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Warrant Required for Cell-Tower Tracking Data, Supreme Court Rules

Given that carrying and using a cell phone is pretty much a requirement of participation in modern society, and that the amount of data phone companies can collect via the towers our phones are constantly "pinging" for a signal, the location data of our phones can provide quite the window into our daily lives. And if law enforcement wants to peek through that window, they need a warrant according to the Supreme Court.

Today, the Court ruled that police must obtain a warrant to get a phone's location information from cell towers, in certain circumstances. But not every justice agreed with the majority. You can read all the Supreme Court's reasoning right here.

Phone Data and Personal Data

While investigating the alleged mastermind of a series of armed robberies of electronics stores, law enforcement asked for and received over four months' worth of cell-site tower data, tracking a suspect's phone to almost 13,000 locations, from the robbery sites to his home and his church. This range of personal information implicated the Fourth Amendment's restrictions on searches, and therefore required police and prosecutors to obtain a warrant.

"Mapping a cell phone's location over the course of 127 days provides an all-encompassing record of the holder's whereabouts," according to Chief Justice John Roberts. "As with GPS information, the timestamped data provides an intimate window into a person's life, revealing not only his particular movements, but through them his 'familial, political, professional, religious, and sexual associations.'"

When a Warrant Is Required

While law enforcement might be able to gather cell-site location records in real time, for an amount of time shorter than this case, in response to emergencies, or about all the phones connected to a particular tower at a particular time without a warrant, if police are asking cell phone companies for location data on a particular phone for an extended amount of time, the Supreme Court ruled, they must obtain a valid warrant first.

You can see the full opinion below:

Carpenter v United States by FindLaw on Scribd