In its June 2018 decision in Carpenter v. United States, the Supreme Court held that cell phone users have Fourth Amendment rights in their historical cell-site location records. Carpenter takes the Fourth Amendment in a new direction, adding new protections for non-content third-party business records. Carpenter prompts fundamental questions of what the Fourth Amendment means in the digital age. The Court is embarking on a new path. But what the new Fourth Amendment will look like, and what its limits may be, remain unclear.
This article is a discussion draft of two chapters from a book project, The Digital Fourth Amendment, forthcoming from Oxford University Press. The book argues that computers and the Internet should trigger new Fourth Amendment rules for the digital age. The facts of the digital world are different from the physical world, and new rules are needed to restore the role of the Fourth Amendment. The Supreme Court has already begun creating a Digital Fourth Amendment in Carpenter and its 2014 decision in Riley v. California. This book develops the rationale for the new rules, based on the theory of equilibrium-adjustment, and it offers a comprehensive picture of how the Fourth Amendment should apply to a wide range of doctrines.
The two chapters presented here offer a way to implement Carpenter. They develop and apply a test for Carpenter searches that is faithful to the decision, true to the theory of equilibrium-adjustment on which it rests, and yet also provides as much of the clarity that Fourth Amendment law demands as possible. Chapter 6, The Carpenter Shift, starts by explaining why Carpenter represents a departure from traditional Fourth Amendment principles based on a premature but explicit application of equilibrium-adjustment principles. It then argues that Carpenter should apply to Internet records when three requirements are met: The records exist because of the digital age, they are created without meaningful voluntary choice, and they tend to reveal the privacies of life. Chapter 7, Implementing Carpenter, explains that any records that satisfies these criteria should be protected. Courts should reject a mosaic theory that would limit Carpenter to long-term monitoring or case-by-case approaches that look to whether privacy invasions actually occurred. The Chapter ends by identifying specific examples of Internet records that should trigger Carpenter — and examples that should not.