Yesterday the Supreme Court ruled on United States vs. Jones [PDF of court opinion], a case in which the FBI/DC police placed a GPS tracking device on the Jeep Cherokee of Antoine Jones, a club owner in DC who was suspected of dealing cocaine. The cops tracked Mr. Jones for 28 days, and, based on that evidence (as well as a CCTV camera pointing at the club door, a pen register (*) and a wiretap on Jones’s cellphone), charged him with conspiracy and possession with intent. Jones appealed, saying that the GPS data should be inadmissible since it was collected without a warrant.

The Supreme Court held up the ruling of the DC Court of Appeals in a unanimous 9-0 decision, saying that a) this was a search b) a car is a person’s property, or “effects”, and thus affixing a GPS to the undercarriage of the car violates the Fourth Amendment. From the ruling:

It is important to be clear about what occurred in this case: The Government physically occupied private property for the purpose of obtaining information. 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.

What’s interesting here is that there was a 5-4 split on why the Justices ruled as they did. Justice Sotomayor, writing a concurrent opinion, wrote, “When the Government physically invades personal property to gather information, a search occurs.The reaffirmation of that principle suffices to decide this case.” Since the government had invaded property, the Justices did not need to evaluate any of the other principles that this case brings up.

And there are many principles that this case brings up. Sotomayor talks about many of them: what about electronic surveillance if no property was trespassed upon? What about the chilling effects of potential long-term electronic surveillance? What about the fact that GPS monitoring gives far more specific information, and is far easier and cheaper, than traditional visual surveillance? What about the fact that this data can be stored and mined later? She writes:

I would take these attributes of GPS monitoring into account when considering the existence of a reasonable societal expectation of privacy in the sum of one’s public movements. I would ask whether people reasonably expect that their movements will be recorded and aggregated in a manner that enables the Government to ascertain, more or less at will, their political and religious beliefs, sexual habits, and so on. I do not regard as dispositive the fact that the Government might obtain the fruits of GPS monitoring through lawful conventional surveillance techniques… I would also consider the appropriateness of entrusting to the Executive, in the absence of any oversight from a coordinate branch, a tool so amenable to misuse, especially in light of the Fourth Amendment’s goa lto curb arbitrary exercises of police power to and prevent “a too permeating police surveillance.”

But most awesomely, Sotomayor then goes on to critique the third party doctrine. This says that if you disclose information to a third party (whether that’s your sister, Google, or Ma Bell), you have no reasonable expectation of privacy governing that information, and the government has a right to access it. As Sotomayor writes, “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” like checking email, signing up for Facebook, or buying a pair of shoes online.

In a concurring opinion, four other judges agreed with the majority ruling, but not the use of the property doctrine to decide it. Instead, Alito, Ginsberg, Breyer and Kagan seem suspicious of electronic surveillance overall. In Alito’s concurring judgment, he mentions GPS, road CCTV cameras, electronic toll collectors, and, most interestingly, cell phone location data as potential invasions of privacy. He laments that Congress and state governments have done little or nothing to regulate the use of this data by law enforcement.

I think the SCOTUS is itching for a fight on digital privacy. I’m looking forward to seeing what happens with similar cases in the future.

* Don’t get me started on pen registers. They track what numbers you call, and have the technical capability to track where your cellphone is and even your text messages. Yet the standard for ordering one is much lower than, say, wiretapping; the potential surveillee just has to be part of an ‘ongoing criminal investigation.’ Even more worryingly, Chris Soghoian has documented that law enforcement makes tens of thousands of requests to phone companies for cell phone location information. Requests to internet companies for location information are not even subject to the pen register standard; all they need is a subpoena.