The question of whether law enforcement requires a warrant before accessing location data from mobile device providers hinges in great measure on whether the devices meet the legal definition of "tracking devices," says a Dec. 1 report from the Congressional Research Service.

If a cellphone is not a "tracking device," then location information generated by it can't be sought under the Stored Communications Act, the CRS report says. The SCA is a part of the Electronic Communications Privacy Act of 1986; it requires the government to obtain a warrant when it seeks the contents of wire or electronic communications that have been in storage less than 180 days, but permits law enforcement to compel a service provider to turn over a record of other information related to a subscriber if there are "reasonable grounds" to believe that the contents of electronic communication are relevant to an ongoing criminal investigation.

In 2010, the Third Circuit reversed two lower court opinions holding that a cellphone is a tracking device because it can locate--independently of the presence of Global Positioning Satellite capability on the phone--the user to within 50 feet of cellphone towers.  

More recently, a judge in the Southern District of Texas held in a Nov. 11 order (.pdf) that a cellphone does indeed constitute a tracking device, and further that location data from it isn't covered by the SCA, since the SCA definition of electronic communication excludes tracking devices. It can't be wire communication either, the judge held, "because a wire communication involves the 'human voice.'" As a result, the traditional requirement for a warrant applies.

The government at times has argued that the SCA and the Pen Register Statue combine to permit it to gain real-time access to location information, the CRS report adds. Pen Register/Trap Trace Statute, also a part of the Electronic Communications Privacy Act, permits law enforcement to capture the numbers dialed to and from a telephone without knowing the contents of the telephone calls. Under the Patriot Act, the government also received expanded authority to record "signaling information."  

Under the Pen Register Statue, it's possible that location information fits within the definition of signaling information, but another law, the Communications Assistance for Law Enforcement Act of 1994 prohibits the government from accessing location information solely pursuant to pen register or trap and trace devices, the report says.

Under a "hybrid theory" that combines Pen Register and the SCA, the government has argued that since the SCA permits disclosure by an electronic communication service of subscriber data, location data can be given to law enforcement since information on the location of cell towers is not the service cellphone users have subscribed to. The Pen/Trap statue then then permits the disclosure of that information in real time.

"Most jurisdictions have rejected" the hybrid theory, the report states, and "a majority of the courts require law enforcement to obtain a warrant to access cell location information."

For more:
- download the CRS report form the FAS website (.pdf)

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