WASHINGTON — Law enforcement tracking of cellphones, once the province mainly of federal agents, has grown into a powerful and widely used surveillance tool for local police officials as well, with hundreds of departments, large and small, often using it with little or no court oversight, new documents show.
The practice has become big business for cellphone companies, with a handful of carriers marketing a catalog of "surveillance fees" to police departments to determine suspects' locations, trace phone calls and texts, or provide other services.
With cellphones now nearly ubiquitous, police describe phone tracing as an increasingly valuable weapon in a range of cases, including emergencies such as child abductions and suicide calls, and investigations into drug cases, sex crimes and slayings.
One California police manual describes cellphones as "the virtual biographer of our daily activities," providing a rich hunting ground for learning about someone's contacts and travels.
But civil liberties advocates say the widening use of cell tracking raises legal and constitutional questions, particularly when the police act without judicial orders.
While many departments require court warrants to use phone tracking in non-emergencies, others claim broad discretion to get the records on their own, according to 5,500 pages of internal records obtained by the American Civil Liberties Union from 205 police departments nationwide.
The documents, provided to The New York Times by the ACLU, open a window into a cloak-and-dagger practice that police officials are wary about discussing publicly.
While cell tracking by local police departments has received limited public attention in the past few years, the ACLU documents show that the practice is in wider use – with looser safeguards – than officials have previously acknowledged.
The police records show many departments struggling to understand and abide by the legal complexities of cellphone tracking, even as they exploit the technology.
In cities in North Carolina, Nevada and elsewhere, police departments have gotten wireless carriers to track cellphone signals back to cell towers as part of nonemergency investigations to identify all the callers using a particular tower, records show.
In California, state prosecutors advised local police departments on ways to get carriers to "clone" a phone and download text messages while it is turned off.
In Ogden, Utah, when the Sheriff's Department wants information on a cellphone, it leaves it up to the carrier to determine what the sheriff must provide.
"Some companies ask that when we have time to do so, we obtain court approval for the tracking request," the Sheriff's Department said in a written response to the ACLU.
In Arizona, even small police departments found cell surveillance so valuable that they acquired their own tracking equipment to avoid the time and expense of having phone companies carry out the operations. Police in Gilbert, for one, spent $244,000 on such equipment.
Cell carriers, staffed with law enforcement liaison teams, charge police departments from a few hundred dollars for locating a phone to more than $2,200 for a full-scale wiretap of a suspect, records show.
While cell tracing allows the police to get records and locations on users, the ACLU documents give no indication that departments have listened to phone calls without court warrants required under federal law.