(Bloomberg) -- Law enforcement officials generally need a warrant to get mobile-phone tower records that show someone’s location over an extended period, the U.S. Supreme Court ruled in a decision that bolsters digital privacy rights.
Voting 5-4, the court ruled Friday in favor of Timothy Ivory Carpenter, who said prosecutors violated the Constitution when they obtained four months of phone data and used it at trial to show he was near the sites of a string of armed robberies. Chief Justice John Roberts joined the court’s liberals in the majority.
The ruling could have a far-reaching impact. Prosecutors seek phone-location information from telecommunications companies in tens of thousands of cases a year. Prosecutors in most parts of the country had been able to demand that data from mobile-phone carriers without showing the "probable cause" required to get a warrant.
Writing for the court, Roberts pointed to the "depth, breadth and comprehensive reach" of the location data held by wireless companies.
"Mapping a cell phone’s location over the course of 127 days provides an all-encompassing record of the holder’s whereabouts," Roberts wrote. "As with GPS information, the time-stamped 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."
Justices Anthony Kennedy, Clarence Thomas, Samuel Alito and Neil Gorsuch dissented.
Roberts called the ruling a "narrow one" that focused on "the unique nature of cell phone location information" and the retrieval of historical data. He said the decision didn’t address whether police can use tower data to track someone in real time. He also said it wouldn’t block the acquisition of information if urgently needed to prevent violence or the destruction of evidence, or to help police pursue a fleeing suspect.
He also said the court was requiring a warrant only if officials seek at least a week’s worth of data and wasn’t ruling on efforts to collect information for shorter spans.
Even so, the court’s reasoning could have implications for government access to other types of information available on the cloud, including data from virtual assistants, smart thermostats and fitness trackers.
Technology companies -- including Apple Inc., Facebook Inc., Microsoft Corp., Verizon Communications Inc., Twitter Inc. and Google Inc. -- had urged the court to protect that data, though they didn’t explicitly take a position in the Carpenter case. Verizon spokesman Rich Young said the company had no immediate reaction to Friday’s ruling.
Carpenter is seeking to overturn his conviction for taking part in armed robberies of Detroit-area Radio Shacks and stores for wireless provider T-Mobile US Inc.
At trial, prosecutors used data obtained from Carpenter’s wireless carriers to show he was within a half-mile to two miles of the location of four of the robberies when they occurred. Mobile-phone companies typically keep records that show the cell sites where their customers’ calls begin and end.
The Justice Department declined to comment on the ruling. It had said law enforcement officials should be able to get location data without a warrant through the 1986 Stored Communications Act, which says prosecutors need only have "reasonable grounds" to believe the information would be useful in an investigation.
Roberts said the "reasonable grounds" standard wasn’t adequate, calling it "a gigantic departure from the probable cause rule."
Privacy advocates hailed the ruling. "This decision will provide users with the confidence that the sensitive location data they share with innovative digital devices and services will only be disclosed to law enforcement with a warrant,” Ed Black, president of the Computer & Communications Industry Association, said in a statement. The group’s members include Verizon, Facebook, Google, T-Mobile and Sprint Corp.
Nathan Freed Wessler, the American Civil Liberties Union attorney who argued the case on behalf of Carpenter, called the decision a "truly historic vindication of Americans’ privacy rights in the digital age."
In dissent, Kennedy said the ruling "puts needed, reasonable, accepted, lawful, and congressionally authorized criminal investigations at serious risk in serious cases."
Kennedy pointed to a 1979 decision that said the phone numbers a person dials aren’t constitutionally protected because the caller has already provided them to a third party -- that is, the phone company. He also invoked a 1976 ruling that let the government obtain financial information held by the bank of a man being investigated for tax evasion.
"The court has twice held that individuals have no Fourth Amendment interests in business records which are possessed, owned, and controlled by a third party," Kennedy wrote. He said the court had drawn "an unprincipled and unworkable line between cell-site records on the one hand and financial and telephonic records on the other."
Each of the four dissenters wrote his own opinion. Thomas urged the court to overturn the "reasonable expectation of privacy" test the court adopted in 1967. Gorsuch also questioned that test, while saying he might have sided with Carpenter had his lawyers focused on property rights instead.
Alito said the ruling "guarantees a blizzard of litigation while threatening many legitimate and valuable investigative practices upon which law enforcement has rightfully come to rely."
The Supreme Court ruling won’t necessarily overturn Carpenter’s conviction. The justices sent the case back to the lower courts to determine the next steps.
The case is Carpenter v. United States, 16-402.
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