What if there was a way for law enforcement to track suspects fleeing crime scenes in cars without the danger of a high speed pursuit that could put suspects, officers, and civilians at risk? One company claims to have just the solution. Is it legal?

Over the past few years, companies like Starchase have begun developing technologies like its “GPS bullet” pursuit management system, which the company describes as a “real-time tagging and tracking tool to reduce dangerous high-speed pursuits.”

The Starchase system can be mounted to the front-grill of police cruisers, and it fires stick-on “GPS bullets” or tracking devices at the suspect's vehicle through a compressed-air launcher. “The dispatcher then views the location and movements of the tagged vehicle in near real-time on a digital roadmap via a secure Internet connection,” thus rendering a dangerous high speed car-chase unnecessary. The system is being tested by a number of police departments around the US.

High speed car chases, often associated with action movie franchises like the Fast and the Furious and Die Hard, are, in fact, quite pervasive in the real world. Unlike Bruce Willis’s fictional Detective John McClane, most ordinary humans are not very durable. In fact, one study, undertaken in 2006, estimated that police pursuits have been causing “14,000 injuries and 700 pursuit deaths each year.”

Additionally, while a number of new investigative technologies like license-plate readers and law enforcement drones have drawn the ire of some civil libertarians, GPS bullet technologies (when used properly) do not appear to have quite as many downsides.

“We would not object to the GPS bullet technology when used in an exigent circumstance where an officer has probable cause," Jay Stanley of the American Civil Liberties Union told Ars. "But any other uses of GPS tracking technology outside the heat of a chase should require a warrant."

Such technologies have "the potential to obviate the need for high-speed pursuits by police cars through cities and towns, which are very dangerous and kill hundreds each year, with a third or more of those fatalities being innocent bystanders,” Stanley has further explained.

A silver bullet?

In the landmark 2012 decision in US v. Jones, the Supreme Court held that police violated the Fourth Amendment rule against unreasonable search and seizure when they attached a GPS device to a suspect's car and tracked it for 28 days without a warrant.

In Jones, a five-judge majority focused on the physical trespass involved in attaching the device to the car. "The Government physically occupied private property for the purpose of obtaining information," Justice Scalia wrote. "We have no doubt that such a physical intrusion would have been considered a 'search' within the meaning of the Fourth Amendment when it was adopted."

While the case of GPS bullets and the Starchase system sounds quite similar to the issue in Jones, Matthew Meyers, in his recent law review article titled “GPS ‘Bullets’ and the Fourth Amendment,” argues that the two situations are not analogous from a legal perspective. Meyers explains that, when used properly, the placement of GPS bullets on a suspect’s car can be distinguishable from the continuous GPS trackers at issue in Jones.

In a phone interview with Ars, Meyers said that when officers are actively pursuing a suspect for whom they have established probable cause, they need not obtain a judicial warrant before placing a GPS bullet on the suspect’s car, even though this physical placement constitutes a “trespass” and “search” under Jones.

This is because, according to Meyers, a high speed car chase is a quintessential “exigent circumstance” scenario for which the Fourth Amendment provides an exception to the warrant requirement.

“Officers may engage in a search that would otherwise violate the Fourth Amendment when there is a sufficient exigency warranting the search… A police pursuit by car is a paradigmatic case of an exigent circumstance justifying a warrantless search,” Meyers explains in his article. He continues, “The exigency of a police pursuit would excuse the otherwise unlawful search with the GPS Bullet.”

A gateway technology

Meyers and Stanley both argue that GPS bullet technologies can be a lawful policing method to stave off a dangerous high speed car chase when applied in exigent circumstances where probable cause has been established. However, both caution against broad applications of such technologies.

Meyers told Ars:

There is a real fear as a policy matter that this kind of technology could open some doors to abusive police practices. For instance, what if the guy running away has a cellphone that the police could tap into quickly. That's the really open question that wasn't answered by Jones. If we allow technologies like GPS bullets, this might open the doors to the police being able to, for example, tap his cellphone directly to locate him absent a warrant.

Stanley voiced similar concerns. “Emergency exceptions are invoked all too often by law enforcement officers." As a result, he recommends that police limit the situations where they can invoke this specific exception by requiring removal of the tracking device once the police catch up to the person they are chasing. He also explains that officers should be required to make every effort to catch the suspect as soon as possible, so as to not allow for an extended search period.

For now, this technology remains squarely in the testing stage. No such limits have been formally implemented or publicly discussed by law makers.