Mass. Supreme Judicial Court Rules Two Days of Mass Transit Records Not Enough to Constitute Search Under Fourth Amendment Mosaic Theory

August 5, 2021

The Massachusetts Supreme Judicial Court issued an opinion in Commonwealth v. Zachary finding that when Boston Police accessed two days of rider history from a metro pass they did not perform a search under the Fourth Amendment. The court first followed an argument from EPIC’s amicus brief urging the court to reject the third-party doctrine for electronic data collected by a third party from an individual for the purpose of obtaining a service. The court decided, “we reject the doctrine as applied to this case, where the data at issue has no connection to the limited purpose for which an individual uses a CharlieCard.” The court then applied the mosaic theory of the Fourth Amendment which looks at the whole sweep of a government action and the insights derived when individual data points are aggregated to determine whether a search occurred under the Constitution. The court held that while “an extensive record of an individual’s MBTA activity could constitute a search under the mosaic theory, the minimal amount of data obtained in this case does not constitute a violation of art. 14 or the Fourth Amendment.” EPIC previously filed an amicus brief in the landmark location privacy case Carpenter v. United States, in which the Supreme Court held that collecting seven days of cell phone location data, considered in aggregate, constituted a search.

Support Our Work

EPIC's work is funded by the support of individuals like you, who allow us to continue to protect privacy, open government, and democratic values in the information age.