While the Senate considered an overhaul of a sweeping quarter-century-old law governing e-mail privacy, a House Judiciary Committee panel received dueling arguments on Thursday over when and how police can track the location of Americans carrying a cellphone.
For investigators, knowing where a suspect is and at what time can be crucial to an investigation. Cellphones have become a powerful tool for establishing those facts â€" one detective scheduled to testify on Capitol Hill Thursday described them in prepared remarks as a “witness†to a crime. Less clear is the law on how authorities can extract that information from cellphones.
Law enforcement officials say procuring a search warrant, based on probable cause, is too time-consuming and slows down an investigation.
“Geolocation evidence is essential to obtain in the early stages of investigations when probable cause has not been established,†Peter A. Modafferi, chief of detectives in Rockland County, N.Y., said in his written testimony posted on the committee’s Web site. “Requiring probable cause to get basic, limited information about a person’s historical location would make it significantly more difficult to solve crimes and seek justice for victims.â€
The law is vague on what information cellphone carriers must turn over to law enforcement and whether the officials require judicial review. Under what circumstances can police obtain a “tower dump,†meaning identify cellphone users whose devices pinged off a particular cellphone tower? Should a warrant be required to monitor the location of an individual with whom a known suspect is communicating? Should a warrant be required for specific location information of a known suspect?
There is no consensus in the law on these questions. In the confusion, the police across the country follow a wide range of practices, and courts have ruled in vastly different ways.
Pending legislation seeks to tighten privacy protections around the location data captured by cellphones. Thursday’s hearing aired a range of opinions on this.
Catherine Crump, a lawyer with the American Civil Liberties Union, described in her written remarks the modern cellphone as an “invasive yet inexpensive†way to track the movement of ordinary Americans. She said that the police should be required to obtain a search warrant to demonstrate they have a good reason to track someone’s whereabouts. “The warrant and probable cause requirements,†she said, “ensure that an objective magistrate determines that there is a good reason to believe that a search will turn up evidence of wrongdoing before mobile phone location data is disclosed.â€
The A.C.L.U., through a Freedom of Information Act request in 2010, discovered how long telecommunications carriers retained the location data of their users. Verizon reported at the time that it stores cell tower data for “one rolling year,†Ms. Crump told members of Congress; T-Mobile kept it “officially four to six monthsâ€; Sprint and Nextel for 18 to 24 months; and AT&T since July 2008.
The Supreme Court’s most important decision on location privacy came in January 2012, when the justices unanimously ruled that police had violated the Constitution’s protection from unreasonable search when they placed a Global Positioning System tracking device on a suspect’s car. They were divided on their rationale for the decision, but a majority suggested they were ambivalent about other forms of digital surveillance, including location data from cellphone towers.
