by John Marshall Harlan

“ The central point of the discussion of probable cause in Aguilar is, as perhaps more precisely emphasized by our explicit twin holdings in Spinelli, see 393 U.S., at 416, 89 S.Ct., at 589, that the two elements necessary to establish the informer's trustworthiness-namely, that the tip relayed to the magistrate be both truthful and reliable-are analytically severable. It is not possible to argue that since certain information, if true, would be trustworthy, therefore, it must be true. ”

“ The Government's first contention misconceives the basic thrust of this Court's decisions in the Nathanson, Giordenello, Aguilar, Spinelli, and Whiteley cases, supra. The central proposition common to each of these decisions is that the determination of probable cause is to be made by the magistrate, not the affiant. That the agent-affiant determined the informer to be prudent cannot be a basis for sustaining this warrant unless magistrates are entitled to delegate their responsibilities to law enforcement officials. ”

“ In the case before us, no one maintains that the magistrate's judgment as to elements (a) and (b) was not properly supported. Plainly the information set forth in the affidavit, if entitled to credit, establishes probable cause. And the magistrate was certainly entitled to rely on the agent's official status, his personal observation of the agent, and the oath administered to him by the magistrate in concluding that the affiant's assertions as to what he had been told by the informer were credible. ”

“ It would, indeed, be anomalous if the Fourth Amendment dictated such results, for it surely was never intended as a hindrance to fair, vigorous law enforcement. Further, I think there is much truth in the Government's supporting assertion that the ordinary citizen who has never before reported a crime to the police may, in fact, be more reliable than one who supplies information on a regular basis. ”

“ It is true that in Nathanson the Court was not dealing with the sufficiency of the allegations respecting one or more of the above-described components of probable cause, but merely with a bare overall statement of the affiant that probable cause existed. Further, as the Government notes, our chief, but not sole, emphasis in Aguilar was upon the absence of any evidence communicated by the affiant from which a magistrate could infer that the confidant gathered his evidence from a reliable source. ”

“ Such an assertion, however, is no more than a conclusion which the Constitution requires must be drawn independently by the magistrate. What this portion of the affidavit lacks are any of the underlying 'facts or circumstances' that informed the agent's conclusion and whose presentation to the magistrate would enable him to assess the probability that this determination was sufficiently plausible to justify authorizing a search of respondent's premises. ”

“ Finally, we have not found any instance of the application of this rule where the witness declined to reveal to the trier of fact the identity of the declarant, presumably because without this knowledge it cannot be readily assumed that the declarant might have had reason to suspect the use of the statement would do him harm. Thus, while strict rules of evidence certainly do not govern magistrates' assessments of probable cause, it would require a rather extensive relaxation of them to permit reliance on this factor. ”

“ Surely there is no reason to suspect that this indicates the confidant anticipated potential perjury proceedings if he were subsequently proved a liar. Nor does that assertion reveal, in any meaningful sense, what sort of relationship this might have reflected or created between the agent and his informer.↑ The Court of Appeals in reversing respondent's conviction stated that ' (t) he allegation that (the informant) is a 'prudent person' signifies that he is circumspect in the conduct of his affairs, but reveals nothing about his credibility.' 412 F.2d 796, at 797-798. ”