The ACLU received over 5,700 pages of documents from roughly 250 local law enforcement agencies regarding cell phone tracking. The responses show that while cell phone tracking is routine, few agencies consistently obtain warrants. Importantly, however, some agencies do obtain warrants, showing that law enforcement agencies can protect Americans' privacy while also meeting law enforcement needs.
The government responses varied widely, and many agencies did not respond at all. The documents included statements of policy, memos, police requests to cell phone companies (sometimes in the form of a subpoena or warrant), and invoices and manuals from cell phone companies explaining their procedures and prices for turning over the location data.
The overwhelming majority of the roughly 250 law enforcement agencies that provided documents engaged in at least some cell phone tracking — and many track cell phones quite frequently. Most law enforcement agencies explained that they track cell phones to investigate crimes. Some said they tracked cell phones only in emergencies, for example to locate a missing person. Only 13 said they have never tracked cell phones.
Many law enforcement agencies track cell phones quite frequently. For example, based on invoices from cell phone companies, it appears that Raleigh, N.C. tracks hundreds of cell phones a year. The practice is so common that cell phone companies have manuals for police explaining what data the companies store, how much they charge police to access that data, and what officers need to do to get it.
Most law enforcement agencies do not obtain a warrant to track cell phones, but some do, and the legal standards used vary widely. Some police departments protect privacy by obtaining a warrant based upon probable cause when tracking cell phones. For example, police in the Riverside County, CA, Denver, the County of Hawaii, Wichita, and Lexington, Ky. demonstrate probable cause and obtain a warrant when tracking cell phones. If these police departments can protect both public safety and privacy by meeting the warrant and probable cause requirements, then surely other agencies can as well.
Unfortunately, other departments do not always demonstrate probable cause and obtain a warrant when tracking cell phones. For example, police in Lincoln, Neb. obtain even GPS location data, which is more precise than cell tower location information, on telephones without demonstrating probable cause. Police in Wilson County, N.C. obtain historical cell tracking data where it is "relevant and material" to an ongoing investigation, a standard lower than probable cause.
Police use various methods to track cell phones. Most commonly, law enforcement agencies obtain cell phone records about one person from a cell phone carrier. However, some police departments, like in Gilbert, Ariz., have purchased their own cell tracking technology.
Sometimes, law enforcement agencies obtainall of the cell phone numbers at a particular location at a particular time. For example, a law enforcement agent in Tucson, Ariz. prepared a memo for fellow officers explaining how to obtain this data. And records from Cary, N.C. include a request for all phones that utilized particular cell phone towers.
Cell phone companies have worsened the lack of transparency by law enforcement by hiding how long they store location data. Cell phone companies store customers' location data for a very long time. According to the U.S. Department of Justice, Sprint keeps location tracking records for 18-24 months, and AT&T holds onto them "since July 2008," suggesting they are stored indefinitely. Yet none of the major cell phone providers disclose to their customers the length of time they keep their customers' cell tracking data. Mobile carriers owe it to their customers to be more forthright about what they are doing with our data.
>>ACLU Open Letter to Wireless Carriers on Location Tracking of Cell Phones