On June 22, the U.S. Supreme Court said law enforcement generally needs a search warrant if it wants to track a person’s location through cellphone records of an extended period of time. The ruling was 5-4 with Chief Justice Roberts joining the court’s four liberals.
Now, the prosecution cannot obtain the location data of a suspect without written approval from a judge. Timothy Ivory Carpenter (Carpenter v. United States) argued that law enforcement violated his Fourth Amendment rights after gaining access of four months of location data, which showed he was near where armed robberies had occurred.
The case originated from a series of robberies in Michigan and Ohio in 2010 and 2011. In order to prosecute its case against Carpenter, the government obtained 127 days’ worth of cellphone records that revealed his approximate location, placing him in proximity to four of the crimes. In 2014, Carpenter was sentenced to 166 years in prison for multiple armed robberies.
Lower courts upheld the search of cell tower records based on the “third-party doctrine,” which was used in earlier Supreme Court cases to support government access to suspects’ bank records and phone numbers called from landlines. According to the theory, consumers should understand that wireless carriers can keep track of their locations, making them not private.
In the court’s opinion, Chief Justice John Roberts said, “a phone goes wherever its owner goes, conveying to the wireless carrier not just dialed digits, but a detailed and comprehensive record of the person's movements.”
When used for calls or texts, a cellphone signals a nearby antenna tower to connect with the telephone network. As the user travels, the call is handed off to successive towers, so that cellphone companies can keep records of the phone numbers routed through each tower to determine such things as roaming charges. By mapping out which towers were used by a specific phone number, law enforcement can reconstruct an individual’s whereabouts over days, weeks or months.
However, police can still obtain cellphone records without a warrant in such emergencies as “the need to pursue a fleeing suspect, protect individuals who are threatened with imminent harm, or prevent the imminent destruction of evidence.”
The ruling is a significant victory for privacy advocates in the United States. 95 percent of Americans own a cellphone.