Probable Cause

Probable Cause is the major element supporting the issuance of a search warrant. Courts have said probable cause is based on common sense rooted in the "the factual and practical considerations of everyday life on which reasonable and prudent men, not legal technicians, act." This means that formulating complex rules should not be the method used by the courts in determining probable cause since it is not a difficult concept to recognize and does not require hyper technical description.[1]

“Totality of Circumstances” Test.

The test dictated by the Supreme Court used to evaluate facts offered to support probable cause in search warrants is called the totality of circumstances test.[2] This test requires a court to look at the summation of all of the factual assertions in the affidavit, giving the weight each deserves, in assessing the totality of the circumstances. Its application invalidates the warrant only if the totality fails to establish probable cause.[3]

Information in the affidavit to support probable cause may come from the person or police officer requesting the warrant, or from other police officers, or members of the public. The information received from members of the public is said to come from informants, and specific rules regarding how to evaluate that information regarding its reliability and trustworthiness are outlined by case law.

Citizen Informant.

The information received from victims and witnesses to a crime is presumed reliable even though little may be known about the particular person conveying the information.[4] This is because they usually have no motive other than cooperating with the police in gathering facts concerning the criminal act witness by each. They are citizen informants.

To qualify as a citizen informant the affidavit must state the reasons a person should be entitled to that classification. The citizen informant’s reliability applies only to the credibility or trustworthiness of the person supplying the information and not necessarily the value of it. [5]

Other informants not considered citizen informants must be shown dependable by the inclusions in the affidavit of details establishing that requirement.

Unidentified Informant.

Often informants are not identified in the affidavit, usually because they are working with the police who wish to protect their identity. For information received through unidentified informants to be consider reliable, it must come from an informant known to the police and who has supplied consistently accurate information to police on prior occasions.[6] The affidavit must supply facts that support this conclusion for a reviewer to conclude the information is reliable.


If all or some of the information in the affidavit comes from informants unknown to the police they must include in the affidavit the reasons the informant should be believed, and their information considered trustworthy. [7]

Adequate police corroboration must pertain to the alleged criminal activity used to support the warrant and merely accurate information about the suspect is not sufficient. These include, “Pedestrian facts” such as a suspect's physical description, residence, and vehicles are not sufficient corroboration. [8]

[1] Brinegar v. United States, 338 U.S. 160, 175 (1949).

[2] Aguilar v. Texas (1964) 378 U.S. 108, 84 S.Ct. 1509, 1512, 12 L.Ed.2d 723, 729;People v. Smith (1976) 17 C.3d 845, 850, 132 C.R. 397, 553 P.2d 557; People v. McCarter (1981) 117 C.A.3d 894, 902, 173 C.R. 188; Fenwick & West v. Superior Court (1996) 43 C.A.4th 1272, 1277, 1278, 51 C.R.2d 294

[3] Illinois v Gates (1983) 462 U.S. 213, 103 S.Ct. 2317, 2332, 76 L.Ed.2d 527, 548, infra, §135; Massachusetts v. Upton (1984) 466 U.S. 727, 104 S.Ct. 2085, 2087, 80 L.Ed.2d 721, 726.

[4] Humphrey v. Appellate Div. (2002) 29 C.4th 569, 575, 576, 127 C.R.2d 645, 58 P.3d 476.

[5] Bailey v. Superior Court (1992) 11 C.A.4th 1107

[6] United States v. Harris (1971) 403 U.S. 573, 91 S.Ct. 2075, 2080, 29 L.Ed.2d 723, 731

[7] People v. Superior Court (Johnson) (1972) 6 C.3d 704, 712, 100 C.R. 319, 493 P.2d 1183

[8] People v. French (2011) 201 C.A.4th 1307, 1319, 134 C.R.3d 383