California Code, Penal Code - PEN § 638.53

(1) There are grounds upon which an order could be issued under Section 638.52.

(2) There is probable cause to believe that an emergency situation exists with respect to the investigation of a crime.

(3) There is probable cause to believe that a substantial danger to life or limb exists justifying the authorization for immediate installation and use of a pen register or a trap and trace device before an order authorizing the installation and use can, with due diligence, be submitted and acted upon.

(b)(1) By midnight of the second full court day after the pen register or trap and trace device is installed, a written application pursuant to Section 638.52 shall be submitted by the peace officer who made the oral application to the magistrate who orally approved the installation and use of a pen register or trap and trace device. If an order is issued pursuant to Section 638.52, the order shall also recite the time of the oral approval under subdivision (a) and shall be retroactive to the time of the original oral approval.

(2) In the absence of an authorizing order pursuant to paragraph (1), the use shall immediately terminate when the information sought is obtained, when the application for the order is denied, or by midnight of the second full court day after the pen register or trap and trace device is installed, whichever is earlier.