This past Wednesday, the US Court of Appeals for the Fourth Circuit ruled that police must first obtain a warrant before accessing mobile phone location data.
Extensive location data is accessible to the government through records of network provider companies. Every time a phone is used to transmit a call or a text message, the phone connects to the network's strongest--and likely, closest--station, and the network provider company maintains this data. This data, when assembled, can create a very detailed account of a person's movements for years. As Senior Judge Andre Davis stated, this "can enable the government to . . . discover the private activities and personal habits of the user."
Traditionally, data exposed to third parties such as phone companies has been accessible to the government without a warrant. According to the courts, when a person gives information to a third party, that person no longer has a legitimate expectation of privacy in that information. This enabled the government to access "pen registers"--lists of numbers dialed by a phone, recorded by the phone company--without a warrant.
However, as technology develops, data recorded by phone companies is far more extensive than a list of outgoing call numbers. Large amounts of data are stored automatically--locations, websites visited, e-mails, and text messages--and few customers assume that the phone company will actually access these records. Additionally, as some have argued, "it is nearly impossible to avoid disclosing the most personal of information to third-party service providers on a constant basis, just to navigate daily life." Allowing the government access to this private information without first requiring a demonstration of probable cause is an unacceptably high cost for everyday, necessary activities.
The Fourth Circuit opinion adapts the Fourth Amendment's protection of privacy to this development in technology. However, the Eleventh Circuit reached the opposite conclusion when confronted with the same issue, deciding that the government does not need a warrant to access mobile phone location data. This decision has been appealed to the United States Supreme Court. With at least two circuits reaching opposing conclusions on the issue, the Supreme Court may grant review to render a final decision on the matter.