Yesterday, the 11th US Circuit Court of Appeals made a landmark decision regarding police access to cell phone tower tracking data. The Guardian is reporting by way of the Associated Press that, while ruling on the Miami armed robbery case of Quartavious Davis, a panel of three judges from the court decided that law enforcement officers must attain a judge’s warrant before seizing cell phone tower data that could be used to track a suspect’s movements. The ruling however was not used to overturn Davis’ conviction, as judges allowed a good faith exemption, since the ruling happened afterward, and law enforcement officers would not have been able to rely on it during the investigation.

Attorneys at various levels of government have long argued that individuals surrender their privacy rights by using a cell phone provided by a third-party company. However, consumer cell phone agreements respect users’ privacy in terms of the personal data stored through such services. The 11th US Circuit Court of Appeals ruled that warrantless cell phone tracking violates the Fourth Amendment, arguing that individuals have a reasonable expectation of privacy with regard to the details of their movements from place to place.

Cell phone tower data can be used to determine a significant amount of information about an individual. Details about one’s movements could be used to identify a person’s social relationships, business arrangements, religious beliefs, and other interests which are within the expectation of privacy. According to the ruling, law enforcement officers can attain such data during the course of an investigation, but only with a judge’s warrant after demonstrating probable cause.

This is the first time that a federal-level court has ruled on warrantless cell phone tracking in the context of a criminal case. The decision only applies to the 11th Circuit at the present time, which covers Alabama, Florida, and Georgia. A nationwide policy change would likely require a decision by the Supreme Court.

This follows the 2012 Supreme Court decision United States v. Jones in which justices ruled that the placement of a GPS device on an individual’s car is considered a type of search under the Fourth Amendment. The judges in the 11th US Circuit Court of Appeals referenced that decision in their comments on the case.

Law enforcement officers often seek cell phone tower data in an effort to determine whether or not a suspect was near the scene of a crime at the time that it was committed, as cell signals bounce off of nearby towers, leaving pings which constitute a “footprint” of the user’s movements. However, under this new ruling, investigators must acquire a personalized warrant from now on in order to attain such information in the states of Florida, Georgia, and Alabama.