“When the government tracks the location of a cell phone,” writes Chief Justice John Roberts, “it achieves near perfect surveillance, as if it had attached an ankle monitor to the phone’s user.”
The observation comes in Carpenter v. U.S., a case the U.S. Supreme Court recently decided on a 5-4 vote. The decision acknowledges “seismic shifts in digital technology” that have changed so much of modern life.
The case involved a man accused in a string of robberies that took place in Ohio and Michigan. The police augmented their case against the man using cellphone location data which they obtained using an ordinary court order instead of a warrant. The police used 127 days’ worth of detailed tracking information essentially to surveil the defendant after the fact. The data placed him at each of the locations of the robberies.
The defendant challenged the police’s use of the data without a warrant. Warrants are meant to protect private citizens from undue police intrusion, as judges are supposed to independently verify that there is probable cause to believe a crime is being committed, has been committed or is about to be committed. This is called probable cause.
The trial and appellate courts found, however, that no warrant was required for the records. This is because of a 1986 case that ruled that warrants are not required to obtain business records held by third parties like phone companies. However, that case was decided long before cellphones were common, and the phone records involved were just a list of calls to and from a specific landline — nothing like the detailed records available today.
Today’s phone records are “detailed, encyclopedic and effortlessly compiled,” according to Chief Justice Roberts, and can often reveal the user’s exact physical movements in GPS detail. Individuals have a legitimate expectation of privacy in such records, the majority ruled, so a warrant is required before accessing them.
That said, the court made clear that it was not abandoning the third-party business records rule. Many other types of records — including bank records — can still be obtained via a simple court order. Additionally, police are allowed to obtain cellphone location data without a warrant in emergency situations.
“This is a groundbreaking victory for Americans’ privacy rights in the digital age,” said the ACLU attorney who argued the case. “The Supreme Court has given privacy law an update that it has badly needed for many years, finally bringing it in line with the realities of modern life.”