Supreme Court Cases on Probable Cause

A fundamental principle of search and seizure law is that a warrant to search property in which the owner has a reasonable expectation of privacy shall not be issued absent a sufficient basis for finding probable cause to believe that contraband or evidence is located in a particular place. (See Aguilar v. Texas (1964) 378 U.S. 108, 115-116 (Aguilar); see also Illinois v. Gates (1983) 462 U.S. 213 at p. 230.) The Fourth Amendment requires that the judicial officer issuing the warrant be supplied with sufficient information to support an independent judgment that probable cause exists for the warrant. (Whiteley v. Warden (1971) 401 U.S. 560, 564,; see 1525 "a search warrant cannot be issued but upon probable cause, supported by affidavit".) In Aguilar and Spinelli v. United States (1969) 393 U.S. 410 (Spinelli), the United States Supreme Court set forth two requirements for affidavits containing hearsay information provided to the affiant by an unidentified informant: (1) the magistrate must be informed of some of the underlying circumstances from which the informant concluded that the contraband is where he claims it is (the "basis of knowledge" prong), and (2) the magistrate must be informed of some of the underlying circumstances from which the affiant concluded that the informant is credible or his information reliable (the "veracity" prong). (Aguilar, supra, 378 U.S. at p. 114; Spinelli, supra, 393 U.S. at pp. 412-413.) In Gates, the court overruled the rigid two-pronged rule of Aguilar and Spinelli, but it stated that the elements under the two-pronged test concerning the informant's veracity, reliability, and basis of knowledge "are all highly relevant in determining the value of his report." (Gates, supra, 462 U.S. at p. 230.) Gates said that courts should continue to place reliance upon the elaboration of these elements, not "as entirely separate and independent requirements to be rigidly exacted in every case," but rather as "closely intertwined issues that may usefully illuminate the commonsense, practical question whether there is 'probable cause' to believe that contraband or evidence is located in a particular place." (Ibid.) The Gates "totality-of-the-circumstances analysis . . . permits a balanced assessment of the relative weights of all the various indicia of reliability (and unreliability) attending an informant's tip . . . ." (Gates, supra, 462 U.S. at p. 234.) For example, the extreme reliability of an informant and his predictions of criminal activity may compensate for a failure to set forth completely the informant's basis of knowledge in a particular affidavit. (Id. at p. 233.) On the other hand, an explicit and detailed description of an alleged wrongdoing, along with a statement that an event was personally observed may warrant that greater weight be given to an informant's tip even if there is "some doubt" about the informant's reliability. (Id. at p. 234.) When no other indicia of the informant's credibility or veracity are available, independent police investigation corroborating allegations of criminal activity by an informant is an indispensable element for determining the reliability of an informant's allegations. (Gates, supra, 462 U.S. at pp. 238-239.)