Wis. Stat. § 968.35: Application for an order for a pen register or a trap and trace device.

(1) The attorney general or a district attorney may make application for an order or an extension of an order under s. 968.36 authorizing or approving the installation and use of a pen register or a trap and trace device, in writing under oath or equivalent affirmation, to a circuit court for the county where the device is to be located.

(2) An application under sub. (1) shall include all of the following:

(a) The identity of the person making the application and the identity of the law enforcement agency conducting the investigation.

(b) A certification by the applicant that the information likely to be obtained is relevant to an ongoing criminal investigation being conducted by that agency.