Warrantless cellphone location tracking is illegal, US circuit court rules

A US Appellate Court has ruled that police must obtain a warrant before collecting cellphone location data, finding that acquiring records of what cell towers a phone connected to and when it was connected to them constitutes a Fourth Amendment search.

This ruling, from the 11th Circuit, is in opposition to a ruling made nearly a year ago by a separate appellate court. While this ruling won't overturn that one because of their separate jurisdictions, it adds critical precedent to a privacy question that's still far from decided across the country.

In its reasoning, the court notes that while the Fourth Amendment has traditionally been applied to property rights, it's gradually expanded to protect much more, including communications. "In the 20th century, a second view gradually developed," the court writes, "that is, that the Fourth Amendment guarantee protects the privacy rights of the people without respect to whether the alleged 'search' constituted a trespass against property rights."

In particular, the court cites a Supreme Court ruling that found that tracking a person using a GPS unit installed in their car requires a warrant. Even though the location data of a cell site can only place the person holding the phone within a certain range, the court feels that that range is still quite detailed. In the case at hand, cell site data was used to place the defendant near the location of several robberies.