Award-Winning Paper: “The Many Revolutions of Carpenter”


For the tenth year, FPF’s annual Privacy Papers for Policymakers program is presenting to lawmakers and regulators award-winning research representing a diversity of perspectives. Among the papers to be honored at an event at the Hart Senate Office Building on February 6, 2020 is The Many Revolutions of Carpenter by Paul Ohm of Georgetown University Law Center. The paper’s detailed assessment of the 2018 Supreme Court opinion in Carpenter v. United States is an essential read for those interested in the changing conception of privacy in the criminal justice system.

The Supreme Court’s 2018 majority opinion in Carpenter v. United States, the author argues, is the most important Fourth Amendment opinion in decades. The opinion requires the police to obtain a warrant to access an individual’s historical whereabouts from the records of a cell phone provider.

Ohm states that Carpenter represents a new approach to the “reasonable expectation of privacy” test: “Until now, the Supreme Court has tended to pay more attention to the nature of the police intrusion required to obtain information than to the nature of the information obtained.” In Carpenter, the justices argued that individuals have a “reasonable expectation of privacy in the whole of their physical movements,” suggesting that data tracking those movements should be considered private and subject to warrant requirements.

Ohm notes that the Carpenter opinion serves as the death of the “third party doctrine” – an idea that holds that information a person voluntarily discloses to a third party is not protected by a reasonable expectation of privacy. The justices write: “the fact that the Government obtained the information from a third party does not overcome Carpenter’s claim to Fourth Amendment protection.” Ohm points out that the justices focused on the nature of the information rather than the structure of the database or its relation to the individual, likely ensuring that this opinion will apply to other massive collections of historical geolocation information.

Finally, Carpenter creates a previously unrecognized rule of “technological equivalence.” Ohm explains: “If a technology, or a near-future improvement, gives police the power to gather information that is the ‘modern-day equivalent’ of activity that has been held to be a Fourth Amendment search, the use of that technology is also a search.” The justices acknowledge that information technology is exceptional – different in kind, not merely in degree, from what has come before.

If you’re interested in reading more about how Carpenter v. United States represents an inflection point in Fourth Amendment court cases concerning privacy, you’ll want to check out the full paper.

The Privacy Papers for Policymakers project’s goal is to put diverse academic perspectives in front of policymakers to inform the development of privacy legislation. You can view all of this year’s award-winning papers on the FPF website.