Supreme Court limits police GPS tracking powers
The US Supreme Court has banned law enforcement officers from planting GPS tracking bugs on suspects' vehicles without a search warrant.
Officers will now have to seek permission from a judge before using such devices to monitor suspects.
The ruling could have an impact on the investigation of major crimes such as drug smuggling.
But it will be welcomed by civil liberties campaigners who have warned against unwarranted surveillance.
The Supreme Court considered the issue as part of the case against a suspected drug smuggler who was convicted after his car was tracked by GPS.
In 2005, FBI agents attached a tracking device to the underside of a Jeep Grand Cherokee, registered to the wife of Washington DC nightclub owner and suspected drug smuggler Antoine Jones.
He was then tracked for 28 days, and eventually sentenced to life in prison after the authorities used the device to link him to a suburban house used to stash money and drugs.
But that conviction was overturned by an appeal court because the officers did not have a search warrant when they attached the satellite tracking bug.
Jones's legal team argued at a Supreme Court hearing in November that his Fourth Amendment rights, which are meant to protect US citizens from invasive searches, were violated.
Lawyers for the Obama administration argued that Jones did not have a "legitimate expectation of privacy" - the standard legal test in the US for the past 45 years - because his car was in a public place.
Attaching a tracking device to it was no different to "tailing" him, which has always been legal, the government argued.
The Supreme Court disagreed and ruled that Mr Jones' Fourth Amendment rights had been violated.
But correspondents say the ruling is unlikely to have an impact on the use by law enforcement agencies of another surveillance method, mobile phone tracking software.