585 U.S. ___, 138 S. Ct. 2206, 201 L. Ed. 2d 507 (2018) (U.S. Supreme Court)
Carpenter v. United States is the Supreme Court's landmark decision adapting traditional Fourth Amendment doctrine to the realities of the digital age.
Does the government's acquisition of historical cell-site location information from a wireless carrier without a warrant supported by probable cause constitute a search under the Fourth Amendment?
An individual maintains a reasonable expectation of privacy in the record of his physical movements as captured through historical cell-site location information. Government acquisition of such CSLI from a wireless carrier is a Fourth Amendment search that generally requires a warrant supported by probable cause. The third‑party doctrine of Smith v. Maryland and United States v. Miller does not extend to the unique, deeply revealing, and involuntarily generated nature of CSLI. Traditional exceptions to the warrant requirement, including exigent circumstances, remain available, and the Court's holding is narrowly focused on historical CSLI rather than other forms of business records or real-time tracking.
Yes. Obtaining historical CSLI from a wireless carrier is a Fourth Amendment search. In the absence of an applicable exception, the government must secure a warrant supported by probable cause; an SCA § 2703(d) order is insufficient.
Carpenter is foundational for understanding how Fourth Amendment doctrine adapts to digital technologies. It limits the third‑party doctrine by recognizing a reasonable expectation of privacy in certain highly revealing data held by third parties, and it establishes that historical CSLI is protected information that generally requires a warrant. For students, the case is a critical node connecting Katz, Smith, Miller, Jones, and Riley, and it illustrates the Court's willingness to craft technology-sensitive rules while preserving traditional exceptions and leaving room for case-by-case development on related questions (real-time tracking, tower dumps, metadata categories, and national security contexts).