As courts attempt to develop Fourth Amendment doctrine to address the threats to privacy created by digital surveillance technologies, a valuable doctrinal resource has been largely neglected: the law governing the seizure of persons. Just as courts today struggle with the specter of mass search using digital technologies, courts in the 1960s were confronted with the problem of mass seizure through the growing use of stop-and-frisk by police departments. The responses to mass seizure developed by the Supreme Court in Terry v. Ohio (1968) and its progeny provide lessons for courts today considering how to respond to the risks of digital mass search. By adopting the “mosaic theory,” the Supreme Court has already begun to apply to digital search a form of aggregative reasoning that has long been used to define the seizure of persons.
The analogy between seizure doctrine and search doctrine also sheds light on the significance of the Supreme Court’s recent, landmark decision in Carpenter v. United States (2018), which responded to the declining cost of digital surveillance in a way that resembles Terry’s response to the rising use of stop-and-frisk in the 1960s. Carpenter opens the door for courts to develop a two-tiered doctrinal scheme for digital search, with less invasive searches requiring reasonable suspicion and more invasive searches requiring probable cause. Among other virtues, such an approach would provide a doctrinal foothold for subjecting the bulk collection of metadata and other digital mass surveillance programs to Fourth Amendment review.