In United States v. Jones (2012), the U.S. Supreme Court decided that the government engaged in an illegal search when police officers tracked a suspected drug dealer’s movements by attaching a GPS (Global Positioning Satellite) device to the suspect’s car. It was a unanimous decision, so the outcome of the case is less interesting than watching the Justices try to figure out how best to apply 18th century conceptions of privacy in an electronic era.
The reason that Jones was a simple case was that police officers physically attached the GPS device to Jones’ car. That physical intrusion onto the suspect’s property would have been familiar to the 18th century drafters of the 4th Amendment. But what if police officers had tracked Jones’ car through a factory-installed GPS system? What if police officers had tracked Jones’ movements by monitoring the signals from his mobile smartphone?
At present, the Court has little more to go on to decide such issues than the “reasonable expectation of privacy” test it adopted in the case of Katz v. United States, decided in 1967. But what is a reasonable expectation of privacy in an era when computer users give up privacy every time they open a website? (Don’t worry– if you’re reading this, I don’t know who you are.) The Court will inevitably have to struggle with questions like this one in future 4th Amendment cases.