Modern tools like GPS and cell-phone tracking make police surveillance dramatically easier and cheaper than ever before, two privacy experts say this month in the Yale Law Journal. In 2012, for instance, the FBI had about 3,000 GPS tracking devices deployed on suspects' cars across the U.S., they say--a level of vehicle surveillance they estimate wouldn't have been possible even with every FBI agent in the field tailing cars for 24 hours every day.
When new techniques make monitoring the public literally orders of magnitude cheaper, they argue, courts ought to see that as a sign that the new methods are violating traditional expectations of privacy and keep a close watch on how officers are using those tools.
The U.S. Supreme Court ruled in United States v. Jones in 2012 that police monitoring a GPS unit and transmitter they attached to a suspect's car without a proper warrant violated his Fourth Amendment rights. But the justices were divided on how to determine when a new law enforcement tool requires a warrant or other court scrutiny, argues the paper by Kevin Bankston, the policy director of the New America Foundation's Open Technology Institute, and independent privacy researcher Ashkan Soltani.
"Trying to make sense of the Jones concurrences and reduce them to a clear and administrable rule--or, alternatively, arguing that they make no sense and cannot be so reduced--has become something of a cottage industry amongst privacy law scholars," the authors wrote.
They argue that people's expectations of privacy are driven by a mix of legal restrictions and practical restrictions--like the fact that the FBI can't deploy all of its agents to follow suspects without sleep for days at a time. So, they say, when new technology makes surveillance cheaper by an order of magnitude--that is, when the dollar cost falls by a factor of 10--courts should recognize that an existing expectation of privacy is likely being breached.
"Drawing the line at an order of magnitude is admittedly somewhat arbitrary, " they write, "but is also an indisputable benchmark and easily applicable test for whether or not a particular type of surveillance has become radically less expensive, which is ultimately the question on which we are suggesting courts focus."
Automated GPS logging with a hidden transmitter that sends a car's location to a central server costs about 36 cents per hour, while actually following a suspect's car costs hundreds of dollars in agent salaries per hour, the authors estimate, so the threshold would be met.
On the other hand, switching from a standard five-agent surveillance team to using a more primitive short-range transmitter that lets one pair of agents trail the car from up to a couple miles away only cuts costs by about 60%, so it wouldn't be treated as a fundamental change.
"Using order-of-magnitude difference as a rule of thumb is just one way of using cost as a metric, and we welcome other such proposals for assessing whether a radical technology-prompted rights-shift has occurred," the authors wrote.