Two leading civil liberties groups, the Electronic Frontier Foundation (EFF) and the American Civil Liberties Union, have intervened in a pending case in federal appeals court in Washington, DC. The two groups have filed an amicus brief urging the court to reject as unconstitutional the surreptitious placement, without a search warrant, of Global Positioning Service (GPS) devices by law enforcement on vehicles belonging to suspected criminals. Doing so without a warrant based on probable cause violates the Fourth Amendment's guarantees against unreasonable searches and seizures, the groups argued.

The brief was filed in US v. Jones, in which Lawrence Maynard and Antoine Jones were investigated by police for supposed cocaine trafficking. During the investigation, police placed a GPS device in Jones' vehicle, as well as surveilling the pair and targeting them with informants. They were ultimately arrested, and authorities seized 200 pounds of cocaine, a pound of crack cocaine, and $850,000 cash. Jones appealed, arguing that placement of a GPS device on his vehicle without a warrant violated his Fourth Amendment rights.

"The Supreme Court has recognized that a Fourth Amendment search may occur through the use of advanced technology to reveal detailed and personal information about individuals," the joint brief said. "These characteristics apply to GPS tracking, and a warrant should therefore be required for its unconsented use. Such a ruling also comports with the public's rejection of 'Big Brother' police surveillance, and with the empirical evidence that Americans have a strong expectation of privacy that their every movement by automobile or foot will not remotely be tracked or recorded by private parties or law enforcement."

The EFF and ACLU noted that the federal courts have previously placed limits on the use of new technologies to obtain information without a warrant. The US Supreme Court, for example, barred the use of thermal imaging of a person's home without a warrant.

The groups also argued that warrantless GPS tracking could undermine First Amendment rights to associate privately with others by allowing the government to track their whereabouts without their knowledge. "GPS tracking can reveal whether a person visits a Planned Parenthood clinic, patronizes a gay bar, or attends a meeting of an unpopular political organization," the brief states.

The groups also warned that GPS devices are growing more sophisticated and more versatile. Some GPS devices now work indoors, while others take the form of darts that can be fired at fleeing vehicles. "In sum, warrantless, remote GPS tracking trespasses on individuals' reasonable expectation not to be tracked electronically, twenty-four hours a day, for extensive periods of time," the brief concluded.