Should police be able to put GPS trackers on cars without a warrant?

Justices on the Supreme Court today expressed reservations about the Obama administration's argument in support of police surveillance teams placing hidden GPS devices on vehicles indefinitely without first obtaining a warrant.

Attorneys for convicted D.C.-area drug dealer Antoine Jones are arguing that the federal government overstepped its authority by conducting warrantless surveillance on Jones' car via concealed GPS trackers. (To get a warrant, agents must show there is probable cause to believe someone is committing a crime. In Jones' case, officers had obtained a warrant, but it had expired before they tagged his car.)

The government is arguing that people do not have a right to privacy while traveling on public roads. Police are allowed to physically follow people and even dig through their trash without a warrant, and the Obama administration says that the GPS technology amounts to the same surveillance method.

But some justices on the court seemed deeply skeptical of that line of reasoning.

"So . . . you could tomorrow decide that you put a GPS device on every one of our cars, follow us for a month; no problem under the Constitution?" Chief Justice John Roberts asked the government's lawyer, Michael Dreeben. Dreeben replied that yes, the justices could not expect privacy on public roads and the government would be within its rights to put GPS devices on their vehicles.

Justice Stephen Breyer said that the GPS trackers could not be compared to physical police surveillance, because the ease of the technology means that theoretically every single U.S. citizen could be followed at all times. By contrast, Breyer noted, the government would never have the resources to physically tail a large number of people. "So if you win, you suddenly produce what sounds like 1984," Breyer said.

As Forbes' Kashmir Hill writes, the justices' aggressive response in the oral arguments signals that they may write a broader ruling on the intersection of technology and privacy. The last Supreme Court ruling on electronic government surveillance was in 1983, and involved pagers.

Meanwhile, Wired's Kim Zetter tracked down a 25-year-old man named Greg in San Jose, California who recently discovered one of the feds' tracking devices on his car. Greg says he believes he's being tracked because his cousin, a Mexican citizen, fled over the border recently and may have been a drug dealer. The Justice Department wouldn't tell Wired whether the device belonged to its agents--or whether they were investigating Greg.