WASHINGTON – Federal, state and local law enforcement agencies conducting criminal investigations collected data on cellphone activity thousands of times last year, with each request to a phone company yielding hundreds or thousands of phone numbers of innocent Americans along with those of potential suspects.
Law enforcement made more than 9,000 requests last year for what are called tower dumps, information on all the calls that bounced off a cellphone tower within a certain period of time, usually two or more hours, a congressional inquiry has revealed.
The inquiry, by Sen. Edward Markey, D-Mass., into law enforcements use of cellphone data comes amid growing scrutiny of the bulk collection of geolocation data overseas and of Americans phone records in the United States by the National Security Agency.
Tower dumps raise in the law enforcement context some of the same concerns presented by the NSAs mass collection of phone records without a warrant, when large amounts of data on law-abiding citizens are gathered to find clues about a small number of suspects, privacy advocates and some industry lawyers say. But unlike the NSA collection, which is bound by court-imposed rules on retention and use, the standards for obtaining tower data and the limits on its use by a plethora of agencies are inconsistent and unclear.
This isnt the NSA asking for information, said Markey, who is planning to introduce legislation this month to restrict law enforcements use of consumers phone data, including ensuring that tower dumps are narrowly focused. Its your neighborhood police department requesting your mobile phone data. So there are serious questions about how law enforcement handles the information of innocent people swept up in these digital dragnets.
Markeys investigation, based on a survey of eight U.S. phone companies, has also revealed that carriers, following requests from law enforcement agencies, are providing a range of other records as well. Those include GPS location data, website addresses and, in some cases, the search terms Americans have entered into their cellphones.
Markeys legislation, which does not focus on NSA or other intelligence agencies programs, would require a warrant to obtain GPS location data, impose limits on how long carriers can keep customers phone data, and mandate routine disclosures by law enforcement agencies on the nature and volume of requests they make of carriers. The proposal would not require a warrant for tower dumps.
Markey is pushing for standardized rules on law enforcements use of cellphone data, which has come under question in the courts. One federal judge this year, in a rare public ruling, required a warrant for tower dumps.
Some companies Markey surveyed did not provide full responses. But in general, the survey reflects a greater reliance on cellphone data of all types, including text messages and call histories, by law enforcement.
The industry as a whole in recent years experienced a substantial increase in these demands: the number of requests to Verizon Wireless has approximately doubled in the last five years, a trend that appears to be consistent with the industry in general, the companys general counsel, William Petersen, said in letter to Markey.
Tower dumps violate the privacy of hundreds or thousands of innocent people at a time, most of whom will never learn their location information was obtained by the government in order to find the proverbial needle in the haystack, said Christopher Soghoian, principal technologist at the American Civil Liberties Union.