In Carpenter, the FBI was was investigating a string of robberies in and around Detroit in 2011. In order to link the defendant to the crimes, the government obtained 127 days of his cell phone records from MetroPCS—without a warrant—to try to place him at the locations of the robberies. As in other cases, the government argued that Mr. Carpenter had no reasonable expectation of privacy in these records, which it claimed were simultaneously incriminating but not precise enough to reveal his exact location and movements over those 127 days. The district court and Sixth Circuit court of appeals agreed, holding individuals lack any privacy interest in the location information generated by their cell phones.

Carpenter successfully petitioned the Supreme Court to review his case. EFF filed briefs both encouraging the Court to take the case and urging it to reject the Third Party Doctrine on the merits. We noted that cell phone usage has exploded in the last 30 years, and with it, the technologies to locate users have gotten ever more precise. 

In 2018, the Supreme Court agreed. In an opinion by Chief Justice Roberts that cited EFF's brief, the Court recognized that location information, collected by cell providers like Sprint, AT&T, and Verizon, creates a “detailed chronicle of a person’s physical presence compiled every day, every moment over years.” As a result, police must now get a warrant before obtaining this data.