What is the test for a search warrant?

In issuing a search warrant, there must be a "fair probability that contraband or evidence will be found in a particular place." (Illinois v. Gates (1983) 462 U.S. 213, 273.) The existence or nonexistence of probable cause is assessed by applying a "totality of the circumstances" test, which entails consideration of "the whole picture." (United States v. Cortez (1981) 449 U.S. 411, 417.)

"A magistrate's 'determination of probable cause should be paid great deference by reviewing courts.' " (Illinois v. Gates, supra, 462 U.S. at p. 236.) "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 . . . there is a fair probability that contraband or evidence of a crime will be found in a particular place." (Illinois v. Gates, supra, 462 U.S. at p. 238.) Where the affidavit provides sufficient information to enable the magistrate to act independently rather than merely ratifying the conclusions of the affiant, the affidavit is not legally insufficient. (Id. at p. 239.) "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." (United States v. Ventresca (1965) 380 U.S. 102, 109.)

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