In the Matter of the Application of the United States of America

The United States government was performing a criminal investigation. As part of that investigation, government officials sought the cellular site location information (CSLI) of an individual. CSLI was information from telecommunications providers’ servers that could be used to locate cell phones in both real time and historically. Information would sometimes be gathered from one tower, multiple towers, or GPS information, which provided varying levels of accuracy. Thus, the government could use the CSLI to track the location of an individual. Federal law generally authorized electronic surveillance during investigations. Depending on the amount of intrusiveness, the government needed to make a higher showing to secure an order to lawfully use the investigative tool. For example, pen registers (i.e., devices that recorded whom someone called but not the contents of the call) required only a showing that the information likely to be obtained would lead to information relevant to the ongoing investigation. Wiretaps were on the other end of the spectrum, requiring the highest legal standard and specific procedural requirements beyond a probable-cause showing. Along this spectrum were tracking devices, which, because of their levels of intrusion, generally required not only probable cause but also specific notice requirements and other procedural mechanisms. These included certain procedural requirements enumerated in Federal Rule of Criminal Procedure (FRCP) 41. But the law did not specifically address the standard the government had to meet to obtain CSLI and whether that standard varied by how the information was obtained. The government argued that CSLI required less than probable cause and the same relevance standard as under the pen-register requirement.