On Friday, in a far-reaching decision, the Supreme Court ruled 5–4 that law enforcement must generally get a warrant in order to obtain an individual’s cell site location information—that is, records of every place your phone has been. The court’s decision dramatically both expands the scope of the Fourth Amendment and updates it for modern times, providing new and robust constitutional safeguards to the right to privacy. Indeed, the court’s decision in Carpenter v. United States may be the most important Fourth Amendment ruling of the 21st century so far.
Carpenter revolves around cell site location information (CSLI), which wireless carriers collect and store for business purposes. In recent years, CSLI has become extremely precise, tracking every movement your phone makes. For this reason, law enforcement often examines the CSLI of criminal suspects to glean information about their alleged misdeeds. Under a federal statute called the Stored Communications Act, the police may access an individual’s CSLI so long as they can provide “reasonable grounds” for believing the data is “relevant and material to an ongoing investigation.” The SCA does not require cops to get a warrant.
Timothy Carpenter, the defendant here, was convicted for robbery partly on the basis of his CSLI. (Law enforcement tracked his every movement for 127 days.) He argued that, by accessing his CSLI without a warrant, the government had violated his Fourth Amendment right to be free from unreasonable searches and seizures. Under the Supreme Court’s longstanding third-party doctrine, however, Carpenter didn’t seem to have a case: This doctrine holds that an individual loses his right to privacy in information he voluntarily turns over to a third party. (For instance, you have no privacy rights in business records that you turn over to a bank.) Carpenter argued that the third-party doctrine shouldn’t apply to CSLI, because it creates a comprehensive view of an individual’s life that far exceeds anything possible in the pre-digital age.
In an opinion by Chief Justice John Roberts, joined only by the liberal justices, the Supreme Court agreed. CSLI, Roberts explained, constitutes “a detailed chronicle of a person’s physical presence compiled every day, every moment, over several years.” This chronicle “implicates privacy concerns far beyond” what the court considered in earlier cases, when the government could only see your business records or the phone numbers you dialed on a landline. “In light of the deeply revealing nature of CSLI,” Roberts held, “its depth, breadth, and comprehensive reach, and the inescapable and automatic nature of its collection, the fact that such information is gathered by a third party does not make it any less deserving of Fourth Amendment protection.”
Having found that individuals have a “reasonable expectation of privacy” in their CSLI, and that “government access to cell-site records contravenes that expectation,” Roberts wrote that law enforcement must generally get a warrant—which requires probable cause of criminal activity—in order to access this “sensitive information.” From now on, the government may no longer show mere “reasonable grounds” for seeking CSLI; it must meet the much higher standards required for a warrant. On Friday, cell phone users in America regained their right to privacy “in the whole of their physical movements.”
Justices Kennedy, Thomas, Alito, and Gorsuch each wrote separate dissents, an unusual move that demonstrates their profound disagreement with the majority. Thomas and Gorsuch complained on originalist grounds, protesting that the court had moved beyond what the framers intended the Fourth Amendment to protect. Alito shared some of the majority’s concerns but fretted that the court had overreacted to new technology. Kennedy wrote that the court had “unhinge[d]” the Fourth Amendment “from the property-based concepts that have long grounded” its “analytical framework.” The dissents can all be summed up quite simply: Four justices believe you don’t deserve a right to privacy in information that you hand over to someone else, even if the only alternative is to throw away your cell phone.
The dissenters are right on one point, at least: Carpenter is an earthquake in Fourth Amendment law, modernizing the right to privacy for what Kennedy calls “the Cyber Age.” No longer will the court pretend that CSLI is indistinguishable from telephone numbers and bank records. It is, instead, a “qualitatively different category,” one that allows the government to glean an individual’s “familial, political, professional, religious, and sexual associations”—in short, the “privacies of life.” Finally, the court has moved beyond the rigid, doctrinaire application of anachronistic theories rooted in 18th-century property law and recognized the importance of applying ancient privacy principles to contemporary American life. The result is a historic and much-needed shift in constitutional law, one that provides vital new protections to the vast majority of Americans.