"Smart" devices radiate data, exposing a continuous, intimate, and revealing pattern of daily life. Billions of sensors 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 devices fall within the Fourth Amendment's protection of "persons, houses, papers, and effects"? Does interception of this information violate a "reasonable expectation of privacy"? 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.
