— Or more likely you can't un-ring the phone.
United States v. Thomas, 2009 U.S. Dist. LEXIS 4389, No.08-cr-87-bbc-02 (W.D. Wis. January 20, 2009), is of interest for several reasons: the use of cellphone tracking technology, and application of the recent U.S. Supreme Court decision in Herring v. United States.
First for the techies. Police were investigating a bank robbery involving four suspects. As a result of some astute investigating they interviewed a potential suspects mother. During the interview she told the police about some cellphone calls, in particular a lot of calls from one number where she didn't know the caller. Acting on a hunch, a good hunch as it turned out, police then obtained a trap and trace warrant on that cellphone number. Police then used some sophisticated equipment.