Location Tracking and Digital Data: Can Carpenter Build a Stable Privacy Doctrine?

2019 Supreme Court Review, Forthcoming

U of Michigan Public Law Research Paper No. 626

53 Pages Posted: 4 Jan 2019 Last revised: 16 Jan 2019

See all articles by Evan Caminker

Evan Caminker

University of Michigan Law School

Date Written: December 20, 2018


In Carpenter v. United States, the Supreme Court struggled to modernize search and seizure law for the digital age. Under longstanding doctrine, government needs only a subpoena rather than search warrant to obtain phone, financial, credit card, and many other types of records from “third party” businesses. And exploding use of the internet and other digital technologies has drastically increased the amount and types of sensitive information stored by third parties that reveal people’s movements and activities. Acknowledging this concern, the Court held in Carpenter that government needs a warrant to obtain a week’s worth of wireless carrier’s cell-site records showing a cell phone’s approximate location. The Court embraced for the first time a “mosaic” view of privacy intrusions, stressed the special sensitivity of detailed location information, and found cell phone use to be necessary today rather than voluntary. The Court stressed that its holding is narrow, emphasizing that location information is “qualitatively different” from other third-party records. But the Court’s reasoning is potentially quite expansive, and many privacy advocates downplay the cautionary prose and hail the decision as game-changing.

Carpenter’s result, while requiring aggressive depiction of facts and reshaping of precedent, is not surprising ― the notion that government can cheaply and easily track our movements naturally stirs anxieties about Big Brother. But whether the Court’s reasoning ought to and will extend to other types of third-party information is far from clear. And the Court’s explanation for requiring a warrant may affect other types of subpoenas as well. In this Article I carefully evaluate the Court’s reasoning, tease out possible and likely implications of both the search and reasonableness rulings, and ultimately suggest that Carpenter more likely reflects a strong first step towards a new privacy‒law enforcement equilibrium rather than a consciously radical regime change.

Keywords: Carpenter, reasonable expectation of privacy, third-party doctrine, warrant, subpoena

Suggested Citation

Caminker, Evan H., Location Tracking and Digital Data: Can Carpenter Build a Stable Privacy Doctrine? (December 20, 2018). 2019 Supreme Court Review, Forthcoming, U of Michigan Public Law Research Paper No. 626, Available at SSRN: https://ssrn.com/abstract=3304775

Evan H. Caminker (Contact Author)

University of Michigan Law School ( email )

625 South State Street
Ann Arbor, MI 48109-1215
United States
734-763-5221 (Phone)
734-763-9375 (Fax)

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