Court Rules That Police Cannot Use Warrants to Obtain Cell Phone Location of Person Who is Subject of Arrest Warrant

From The Volokh Conspiracy:

Imagine the police have an arrest warrant for a crime suspect, and they want to find the suspect to arrest him. They happen to know the suspect’s cell phone number, so they want to go to the phone company and have the phone company tell the police the location of the suspect’s phone. The phone company refuses to let the police get that information without a warrant, so the police police go to a judge and apply for a search warrant based on the probable cause to believe that the location of the phone will help them execute the arrest warrant. Here’s the interesting question: Should the judge sign the warrant application and issue the warrant? Or should the judge deny the warrant application?

On August 3, Magistrate Judge Susan K. Gauvey issued a fascinating opinion on this novel question: IN THE MATTER OF AN APPLICATION OF THE UNITED STATES OF AMERICA FOR AN ORDER AUTHORIZING DISCLOSURE OF LOCATION INFORMATION OF A SPECIFIED WIRELESS TELEPHONE, 2011 U.S. Dist. LEXIS 85638 (D.Md. 2011). Her answer: The Judge must deny the warrant application, as location information is broadly protected by the Fourth Amendment and government cannot use warrants to find out the location of people who have warrants out for their arrest. The timing of the case is extremely unusual, as it seems the case is moot and this is only an advisory opinion. If I understand the timing, Magistrate Judge Gauvey denied the application over a year ago, and the government was able to arrest the suspect some other way in the meantime. Judge Gauvey decided to hand down an opinion on the legal issue anyway, appointed defense counsel to argue for defense interests, and now, a year later, has handed down the opinion on why she denied that application back in 2010.