3rd Circuit to Mull Privacy of Cell Phone Data, Shannon P. Duffy: “In a case that could prove to be one of the most important privacy rights battles of the modern era, the 3rd U.S. Circuit Court of Appeals will hear argument this week on the proper legal standard to apply when prosecutors demand cell phone location data. The data, which are recorded about once every seven seconds whenever a cell phone is turned on, effectively track the whereabouts and the comings and goings of every cell phone user. Justice Department lawyers argue that, by statute, they need only show “reasonable grounds” to believe that such records are “relevant and material to an ongoing criminal investigation.” But a federal magistrate judge in Pittsburgh strongly disagreed in February 2008, issuing a 52-page opinion that said the prosecutors must meet the “probable cause” standard.”