Jacob Sullum on Warrantless Cellphone Tracking

In January the Supreme Court
unanimously ruled that tracking a suspect’s movements by
attaching a GPS transmitter to his car counts as a “search” under
the Fourth Amendment. But because the majority
opinion emphasized the physical intrusion needed to
surreptitiously install the transmitter, it did not resolve the
constitutional implications of surveillance using cellphones, the
tracking devices that Americans voluntarily carry in their pockets
and purses. In the absence of clear guidance, says Senior
Editor Jacob Sullum, law enforcement agencies are making up the
rules as they go along, often obtaining location data from
cellphone carriers without a warrant even for routine
investigations. Last week a House
subcommittee considered a bill that would address this
threat to privacy by requiring a warrant for geolocational
surveillance, regardless of the method used.