Cell-site location data has become a popular tracking tool for law enforcement.  It is not as popular in the courts, however, which are split on whether a warrant is required to obtain such data.  Adding to the split, the Eleventh Circuit last week held, in United States v. Davis, that the government needs a warrant since a cell-phone user has a reasonable expectation of privacy in such data ? despite the fact that the data was conveyed to a third party, the mobile service provider.  Although the “third-party doctrine” has often been applied by courts to permit the government to obtain data entrusted to a third party without a warrant, several Supreme Court justices have suggested that the doctrine should be reconsidered when it comes to digital data.  The Eleventh Circuit is one in a line of lower courts that have done just that.