[co-author: Sophie Baum]*

In a landmark 5-4 decision, the United States Supreme Court held that the government conducts a search under the Fourth Amendment and therefore, absent exigent circumstances, needs a warrant supported by probable cause when obtaining cell-site location information (CSLI) (i.e., records of the cell towers to which mobile devices connect). The majority reached that conclusion based on the determination that such location records are subject to a reasonable expectation of privacy that continues to apply even though the location records are disclosed to the cell phone user’s wireless carrier, a third party.

The Court focused on the unique nature of CSLI. The Court noted that “seismic shifts in digital technology” have made it possible to track all cellphone users “for years and years,” and that these location records are “detailed, encyclopedic, and effortlessly compiled,” providing police with “access to a category of information otherwise unknowable.” According to the Court, cell phone tracking, like GPS monitoring, “is remarkably easy, cheap, and efficient compared to traditional investigative tools.” Relying on prior case law holding that “individuals have a reasonable expectation of privacy in the whole of their physical movements,” the Court concluded that individuals have a reasonable expectation of privacy in certain CSLI records.

The Court decision is significant in that, along with the holding that CSLI is subject to a reasonable expectation of privacy, the Court held that the “third-party doctrine,” which the Court has used in various contexts to conclude that individuals do not have a reasonable expectation of privacy in information disclosed to third parties, does not apply to the disclosure of CSLI to wireless carriers. The Court distinguished CSLI disclosures from other disclosures to service providers (e.g., when consumers disclose information to banks or dial telephone numbers), noting that mobile users do not voluntarily disclose CSLI to mobile carriers in the same ways that customers disclose records to other service providers. CSLI information is generated by virtually any mobile activity, “without any affirmative act on the part of the user beyond powering up.”

The opinion expressly states that the ruling applies only to historical CSLI records for periods of at least seven days. A different conclusion might be warranted for CSLI records covering shorter periods of time.

Though the Court was addressing law enforcement access to and use of historical CSLI, the ruling may have broader implications for businesses that collect consumers’ location data in various contexts. Certain claims that plaintiffs’ attorneys and consumer protection authorities may bring against companies, such as claims alleging invasions of privacy, incorporate a reasonable expectation of privacy standard. The Supreme Court’s Fourth Amendment jurisprudence influences the interpretation of that standard.

*Sophie Baum, in our Washington, D.C. office, contributed to this post.

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