Last January, the US Supreme Court ruled that the police must obtain a warrant before secretly attaching a GPS tracking device to your car, at least for any length of time. The decision in Jones v. United States was heralded as a small victory for those of us who like our gadgets but love our privacy even more.

Yesterday, the US Circuit Court of Appeals for the Sixth Circuit failed to uphold the same kind of privacy protection for cell phones. In United States v. Skinner it ruled that because we all know cell phones have GPS transponders that can broadcast our locations at any time, we have no reasonable expectation of privacy when we carry them.

[Want to Track Someone's Car? More Options Roll Out]

(Disclaimer: I am not a lawyer. And not only am I not a lawyer, but reading legal arguments makes me want to lie down with a cool towel over my head until the throbbing goes away. So take this blog entry with a grain of salt and two Advils, and call an attorney in the morning.)

Ars Technica nicely summarizes the facts of the case. It concerns a dope smuggler named Melvin Skinner (aka “Big Foot”). Old Big Foot was part of a ring of marijuana distributors that used disposable cell phones (aka “burners”) to coordinate their activities (apparently, they too were big fans of The Wire). Big Foot was arrested by the cops at a rest stop in Abilene, Texas, driving a motorhome filled with more than half a ton of marijuana. The cops found him via the location data provided by his cell phone.

The police did obtain legal authority to obtain Bigfoot’s cell phone data – what are known as pen register/trap trace orders. So they could find out who he called and when he called them, but they weren’t able to listen in on his conversations. The legal question was whether his location data fell under the legal definition of “stored communications,” which can be obtained fairly easily by the cops, or if it was a search under the Fourth Amendment, which requires more stringent judicial oversight.

Bigfoot’s lawyers argued that it was a search, and that the cops did not obtain a warrant sufficient to obtain that information. The court ruled it was just data, and thus covered under the trap trace. And since it involved a gadget the suspect was already carrying, there was no trespass on his property, a la Jones v. US.

The majority opinion by Judge John Rogers [PDF] is more than a bit disturbing, however. He wrote:

There is no Fourth Amendment violation because Skinner did not have a reasonable expectation of privacy in the data given off by his voluntarily procured pay-as-you-go cell phone. If a tool used to transport contraband gives off a signal that can be tracked for location, certainly the police can track the signal…. It follows that Skinner had no expectation of privacy in the context of this case, just as the driver of a getaway car has no expectation of privacy in the particular combination of colors of the car’s paint.

In case you missed that, Judge Rogers believes that cell phone location data is no more private than the color of your car. He also goes out of his way to note that “an innocent actor would similarly lack a reasonable expectation of privacy in the inherent external locatability of a tool that he or she bought.” So this doesn’t just apply to alleged drug smugglers; it applies to you and me as well.

Orin Kerr at The Volokh Conspiracy legal blog gets to the essential question: How did the cops obtain that location data, exactly? Did the wireless company that provided the burners periodically record the phone’s location, leaving a trail of breadcrumbs for the cops to follow? Or did the cops tell them to ping it? That would be more like being able to describe the paint on your car from a distance of several hundred miles. Is that something anyone should reasonably expect? I think not.

The question isn’t so much whether Big Foot is guilty; the question is whether the police treated his location data – and by extension, all of ours as well -- with the restraint dictated by the Fourth Amendment.

The way our system works is that if the cops want to violate my personal privacy, they need to a) have a pretty compelling reason, and b) convince a judge their reasons are compelling. If that Sixth District ruling stands, the cops will be able to follow anyone at any time for almost any reason, using the tools we bought and paid for. Does that seem right to you?

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This story, "Federal Judge: Your Location is No More Private Than the Color of Your Car" was originally published by ITworld .