Why Supreme Court's GPS ruling will improve your privacy rights

The U.S. Supreme Court's sweeping decision requiring police to obtain search warrants to plant GPS tracking devices on automobiles will broadly enhance Americans' electronic privacy rights, legal experts predicted today.

This morning's unanimous ruling (PDF) says the customary law enforcement practice of installing GPS trackers without judicial approval--which has become more common as prices have fallen--violates Americans' Fourth Amendment rights to be free from warrantless searches.

That reasoning suggests police also need to obtain warrants before tracking the locations of cell phones and mobile devices, another contentious topic currently before the courts, said Greg Nojeim, an attorney at the Center for Democracy and Technology.

A careful look at the way the justices ruled today suggests that "a warrant would be required before cell phones could be turned into tracking devices," Nojeim said.

In 2005, CNET was the first to report that the Justice Department believed it did not need a warrant to track the location of cell phones. Government attorneys made the same argument before the Third Circuit Court of Appeals in Philadelphia in 2010, and another case is before the Fifth Circuit Court of Appeals in New Orleans.

Other forms of police surveillance done without a warrant, such as the increasingly common practice of using remotely controlled aerial drones to monitor citizens, also could be curbed.

If "drones are used to track people's movements, this decision could have an impact on that as well," says Catherine Crump, a staff attorney at the American Civil Liberties Union who specializes in privacy and technology.

And Marc Rotenberg, head of the Electronic Privacy Information Center, suggests that today's no-physical-tracking-without-warrant rule would apply to other forms of surveillance such as the tracking bugs that Gene Hackman and Will Smith immortalized in the movie Enemy of the State.

"That is not just cars," Rotenberg says. "It includes tags on coats and briefcases."

One justice, Sonia Sotomayor, went even further than her colleagues and suggested that the legal privacy standards for an electronic age, sometimes called the third-party doctrine, should be rethought:

More fundamentally, it may be necessary to reconsider the premise that an individual has no reasonable expectation of privacy in information voluntarily disclosed to third parties. This approach is ill suited to the digital age, in which people reveal a great deal of information about themselves to third parties in the course of carrying out mundane tasks. People disclose the phone numbers that they dial or text to their cellular providers; the URLs that they visit and the e-mail addresses with which they correspond to their Internet service providers; and the books, groceries, and medications they purchase to online retailers.

Muddying the waters is how fractured today's Supreme Court opinion is. While all nine justices agreed that a warrant was required for GPS tracking, they splintered into different groups that reached the conclusion through different chains of reasoning.

The opinion of the court, written by Justice Antonin Scalia, analyzed a 21st-century privacy issue by looking at how the Fourth Amendment was understood at the time it was adopted in the 18th century--and relying heavily on property rights. (A concurrence would have reached the same result by relying on whether Americans enjoy a reasonable expectation of privacy.)

"The government physically occupied private property for the purpose of obtaining information," 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."

Scalia said today's case did not require the court to address whether an electronic intrusion counts as a trespass that violates property rights: "It may be that achieving the same result through electronic means, without an accompanying trespass, is an unconstitutional invasion of privacy, but the present case does not require us to answer that question."

Today's GPS tracking case arose out of a criminal prosecution of Antoine Jones and Lawrence Maynard, two suspected cocaine dealers who ran a nightclub in Washington, D.C. Jones said the warrantless use of a GPS device to track every movement of his vehicle over the course of a month violated the Fourth Amendment, which generally says that warrantless searches are "unreasonable."

In August 2010, the U.S. Court of Appeals for the District of Columbia agreed (PDF), tossing out Jones' conviction "because it was obtained with evidence procured in violation of the Fourth Amendment."

"A reasonable person does not expect anyone to monitor and retain a record of every time he drives his car, including his origin, route, destination, and each place he stops and how long he stays there; rather, he expects each of those movements to remain 'disconnected and anonymous,'" circuit judge Douglas Ginsburg wrote.

Even though police are planting GPS bugs on Americans' vehicles thousands of times a year, the legal ground rules remain unclear, and lower courts had split on whether a warrant should be required. Once relegated, because of their cost, to the realm of what spy agencies could afford, GPS tracking devices now are readily available to jealous spouses, private investigators, and local police departments for just a few hundred dollars.

The Justice Department had argued (PDF) that no American has "a reasonable expectation of privacy in his movements from one place to another," even if technological advancements "allow police to observe this public information more efficiently."

As a response to law enforcement's aggressive use of warrantless tracking--the Los Angeles Police Department even has a dart it can fire at and implant in a passing car--legislation has been introduced in the U.S. Congress and state legislatures to require judicial oversight.

Last summer, Sen. Ron Wyden (D-Ore.) and Rep. Jason Chaffetz (R-Utah) introduced bills that would provide new legal protections for "geolocation information," meaning data that can locate a person through a wireless device or a GPS tracker placed on a vehicle.

California didn't wait for the Supreme Court: it enacted a law saying the use of "an electronic tracking device to determine the location or movement of a person" implicitly requires a warrant for police use of a GPS. A handful of other states have taken similar steps, enacting penalties for some uses of electronic tracking devices or excluding their evidence from criminal proceedings unless police obtain warrants.

Update: George Washington University law professor Orin Kerr argues that United States v. Jones, decided today, was a relatively narrow ruling.