The US Supreme Court has unanimously ruled that police needed a warrant to track a suspect with a GPS system on his car.
In 2005 police attached a GPS tracking device to a jeep driven by suspect Antoine Jones and used evidence from the device to show he was driving around distributing cocaine.
Jones appealed his conviction on the grounds that the police needed a warrant to place the device, and accordingly needed probable cause (and it seems in this case it would have been easy to show).
The main ruling was (in perhaps a shock to liberals) written by Justice Scalia who wrote
“Where, as here, the government obtains information by physically intruding on a constitutionally protected area, such a search has undoubtedly occurred.”
Justices Roberts, Kennedy, Thomas and Sotomayor agreed with Scalia while the remaining justices supported the view of Justice Alito, who limited the ruling to this specific case rather than establishing a broader rule. He also based his ruling on privacy grounds rather than 4th amendment grounds.
I tend to agree with Scalia that this was a clear 4th amendment issue but the fact we got a unanimous court on this issue is a good thing.