UPDATE:  Audio files of the oral argument in this appeal are available on the Web site of the U.S. Court of Appeals for the Third Circuit.

If the FBI wants to know where an individual is, and if the Department of Justice prevails in a case rescheduled for argument tomorrow in snowy Philadelphia, the FBI (or other law enforcement authorities) will be able to obtain that individual’s cell site data from the individual’s cellular carrier on a showing of “reasonable grounds” to believe that the data is “relevant and material to an ongoing investigation.” This is an issue that may have important implications for law enforcement, with significant impact on wireless carrier operations (and costs), and dramatic implications for privacy in the wireless world.  In In re Application of the United States of America, No. 08-4227 (Third Cir.), attorneys for the Electronic Frontier Foundation, arguing as amicus curiae, will urge the appeals court to uphold a lower court ruling that applications for cell site data should be supported by a showing that satisfies the higher probable cause standard under the Fourth Amendment.