Supreme Court Rules that Obtaining Cell Site Location Information Is a Search

On Friday, the Supreme Court issued a long-awaited opinion in Carpenter v. United States. The Court held that when law enforcement obtains long-term cell site location information from a suspect’s service provider, it conducts a Fourth Amendment search that normally requires a warrant. Although the majority opinion states that it “is a narrow one,” the dissenting Justices and some scholars see it as a seismic shift that may have many aftershocks. I’ll summarize the case and then use former Secretary of Defense Donald Rumsfeld’s famous approach to address the “known knowns,” the “known unknowns,” and the “unknown unknowns” after Carpenter. Facts. Carpenter was suspected of participating in a series of store robberies in Michigan and Ohio. The FBI sought and obtained two court orders requiring Carpenter’s cell phone service providers to produce records about Carpenter’s account, including cell site location information. One order covered 152 days, though for reasons not given in the opinion, the service provider only produced records for 127 days. The second order covered seven days, but the service provider only produced records for two days. The cell site location information put Carpenter in the vicinity of several robberies and became important evidence against him. Procedural history. Carpenter moved to suppress the records, arguing that he had a reasonable expectation of privacy in the records and in the location information that they revealed; that the FBI had therefore engaged in a search, for Fourth Amendment purposes, when agents obtained the records; and that the agents had acted without [...]