Document Type


Publication Date

January 2017


Amici curiae are forty-two scholars engaged in significant research and/or teaching on criminal procedure and privacy law. This brief addresses issues that are within amici’s particular areas of scholarly expertise. They have a shared interest in clarifying the law of privacy in the digital era, and believe that a review of scholarly literature on the topic is helpful to answering the question in this case. This brief is co-authored by Harry Sandick, Kathrina Szymborski, & Jared Buszin of Patterson Belknap Webb & Tyler LLP.Carpenter v. United States presents an opportunity to reconsider the Fourth Amendment in the digital age. Cell phones are only one of the many new and pervasive digital technologies which automatically collect and reveal intimate personal data, such as Cell Site Location Information (“CSLI”), to third parties. This Amicus brief argues that the Supreme Court should resist extending the reasoning of Smith v. Maryland, 442 U.S. 735 (1979) — a 38-year-old case built on a faulty privacy premise — to the modern, hyper-connected, technology-dependent world. Instead, the Court should recognize that the new realities of this world require new legal doctrines to fit the privacy expectations shared by most Americans.Criminal procedure and privacy scholars are in near-unanimous agreement that an extension of what some have called the “third-party doctrine” could eliminate citizens’ privacy in the modern age. CSLI (and other data transmitted to third parties in the modern age) can reveal an individual’s interests, friendships, activities, travel, associations, beliefs, health concerns, financial problems, employment, and education. Smith is grounded in a pre-digital era, and cannot support future application of the Fourth Amendment. An extension of Smith’s reasoning would give law enforcement ever increasing access to the most private details of individuals’ lives without a warrant or probable cause. As a matter of Fourth Amendment practice, extending the third-party doctrine would curtail digital privacy and encourage arbitrary government intrusions into the lives of American citizens. As a matter of Fourth Amendment theory, applying the third-party doctrine to the digital world would undersell the value of privacy, and contradict the logic of Katz v. United States, 389 U.S. 347, 359 (1967). And, as a matter of precedent, Smith offers an inapposite and inadequate doctrinal foundation to support the future of a digital Fourth Amendment.