The government argued on Friday that it should be allowed access to people's cell-phone records to help track suspected criminals.
A Justice Department attorney urged a federal appeals court to overturn lower court rulings denying it the right to seek information from communications companies about the call activity of specific numbers that authorities believe are associated with criminal activity.
But civil rights lawyers argued that providing information such as dates, times and call duration, and which cell towers the calls used, would be an invasion of privacy and a violation of constitutional protections against unjustified arrest.
Attorneys for the Electronic Frontier Foundation and the Center for Democracy and Technology said the government should have to obtain a warrant to track an individual via a cell phone and show probable cause that the information would provide evidence of a crime.
In 2008, the government asked for court permission to use cell phones for tracking without showing probable cause. The request was denied by a magistrate judge, whose decision was upheld by a district court. The government is appealing the lower court decisions before the U.S. Court of Appeals for the Third Circuit, which heard oral arguments on Friday.
The government is not seeking to monitor the content of cell phone conversations, said Mark Eckenwiler, an attorney for the Justice Department, but wants information on call activity to assist law-enforcement as it tracks suspected criminals.
Cell tower information is useful to law enforcement because of limited information it provides about the location of a cell phone when a call is made, the government said in a 2008 brief.
In February 2008, the government asked a lower court's permission to obtain from Sprint Spectrum the connection and cell-site information associated with a specific cell phone, on the grounds that it was relevant to an investigation on narcotics trafficking.
Kevin Bankston, an attorney for the Electronic Frontier Foundation, argued that cell tower data can allow officials to determine a cell phone user's location to within a tenth of a mile, and that could violate constitutional rights protecting a person from unreasonable seizure.
We think the data in this case is accurate enough to implicate the Fourth Amendment, he said.
Judge Dolores Sloviter, one of a three-judge panel, told Eckenwiler the government's case raised questions about the government's rights to track individuals.
There are governments in the world that would like to know where some of their people are or have been, she said, citing Iran as a government that monitors political meetings. Wouldn't the government find it useful if it could get that information without showing probable cause? Don't we have to be concerned about that?
The court is expected to rule in coming months.
(Editing by Michelle Nichols and Philip Barbara)