This paper describes how the U.S. Supreme Court’s 2018 decision in Carpenter v. United States has the potential to usher in a new era of Fourth Amendment law. In Carpenter, the Court considered how the Fourth Amendment applies to location data generated when cell phones connect to nearby cell towers. The Court ultimately held that when the government demanded seven days of location information from defendant Timothy Carpenter’s cell phone provider without a warrant, it violated the Fourth Amendment. The decision sits at the intersection of two lines of cases: those that examine location tracking technologies, like beepers or the Global Positioning System (GPS), and those that discuss what expectation of privacy is reasonable for information disclosed to third parties, like banks or phone companies. In reaching its conclusion that a warrant was required, the Court upended existing precedent, ruling for the first time that location information maintained by a third party was protected by the Fourth Amendment.
In exploring the Court’s decision in Carpenter and its application to data from a variety of technologies — such as GPS, automated license plate readers (ALPRs), and wearables — this paper argues that it is incumbent on courts to preserve the balance of power between the people and the government as enshrined in the Fourth Amendment, which was intended to “place obstacles in the way of a too permeating police surveillance.” Moreover, in determining the scope of the Constitution’s protections for data generated by digital technologies, courts should weigh the five factors considered in Carpenter: the intimacy and comprehensiveness of the data, the expense of obtaining it, the retrospective window that it offers to law enforcement, and whether it was truly shared voluntarily with a third party. Section I is an overview of Fourth Amendment jurisprudence. Section II discusses the Carpenter decision and its takeaways. Section III applies Carpenter to various surveillance technologies and looks ahead at how Fourth Amendment jurisprudence might continue to develop in the digital age.