Cal. Penal Code § 1526

(a) The magistrate, before issuing the warrant, may examine on oath the person seeking the warrant and any witnesses the person may produce, and shall take his or her affidavit or their affidavits in writing, and cause the affidavit or affidavits to be subscribed by the party or parties making them.

(b) In lieu of the written affidavit required in subdivision (a), the magistrate may take an oral statement under oath under one of the following conditions: (1) The oath shall be made under penalty of perjury and recorded and transcribed. The transcribed statement shall be deemed to be an affidavit for the purposes of this chapter. In these cases, the recording of the sworn oral statement and the transcribed statement shall be certified by the magistrate receiving it and shall be filed with the clerk of the court. In the alternative in these cases, the sworn oral statement shall be recorded by a certified court reporter and the transcript of the statement shall be certified by the reporter, after which the magistrate receiving it shall certify the transcript which shall be filed with the clerk of the court. (2) The oath is made using telephone and facsimile transmission equipment, telephone and electronic mail, or telephone and computer server, as follows: (A) The oath is made during a telephone conversation with the magistrate, whereafter the affiant shall sign his or her affidavit in support of the application for the search warrant. The affiant’s signature shall be in the form of a digital signature or electronic signature if electronic mail or computer server is used for transmission to the magistrate. The proposed search warrant and all supporting affidavits and attachments shall then be transmitted to the magistrate utilizing facsimile transmission equipment, electronic mail, or computer server. (B) The magistrate shall confirm with the affiant the receipt of the search warrant and the supporting affidavits and attachments. The magistrate shall verify that all the pages sent have been received, that all pages are legible, and that the affiant’s signature, digital signature, or electronic signature is acknowledged as genuine. (C) If the magistrate decides to issue the search warrant, he or she shall: (i) Sign the warrant. The magistrate’s signature may be in the form of a digital signature or electronic signature if electronic mail or computer server is used for transmission to the magistrate. (ii) Note on the warrant the exact date and time of the issuance of the warrant. (iii) Indicate on the warrant that the oath of the affiant was administered orally over the telephone. The completed search warrant, as signed by the magistrate, shall be deemed to be the original warrant. (D) The magistrate shall transmit via facsimile transmission equipment, electronic mail, or computer server, the signed search warrant to the affiant who shall telephonically acknowledge its receipt. The magistrate shall then telephonically authorize the affiant to write the words “duplicate original” on the copy of the completed search warrant transmitted to the affiant and this document shall be deemed to be a duplicate original search warrant. The duplicate original warrant and any affidavits or attachments in support thereof shall be returned as provided in Section 1534.