Whose Line Is It Anyway? Probable Cause and Historical Cell Site Data

"For the Fourth Amendment protects people, not places. What a person knowingly exposes to the public, even in his own home or office, is not a subject of Fourth Amendment protection. But what he seeks to preserve as private, even in an area accessible to the public, may be constitutionally protected. " --Justice Potter Stewart (1) INTRODUCTION In most contexts, the Supreme Court has treated warrantless searches as presumptively unreasonable under the Fourth Amendment. (2) A prosecutor can rebut this presumption by demonstrating that the search or seizure was reasonable, meaning the state bears the burden of validating the warrantless search under one of the narrowly defined warrant requirement exceptions. (3) While a warrantless search of a home is presumptively unreasonable, (4) the Fourth Amendment's protection has not been extended to require a warrant to obtain a cell phone's location information. Privacy scholars have argued considerably over what showing the government must make in order to require cell phone providers to turn over the cell phone location information data they store. (5) During the summer of 2014, the Eleventh Circuit split with the Fifth and Third Circuits on whether the government must show probable cause to retrieve historic cell site data from cell phone providers in order to confirm that a suspect was close to where a crime was committed. The Fifth and Third Circuits have held that probable cause is not required to retrieve such information, but the Eleventh Circuit held the opposite in United States v. Davis. (6) Some commentators have suggested this was a questionable interpretation of the Fourth Amendment. (7) Historical cell site data is retrieved from a process whereby the cell phone communicates with the service towers nearby, and the process continues so long as the phone is powered on. (8) As the cell phone user moves away from one tower and approaches another, the phone will re-register at the closer tower. (9) Monitoring these tower switches can "map the movements of particular cell phones, and, consequently, their users." (10) Following the decisions in the courts of appeals, a unanimous Supreme Court held in Riley v. California (11) that the Fourth Amendment protects the contents of a cell phone from seizure without probable cause. (12) But Riley does not adequately resolve the issue of historical cell site data retrieval because obtaining the contents of a cell phone is distinct from knowing the phone's physical locations. (13) Even though the Riley decision does not reconcile the circuit split directly, it appears at least to support the Eleventh Circuit's effort to exclude cell phone data obtained without a warrant. Notwithstanding Riley, the Eleventh Circuit vacated its decision in September 2014 and has decided to rehear United States v. Davis en banc, revealing the importance and controversial nature of this issue. (14) The Fourth Circuit will consider the same issue on appeal after the district court's decision in United States v. Graham, (15) in which the lower court held that information voluntarily disclosed to a third party, i.e., the cell phone company, ceases to enjoy Fourth Amendment protection. This theory of disclosure to third parties is known as the third-party doctrine. (16) The third-party doctrine takes the view that under the Fourth Amendment, an individual "assume [s] the risk" that information will be disclosed to law enforcement when a person conveys that information to the third party. (17) While the view of the Fifth and Third Circuits is still the majority rule, it is an open question whether improvements in technology have caused the public's understanding of a reasonable expectation of privacy to evolve. Although some judges may not favor allowing the retrieval of cell phone location information without probable cause, their hands may be tied by the law as it stands, unless Congress is moved to act. …