You might think that if the US Supreme Court's ruling that a GPS device was a "search," the inevitable conclusion is that police would need a warrant to install a GPS device on a car.  After all, warrantless searches are per se unreasonable under the Fourth Amendment (except in few limited exceptions), so the absence of a warrant would make the search unconstitutional.

The government attorneys arguing United States v. Katzin must not have gotten that memo. But now, in an important new decision, the Third Circuit Court of Appeals ruled that, indeed, police need to get a probable cause search warrant in order to install and track a car's location with a GPS device.

In 2010, FBI agents installed a GPS device on a minivan without a search warrant to track the movements of the three Katzin brothers, who were suspected of committing a string of robberies. At the time they installed the GPS device, federal courts had reached differing results on whether the installation of a GPS device and the subsequent tracking was a "search" under the Fourth Amendment. If it is a search, that would require police to obtain a search warrant before using it. That question was put to rest when the Supreme Court issued its landmark 2012 decision in United States v. Jones, ruling that the installation of a GPS device to track a car was a "search" under the Fourth Amendment. 

After Jones was decided, the Katzins moved to suppress the GPS evidence obtained without a search warrant. The government argued that Jones only addressed the installation of a GPS device, not the subsequent tracking, and that a variety of exceptions to the Fourth Amendment authorized the warrantless tracking of the car. It also argued that officers reasonably relied on two Supreme Court cases from the 1980s—United States v. Knotts and United States v. Karo—which found no Fourth Amendment violation when police installed beepers inside a container to follow the suspects in public as they transported the containers around without a warrant. Generally, courts will not suppress evidence if the police rely on binding legal precedent in effect at the time they searched, even if that prior decision is later overruled or changed. The government's argument was that Knotts and Karo sanctioned the GPS tracking here.

The district court was unpersuaded, and suppressed the GPS evidence. The government then appealed to the Third Circuit, and we filed an amicus brief where we argued that Jones meant what it said and that police need a search warrant to both install and track a car with a GPS device. We also argued that Knotts and Karo couldn't authorize the more invasive location tracking that occurred here.

Thankfully, the Third Circuit agreed. In ruling that a search warrant was required, it rejected the government's arguments that the use of a GPS device was the equivalent of a stop and frisk under Terry v. Ohio or fell within the automobile or special needs exceptions to the search warrant requirement. Even more importantly, the Court found the officers could not reasonably rely on prior Supreme Court decisions involving more primitive technologies to justify their actions here. Noting "the marked technological differences between beepers and GPS trackers," it found Knotts and Karo didn't control and ultimately affirmed the lower court decision suppressing the evidence.

Katzin is an important decision and makes clear that police must use a search warrant to both install and track a person with a GPS device. But even more important is its handling of Knotts and Karo and specifically how the Court looked critically at older Supreme Court cases involving much more primitive surveillance to analyze the government's actions here.

The implications of that critical perspective are potentially major. Most notably, the government has repeatedly justified its electronic surveillance collection practices by citing Smith v. Maryland, a 1979 Supreme Court case finding that a person has no expectation of privacy in the phone numbers they dial. It has used Smith to support everything from the NSA's bulk collection of metadata to the FBI's warrantless acquisition of cell site records, and argued people have no expectation of privacy in information turned over to third parties. But the technology—and the consequences of using it—are vastly different today.

The Third Circuit got it right in noting that comparing beepers to GPS trackers is like comparing apples to oranges. We hope other courts reviewing the government's electronic evidence gathering follow the Third Circuit's lead, and instead of relying on faulty comparisons to outdated, less invasive technologies, review the surveillance for what it actually is.

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