Last week the Supreme Court heard arguments over whether police violated the Fourth Amendment protection against unreasonable search and seizure by tracking suspected drug dealer Antoine Jones 24 hours a day for four weeks in 2004, collecting data even after their search warrant expired. Jones’ lawyer argued the government should have to get a warrant anytime they want to place a GPS device on a car; the government argued it should never have to get a warrant no matter how long it tracks someone. It’s not a straightforward question.
Over the years, the courts have concluded that the police can tail a suspect in public without a warrant, can take his trash and search it once he puts it out on the curb and can use cameras to catch him running red lights or doing other illegal things in public spaces. But they need a warrant to search his home, listen in on his phone calls (except in a wide variety of circumscribed situations) or monitor him doing other things where Americans would have a reasonable expectation of privacy.
It very quickly became clear at the hearing last week that several of the justices in the center of the court thought the positions argued by both sides were extreme. The idea that the police could never track a car with GPS when they could tail it seemed not to make sense to Justice Kennedy, who asked if it would be unconstitutional for the police to collect the same information produced by the GPS by placing 30 deputies along Jones’ driving route.
But to Justices Roberts, Kagan and Breyer, there seemed to be a real difference in the amount of information the GPS could produce. Said Kagan:
[If] you think about a little robotic device following you around 24 hours a day anyplace you go that’s not your home, reporting in all your movements to the police, to investigative authorities, the notion that we don’t have an expectation of privacy in that, the notion that we don’t think that our privacy interests would be violated by this robotic device, I’m — I’m not sure how one can say that.
The intriguing idea Kagan and other justices seemed to be settling on, is that there’s a qualitative difference between the reasonableness of a search that produces a limited amount of data and a search that produces a huge amount, so much that an entirely different picture of a person begins to emerge. “You’re talking about the difference between seeing the little tile and seeing a mosaic,” Chief Justice John Roberts said, “The one gives you information, the other doesn’t.”
Big data, as the accumulation of vast databases on individual behavior is known, is a huge new area for business and for society generally. What protection should be provided by the courts vs. legislatures is also very much a new frontier (as always, Justice Scalia argued such protections are the province of lawmakers not judges, except when they’re not). Some lawmakers, like Ron Wyden have urged placing restrictions on the government’s use of databases.
But it will take someone with a broader perspective than a legislator or (probably) a judge to figure out what it means that a sufficiently large accumulation of data on an individual’s public behavior can constitute a breach of privacy.