Cell phones are miniature radio transmitters that constantly broadcast their location even when no call is in progress.
The FBI and other police agencies often seek access to that location-tracking information, which displays the cell phone owner's movements in real time. But only now are judges beginning to scrutinize what have traditionally been routine tracking requests--and concluding that police must show at least some evidence of actual criminal activity.
Police blotter was the first to report last month that a federal judge had blocked a Justice Department's eavesdropping request. Since then, two subsequent court decisions also have rejected police surveillance procedures aimed at monitoring the location of cell phone users.