A Unified Theory of Knowing Exposure: Reconciling Katz and Carpenter

Luiza M. Leão

The search doctrine has long been in a state of disarray. Fragmented into different sub-doctrines, Fourth Amendment standards of constitutional protection vary based on how the government acquires the information in question and on how courts define the search that occurred. As trespass-based searches, reasonable expectation of privacy searches, consent-based searches, third-party searches, and private searches each trigger different levels of protection, the doctrine has become what more than one Justice has termed a “crazy quilt.” This Note argues that unriddling the Fourth Amendment is easier than it might appear with the aid of the concept of knowing exposure, first discussed in Katz v. United States. An undercurrent across different strands of the search doctrine, the knowing exposure principle holds that what one “knowingly exposes to the public” is beyond the scope of Fourth Amendment protection. As the Court grapples with the search doc- trine in an age of unprecedented exposure to third parties, most recently in Carpenter v. United States, it should seek to unify the standard for searches around the foundational question of what renders one’s exposure “knowing.” Turning to Carpenter’s modifications to the third-party doctrine, this Note suggests a unified theory of knowing exposure that can apply across different kinds of searches, centering on whether the exposure is (1) knowing, (2) voluntary, and (3) reasonable.