The 'Smart' Fourth Amendment

“Smart” devices radiate data, detailing a continuous, intimate, and revealing pattern of daily life. Billions of sensors will soon collect data from smartphones, smart homes, smart cars, medical devices and an evolving assortment of consumer and commercial products. But, what are these data trails to the Fourth Amendment? Does data emanating from devices on or about our bodies, houses, things, and digital effects fall within the Fourth Amendment’s protection of “persons, homes, papers, or effects”? Does interception of this information violate a “reasonable expectation of privacy?” The “Internet of Things” and the growing proliferation of smart devices create new opportunities for police investigation. If this web of sensor surveillance falls outside of the Fourth Amendment, then warrantless collection and tracking of this smart data presents no constitutional concern. If these data trails deserve constitutional protection, a new theory of the Fourth Amendment must be developed. This article addresses the question of how the Fourth Amendment should protect “smart data.” It exposes the growing danger of sensor surveillance and the weakness of current Fourth Amendment doctrine. The article then suggests a new theory of “informational curtilage” to protect the data trails emerging from smart devices and reclaims the principle of “informational security” as the organizing framework for a digital Fourth Amendment.