WASHINGTON -- In the first public accounting of its kind, cell phone carriers reported that they responded to a startling 1.3 million demands for subscriber data last year from law enforcement agencies seeking text messages, caller locations and other information in the course of investigations.
The data, which come in response to a congressional inquiry, document an explosion in cell phone surveillance in the last five years, with wireless carriers turning over records thousands of times a day in response to police emergencies, court orders, law enforcement subpoenas and other requests.
The cell phone carriers' 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 FBI.
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 -- even surprised some officials who have closely followed the growth of cell surveillance.
"I never expected it to be this massive," said Rep. Edward Markey, a Massachusetts Democrat who requested the data 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 various 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 230 emergency requests a day nationwide -- triple the number it fielded in 2007, the company told Mr. Markey. Law enforcement requests of all kinds have been rising quickly among the other carriers as well, with annual increases of between 12 percent and 16 percent in the last five years. Sprint led the way last year, reporting more than 500,000 law enforcement requests for data.
With the rapid expansion of cell surveillance have come rising concerns -- including among the carriers -- about what legal safeguards are in place to balance law enforcement agencies' needs for quick information 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 the courts. The next year, the FBI 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 cell phones have blurred the lines on what is legally required to get data -- particularly the use of GPS systems to identify the location of cell phones.
Mr. Markey and other Democrats are considering legislation that they say would more clearly draw the line between giving the authorities the technological tools they need and protecting the privacy of the public. With the rising prevalence of cell phones, officials at all levels of law enforcement say cell tracking represents a powerful tool to find suspects, follow leads, identify associates and cull information on a wide range of crimes.
Because of incomplete record-keeping, the total number of law enforcement requests last year was most likely higher than the 1.3 million, the carriers reported to Mr. Markey. Also, the total number of people whose customer information was turned over could be several times higher than the number of requests because a single request often involves multiple callers.
For instance, when a police agency asks for a cell tower "dump" for data on subscribers who were near a tower during a certain period of time, it may get back hundreds or even thousands of names.
As cell surveillance increased, warrants for wiretapping by federal and local officials -- eavesdropping on conversations -- declined 14 percent last year to 2,732, according to a recent report from the Administrative Office of the United States Courts.
The diverging numbers suggest that law enforcement officials are shifting away from wiretaps in favor of other forms of cell tracking that are generally less legally burdensome, less time consuming and less costly.
To handle the demands, most cell carriers reported employing large teams of in-house lawyers, data technicians, phone "cloning specialists" and others around the clock to take requests from law enforcement agencies, review the legality and provide the data.