Abstract
Data aggregation has played a role in several recent cases implicating one’s reasonable expectation of privacy under the Fourth Amendment. Although the cases involved disparate doctrines, they all relied on data aggregation to depart from pre-existing Fourth Amendment jurisprudence. This essay considers where the aggregation principle will take us next. After referencing the emerging debates over cell site location information, the essay considers the implications of the aggregation principle for the following types of surveillance practices: short-term, individualized location tracking; short-term but large-scale location tracking; future location tracking technologies; and the aggregation of non-location information such as communications metadata.