Should law enforcement agents have to obtain a warrant based on probable cause to attach a GPS tracker to a vehicle and track its movements? Several months ago we asked the Third Circuit Court of Appeals to consider our argument that they should (you can read our amicus brief here). Today, we will be in court arguing that point in the case of Harry, Mark, and Michael Katzin.

In 2010, hoping to confirm their suspicion that the Katzins had robbed a number of Rite-Aid pharmacies, FBI agents attached a GPS tracker to Harry Katzin’s car to track its movements. The agents did not seek a warrant from a judge before attaching the GPS device. They used the tracker to follow the Katzins as they drove to and from another Rite-Aid, and then arrested them shortly afterwards.

Last year the Supreme Court unanimously decided that attaching a GPS device to a vehicle and tracking it constitutes a “search” under the Fourth Amendment, but the Court did not address whether law enforcement needs a warrant before conducting GPS tracking. Today, we will argue that the government cannot engage in this type of tracking without going to a judge for a warrant first, since warrantless searches are unreasonable under the Fourth Amendment unless they fall within one of the few limited exceptions to the warrant requirement. In this case, the government claims the “automobile exception” applies, but that exception was created to ensure that contraband concealed in cars would not escape detection, not to permit tracking of individuals. The automobile exception was also created because of the practical difficulty of securing a warrant before the car drives away, and that purpose for the exception also does not apply to GPS tracking.

Warrants are essential because, as the Supreme Court has written, they provide “the detached scrutiny of a neutral magistrate, which is a more reliable safeguard against improper searches than the hurried judgment of a law enforcement officer engaged in the often competitive enterprise of ferreting out crime.” This safeguard is particularly important when it comes to GPS tracking because the technology is cheap, convenient, difficult to detect, and highly intrusive. Given how easy and inexpensive it is to track a suspect using GPS, neither cost nor effort will stop the government from using it in cases where it isn’t reasonable. The courts must impose strict limitations on the use of this technology in order to protect the right of all Americans to go about their daily lives without being tracked by the government. Essential elements of our privacy are at stake: as the D.C. Circuit Court of Appeals has explained,