The Fourth Amendment, CSLI Tracking, and the Mosaic Theory

March 31, 2017


Law enforcement officials and privacy advocates have long clashed over the police’s ability to access and use information related to cell phones during criminal investigations. From wiretapping to physical searches of phones, the competing investigatory and privacy interests continue to battle for priority on a number of different fronts. This Note addresses the disagreement between academic scholarship and federal circuit courts over the proper resolution to one particular issue: cell site location information (CSLI).

CSLI refers to the records kept by a cellular service provider indicating the approximate location of a customer’s phone over time. Police often procure CSLI from providers to track a suspect’s movements in relation to criminal activity. However, when they do so without a warrant, courts are forced to determine whether the police violated the suspect’s Fourth Amendment right against unreasonable searches.

To date, all of the circuit courts to address this issue have held that warrantless CSLI monitoring is permitted under the Fourth Amendment. Many scholars, however, argue to the contrary, criticizing these decisions and creating a rift between the academic and judicial treatment of CSLI.

This Note explores the CSLI debate by analyzing the circuit courts’ decisions, scholars’ disagreement with those decisions, and the alternative approaches offered to protect and evaluate CSLI records. This Note concludes that warrantless CSLI monitoring should be analyzed under the “mosaic theory” of the Fourth Amendment. In support, it argues that this theory best addresses the concerns with CSLI tracking and proposes a standard that courts may use to apply it.

April 2017

No. 5