It would "not be a search if you put a GPS device on all of our cars, monitored our movements for a month?" asked Chief Justice John G. Roberts Jr.
"The justices of this court?" Deputy Solicitor General Michael Dreeben said.
Yes, Roberts said.
"Under our theory and under this court's case, the justices of this court when driving on public roadways have no greater expectation -"
"So your answer is yes," Roberts interjected.
The chief justice said he understood the notion that agents could follow a person on foot or in a car, but "this seems dramatically different."
The new technology allows an agent to sit in an office and monitor the movements of many people, he said.
Justice Samuel A. Alito Jr. said he had the same concern. The "heart of the problem," he said, is that computers now permit the government to gather huge amounts of information on people and their activities. "Isn't there a real change" because of computers and surveillance technology? he asked.
It's "not a dramatic change," Dreeben said, in part because the government has no interest in tracking large numbers of citizens. He said the FBI used GPS devices sparingly to monitor suspicious people, including in terrorism cases.
But the justices kept returning to the same point. "Under the government's theory, any of us could be monitored whenever we leave home," said Justice Ruth Bader Ginsburg.
"If you win," said Justice Stephen G. Breyer, "it sounds like 1984" - a reference to George Orwell's novel about a futuristic state with total surveillance of the populace by the government.
Justices Antonin Scalia and Anthony M. Kennedy suggested they might opt for a ruling focusing on whether government agents could attach the GPS to a Jeep owned by Antoine Jones, a suspected drug dealer and the defendant in the case being considered.
"That seems to me a trespass," Scalia said.
But such a ruling would not decide the broad question of whether the government can use tracking technology to follow a person for weeks without first obtaining a warrant.
