What is the legal test for establishing probable cause in a search warrant application based on unverified information from an untested or unreliable informant?

Corroboration is required for unverified information from an untested or unreliable informant. " Because unverified information from an untested or unreliable informant is ordinarily unreliable, it does not establish probable cause unless it is "corroborated in essential respects by other facts, sources or circumstances." [Citations.] " ( People v. Gotfried (2003) 107 Cal.App.4th 254, 263, 131 Cal.Rptr.2d 840.) Adequate corroboration is found where police investigation has uncovered indications of criminal activity consistent with the informant's information. " Even observations of seemingly innocent activity provide sufficient corroboration if the anonymous tip casts the activity in a suspicious light. " ( Id. at p. 264, 131 Cal.Rptr.2d 840.)

Lastly, "The opinions of an experienced officer may legitimately be considered by the magistrate in making the probable cause determination." ( People v. Deutsch (1996) 44 Cal.App.4th 1224, 1232, 52 Cal.Rptr.2d 366.)

Our examination of the in camera proceedings indicates the trial court made no effort to ascertain the reliability of the prosecution's confidential information. Instead, the trial court accepted the prosecution's claims of reliability at face value. No percipient witnesses were called and the prosecution relied on hearsay testimony. No other corroborating evidence of the serious charge against defendant was presented.⁶ The dangers of hearsay evidence in informant affidavits are well-known. "[A]lthough hearsay may be relied upon in seeking a search warrant, the hearsay has little value where the informant is untested and the information is uncorroborated and lacking in detail." ( People v. French, supra, 201 Cal.App.4th at p. 1317, 134 Cal.Rptr.3d 383.)