises without a warrant, plainly intimated that had the proper course of obtaining a warrant from a magistrate been followed, and had the magistrate, on the same evidence available to the police, made a finding of probable cause, the search under the warrant would have been sustained.  Mr Justice Jackson stated for the Court in Johnson:"The point of the Fourth Amendment, which often is not grasped by zealous officers, is not that it denies law enforcement the support of the usual inferences which reasonable men draw from evidence.  Its protection consists in requiring that those inferences 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.  Any assumption that evidence sufficient to support a magistrate's disinterested determination to issue a search warrant will justify the officers in making a search without a warrant would reduce the Amendment to a nullity and leave the people's homes secure only in the discretion of police officers."Johnson v. United States, supra, at  333 U. S. 13-14.The fact that exceptions to the requirement that searches and seizures be undertaken only after obtaining a warrant Page 380 U. S. 107 are limited [Footnote 2] underscores the preference accorded police action taken under a warrant as against searches and seizures without one.While a warrant may issue only upon a finding of "probable cause," this Court has long held that "the term "probable cause" . . . means less than evidence which would justify condemnation," Locke v. United States, 7 Cranch 339,  11 U. S. 348, and that a finding of "probable cause" may rest upon evidence which is not legally competent in a criminal trial.  Draper v. United States, 358 U. S. 307,  358 U. S. 311.  Page 380 U. S. 108 As the Court stated in Brinegar v. United States, 338 U. S. 160,  338 U. S. 173,"There is a large difference between the two things to be proved (guilt and probable cause), as well as between the tribunals which determine them, and therefore a like difference in the quanta and modes of proof required to establish them."Thus, hearsay may be the basis for issuance of the warrant "so long as there . . . [is] a substantial basis for crediting the hearsay."  Jones v. United States, supra, at  362 U. S. 272.  And, in Aguilar, we recognized that "an affidavit may be based on hearsay information and need not reflect the direct personal observations of the affiant," so long as the magistrate is "informed of some of the underlying circumstances" supporting the affiant's conclusions and his belief that any informant involved "whose identity need not be disclosed . . . " was "credible" or his information "reliable."  Aguilar v.Texas, supra, at  378 U. S. 114.These decisions reflect the recognition that the Fourth Amendment's commands, like all constitutional requirements, are practical and not abstract.  If the teachings of the Court's cases are to be followed and the constitutional policy served, affidavits for search warrants, such as the one involved here, must be tested and interpreted by magistrates and courts in a common sense and realistic fashion.  They are normally drafted by nonlawyers in the midst and haste of a criminal investigation.  Technical requirements of elaborate specificity once exacted under common law pleadings have no proper place in this area.  A grudging or negative attitude by reviewing courts toward warrants will tend to discourage police officers from submitting their evidence to a judicial officer before acting.This is not to say that probable cause can be made out by affidavits which are purely conclusory, stating only the affiant's or an informer's belief that probable cause exists without detailing any of the "underlying circumstances" Page 380 U. S. 109 upon which that belief is based.  See Aguilar v. Texas, supra.  Recital of some of the underlying circumstances in the affidavit is essential if the magistrate is to perform his detached function and not serve merely as a rubber stamp for the police.  However, where these circumstances are detailed, where reason for crediting the source of the information is given, and when a magistrate has found probable cause, the courts should not invalidate the warrant by interpreting the affidavit in a hypertechnical, rather than a common sense, manner.  Although 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.  Jones v. United States, supra, at  362 U. S. 270.IIThe application of the principles stated above leads us to reverse the Court of Appeals.  The affidavit in this case, if read in a common sense way, rather than technically, shows ample facts to establish probable cause and allow the Commissioner to issue the search warrant.  The affidavit at issue here, unlike the affidavit held insufficient in Aguilar, is detailed and specific.  It sets forth not merely "some of the underlying circumstances" supporting the officer's belief, but a good many of them.  This is apparent from the summary of the affidavit already recited, and from its text, which is reproduced in the 380 U.S. 102app|>Appendix.The Court of Appeals did not question the specificity of the affidavit.  It rested its holding that the affidavit was insufficient on the ground that"[t]he affidavit failed to clearly indicate which of the facts alleged therein were hearsay or which were within the affiant's own knowledge,"and therefore "[t]he Commissioner could only conclude that the entire affidavit was based on hearsay."  Page 380 U. S. 110 324 F.2d  at 868.  While the Court of Appeals recognized that an affidavit based on hearsay will be sufficient, "so long as a substantial basis for crediting the hearsay is presented," Jones v. United States, supra, at  362 U. S. 269, it felt that no such basis existed here because the hearsay consisted of reports by "Investigators," and the affidavit did not recite how the Investigators obtained their information.  The Court of Appeals conceded that the affidavit stated that the Investigators themselves smelled the odor of fermenting mash, but argued that the rest of their information might itself have been based upon hearsay thus raising "the distinct possibility of hearsay upon hearsay."  324 F.2d  at 869.  For this reason, it held that the affidavit did not establish probable cause.We disagree with the conclusion of the Court of Appeals.  Its determination that the affidavit might have been based wholly upon hearsay cannot be supported in light of the fact that Mazaka, a Government Investigator, swore under oath that the relevant information was in part based "upon observations made by me" and "upon personal knowledge," as well as upon"information which has been obtained from Investigators of the Alcohol and Tobacco Tax Division, Internal Revenue Service, who have been assigned to this investigation."It also seems to us that the assumption of the Court of Appeals that all of the information in Mazaka's affidavit may in fact have come from unreliable anonymous informers passed on to Government Investigators, who in turn related this information to Mazaka, is without foundation.  Mazaka swore that, insofar as the affidavit was not based upon his own observations, it was"based upon information received officially from other Investigators attached to the Alcohol and Tobacco Tax Division assigned to this investigation, and reports orally made to me describing the results of their observations and investigation."(Emphasis Page 380 U. S. 111 added.)  The Court of Appeals itself recognized that the affidavit stated that "Investigators' (employees of the Service) smelled the odor of fermenting mash in the vicinity of the suspected dwelling."  324 F.2d  at 869.  A qualified officer's detection of the smell of mash has often been held a very strong factor in determining that probable cause exists so as to allow issuance of a warrant. [Footnote 3]  Moreover, upon reading the affidavit as a whole, it becomes clear that the detailed observations recounted in the affidavit cannot fairly be regarded as having been made in any significant part by persons other than full-time Investigators of the Alcohol and Tobacco Tax Division of the Internal Revenue Service.  Observations of fellow officers of the Government engaged in a common investigation are plainly a reliable basis for a warrant applied for by one of their number. [Footnote 4]  We conclude that the affidavit showed probable cause, and that the Court of Appeals misapprehended its judicial function in reviewing this affidavit by giving it an unduly technical and restrictive reading.This Court is alert to invalidate unconstitutional searches and seizures whether with or without a warrant.  See Aguilar v. Texas, supra; Stanford v. Texas, 379 U. S. 476; Preston v. United States, 376 U. S. 364; Beck v. Ohio, 379 U. S. 89.  By doing so, it vindicates individual liberties and strengthens the administration of justice by promoting respect for law and order.  This Court is equally concerned to uphold the actions of law Page 380 U. S. 112 enforcement officers consistently following the proper constitutional course.  This is no less important to the administration of justice than the invalidation of convictions because of disregard of individual rights or official overreaching.  In our view, the officers in this case did what the Constitution requires.  They obtained a warrant from a judicial officer"upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the . . . things to be seized."It is vital that having done so their actions should be sustained under a system of justice responsive both to the needs of individual liberty and to the rights of the community.Reversed
U.S. Supreme CourtUnited States v. Ventresca, 380 U.S. 102 (1965)United States v. VentrescaNo. 28Argued January 18-19, 1965Decided March 1, 1965380 U.S. 102SyllabusAn Alcohol and Tobacco Tax Division Investigator made an affidavit stating his belief, on the basis of his own observations and the observations and investigation of other Investigators, that there was an illegal distillery operation in respondent's house.  The affidavit described different occasions when a car was driven to the rear of respondent's house with loads of sugar or empty tins; the loading at the house of apparently full five-gallon cans; the smelling by Investigators as they walked in front of the house of fermenting mash; and their hearing the sound of a motor pump and metallic noises from the direction of the house.  A Commissioner issued a search warrant on the basis of the affidavit, pursuant to which a still was found for the illegal possession and operation of which respondent was convicted.  The Court of Appeals reversed the conviction, holding the warrant insufficient to establish probable cause.Held:  The affidavit amply showed facts to establish probable cause to support the Commissioner's issuance of the search warrant.  Pp.  380 U. S. 105-111.(a) In a doubtful or marginal case, a search under a warrant may be sustainable where without one it would fall.  Pp.  380 U. S. 106-107.(b) An affidavit for a search warrant may be based on hearsay information so long as the magistrate is informed of some of the underlying circumstances supporting the affiant's conclusions and his belief that any informant involved, whose identity need not be disclosed, was credible or his information reliable.  Aguilar v. Texas, 378 U. S. 108, followed.  P.  380 U. S. 108.(c) Though, in order for a magistrate to perform his detached function of determining probable cause, an affidavit must recite the underlying circumstances, and not mere conclusions as to probable cause, the affidavit must be tested in a common sense way.  Pp.  380 U. S. 108-109.(d) Since a fair reading of the whole affidavit, which is detailed and specific, setting forth many of the underlying circumstances, reveals that its conclusions are substantially based upon observations Page 380 U. S. 103 of government officers, probable cause for the issuance of a warrant was shown.  Pp.  380 U. S. 110-111.324 F.2d 864, reversed.