On June 22, the U.S. Supreme Court has ruled that police require a search warrant to perform cellphone tower searches. In other words, in order for law enforcement to track your past whereabouts—through historical cellphone location—will need a judge’s approval.
The 5-4 ruling was written by conservative Chief Justice John Roberts, who sided with the four liberal justices. That reversed and remanded a Sixth Circuit Court of Appeals decision.
Carpenter v. United States is the first case regarding phone location data that the Supreme Court has ruled on. This case initially came to light back in 2014 when Carpenter was convicted of multiple armed robberies in 2010 and 201, resulting in a 116-year prison sentence.
The verdict was made after the prosecution gained access to Carpenter’s cell-location data based on the Stored Communications Act of 1986, not a search warrant. The act allows phone companies to turn over records if the government has reasonable grounds to believe they will aid a criminal investigation.
Lower courts determined that collection of cellphone location data is legal based on the “third party doctrine," which is based on prior Supreme Court cases which upheld law enforcement access to suspects’ bank records and phone numbers. The theory goes that consumers should know that phone companies can keep track of them, so their locations are not considered private.
However, Chief Justice Roberts wrote the government’s searches of Carpenter’s phone records were deemed a Fourth Amendment search. He said permitting government access to GPS data violates Carpenter’s Fourth Amendment rights, by providing police officers with his entire location history.
"While the third-party doctrine applies to landline telephone numbers and bank records, it is not clear whether its logic extends to the qualitatively different category of cell-site records. Given the unique nature of cell phone location records, the fact that the information is held by a third party does not by itself overcome the user's claim to Fourth Amendment protection...The location information obtained from Carpenter's wireless carriers was the product of a search."
Keep in mind, the ruling does not affect law enforcement’s ability to track someone in real time using cell data, specifically referring to fleeing suspects.
The ruling is a substantial victory for advocates of increased privacy rights who argued further protections were necessary with regard to the government obtaining information from a third party, such as a cellphone company.