THE FOURTH AMENDMENT protects Americans’ right to “be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures.” Does this protection extend to cellphone records documenting a person’s location? On Friday, the Supreme Court said yes; it ruled in a 5-to-4 decision that the government must get a warrant to track a person’s cell-site location information, offering a victory to digital privacy advocates in one of the most significant Fourth Amendment cases in recent years.
Carpenter v. United States hinged on the conviction of Timothy Carpenter, who was sentenced to 116 years in prison for participating in a series of burglaries in 2010 and 2011. Law-enforcement officials gathered 127 days’ worth of location records from Mr. Carpenter’s phone and used that to show he had been near the crime scenes. The American Civil Liberties Union, which took up Mr. Carpenter’s case, argued that this constituted a “search”; and as such, the government should have had to persuade a judge to issue a warrant before it could see the records. The four liberal justices joined Chief Justice John G. Roberts Jr., who wrote the majority opinion.
The court’s decision builds on previous rulings that uphold people’s expectations of privacy in their “physical location and movements.” The justices noted that cell-site records can track a person’s whereabouts at unprecedented levels of precision. The court also raised valid concerns about the retrospective nature of cellphone location data: With unconstrained access to this information, the government could “travel back in time” to track people’s locations. “Only the few without cell phones could escape this tireless and absolute surveillance,” wrote Mr. Roberts in the majority opinion.
The Justice Department had argued that, under the “third-party doctrine,” people relinquish the expectation of privacy when they choose to share information with third parties, including cellphone service providers. But the doctrine was developed during the 1960s and 1970s — well before the advent of modern cellphones. Do most American expect their service provider to store location data for up to five years and offer these records to law enforcement without warrants? In an era when cellphones have become ubiquitous enough to be considered “a feature of human anatomy,” could they realistically choose to avoid cellphones altogether? As the court ruled, probably not.
The Carpenter decision reflects a broader shift in the