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Washington Post: Agencies collected data on Americans’ cellphone use in thousands of ‘tower dumps’

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 little-known practice has raised concerns among federal judges, lawmakers and privacy advocates who question the harvesting of massive amounts of data on people suspected of no crime in order to try to locate a criminal. Data linked to specific cell towers can be used to track people’s movements.The inquiry, by Sen. Edward J. Markey (D-Mass.), into law enforcement’s 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 NSA’s 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 isn’t the NSA asking for information,” said Markey, who is planning to introduce legislation this month to restrict law enforcement’s use of consumers’ phone data, including ensuring that tower dumps are narrowly focused. “It’s 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.”