UPDATE: Supreme Court Takes Fourth Amendment Case about Cell Phone Location Data [June 26, 2018]   [open pdf - 399KB]

"Update: On June 22, 2018, the Supreme Court held in a 5-to-4 decision in Carpenter v. United States that government acquisition of historical cell site location information (CSLI) constitutes a Fourth Amendment search. The Court further held that the government needs a warrant supported by probable cause--not merely a court order under the Stored Communications Act--to acquire historical CSLI in most circumstances. The majority opinion, authored by Chief Justice Roberts and joined by Justices Ginsburg, Breyer, Sotomayor, and Kagan, concluded that 'an individual maintains a legitimate expectation of privacy in the record of his physical movements as captured through CSLI.' A central issue in the case concerned the viability of the Court's third-party doctrine, which generally recognizes that no reasonable expectation of privacy exists as to information that a person discloses voluntarily to third parties. The majority in Carpenter reasoned that the third-party doctrine, which developed in cases holding that individuals have no reasonable expectation of privacy in the telephone numbers that they dial or in financial records held by their banks, does not apply to CSLI, because '[t]here is a world of difference between the limited types of personal information addressed in [those cases] and the exhaustive chronicle of location information casually collected by wireless carriers today.' The Court recognized, however, that certain exceptions to the warrant requirement, including the exception for ongoing emergencies, remain in place and will likely allow law enforcement to obtain CSLI without a warrant in some circumstances."

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