WASHINGTON — In the first public accounting of its kind, cellphone carriers reported that they responded to a startling 1.3 million demands for subscriber information last year from law enforcement agencies seeking text messages, caller locations and other information in the course of investigations.
The cellphone carriers’ reports, which come in response to a Congressional inquiry, document an explosion in cellphone surveillance in the last five years, with the companies turning over records thousands of times a day in response to police emergencies, court orders, law enforcement subpoenas and other requests.
The reports also reveal a sometimes uneasy partnership with law enforcement agencies, with the carriers frequently rejecting demands that they considered legally questionable or unjustified. At least one carrier even referred some inappropriate requests to the F.B.I.
The information represents the first time data have been collected nationally on the frequency of cell surveillance by law enforcement. The volume of the requests reported by the carriers — which most likely involve several million subscribers — surprised even some officials who have closely followed the growth of cell surveillance.
“I never expected it to be this massive,” said Representative Edward J. Markey, a Massachusetts Democrat who requested the reports from nine carriers, including AT&T, Sprint, T-Mobile and Verizon, in response to an article in April in The New York Times on law enforcement’s expanded use of cell tracking. Mr. Markey, who is the co-chairman of the Bipartisan Congressional Privacy Caucus, made the carriers’ responses available to The Times.
While the cell companies did not break down the types of law enforcement agencies collecting the data, they made clear that the widened cell surveillance cut across all levels of government — from run-of-the-mill street crimes handled by local police departments to financial crimes and intelligence investigations at the state and federal levels.
AT&T alone now responds to an average of more than 700 requests a day, with about 230 of them regarded as emergencies that do not require the normal court orders and subpoena. That is roughly triple the number it fielded in 2007, the company said. Law enforcement requests of all kinds have been rising among the other carriers as well, with annual increases of between 12 percent and 16 percent in the last five years. Sprint, which did not break down its figures in as much detail as other carriers, led all companies last year in reporting what amounted to at least 1,500 data requests on average a day.
With the rapid expansion of cell surveillance have come rising concerns — including among carriers — about what legal safeguards are in place to balance law enforcement agencies’ needs for quick data against the privacy rights of consumers.
Legal conflicts between those competing needs have flared before, but usually on national security matters. In 2006, phone companies that cooperated in the Bush administration’s secret program of eavesdropping on suspicious international communications without court warrants were sued, and ultimately were given immunity by Congress with the backing of the courts. The next year, the F.B.I. was widely criticized for improperly using emergency letters to the phone companies to gather records on thousands of phone numbers in counterterrorism investigations that did not involve emergencies.
Under federal law, the carriers said they generally required a search warrant, a court order or a formal subpoena to release information about a subscriber. But in cases that law enforcement officials deem an emergency, a less formal request is often enough. Moreover, rapid technological changes in cellphones have blurred the lines on what is legally required to get data — particularly the use of GPS systems to identify the location of phones.
As cell surveillance becomes a seemingly routine part of police work, Mr. Markey said in an interview that he worried that “digital dragnets” threatened to compromise the privacy of many customers. “There’s a real danger we’ve already crossed the line,” he said.