We already know what is possible with the location data stored on our phones, thanks to some cutting-edge academic research.
On Tuesday prosecutors for the Obama administration argued that records of location data gathered by cell-phone companies should be available to law enforcement even when no search warrant has previously been issued by a judge.
In other words, If Uncle Sam wins on this argument, every law-enforcement agency in the country will be able to track your every move. More importantly, access to location data as comprehensive as that available to cell-phone carriers could allow law enforcement to determine everything from your complete social network and your your health status to how likely it is that you'll repay a loan.
The case at hand does not suggest that the Obama administration is attempting to gain this level of insight into the lives of every American citizen, but it's telling that the prosecutors seem ignorant of the power of the data they're requesting.
To understand how important location data is, especially of the variety gathered by smartphones, it's important to understand what academics have already accomplished with this data.
Sandy Pentland, a computer scientist at MIT who coined the term "reality mining" to describe the process of extracting and processing this data, put it this way in a recent essay for Edge.org:
The people who have the most valuable data are the banks, the telephone companies, the medical companies... Who you actually are is determined by where you spend time, and which things you buy... by analyzing this sort of data, scientists can tell an enormous amount about you.
In research published in 2009, Pentland and his colleagues were able to determine, for example, which students were friends based solely on mobile phone location records. Law enforcement could some day use such data to map entire criminal networks, but it could just as easily be used to visualize and contain networks of lawful protestors.
Knowing a person's location reveals their social network, which in turn reveals enormous amounts about who they are and how they are likely to behave. Pentland continued:
[People with access to this data] can do this because the sort of person you are is largely determined by your social context, so if I can see some of your behaviors, I can infer the rest, just by comparing you to the people in your crowd. You can tell all sorts of things about a person, even though it's not explicitly in the data, because people are so enmeshed in the surrounding social fabric that it determines the sorts of things that they think are normal, and what behaviors they will learn from each other.
State and Federal authorities already aggressively employ phone location tracking in the prosecution of crimes, with Federal courts issuing an estimated 20,000 to 30,000 tracking orders a year. A request from congressman Ed Markey (D-MA) revealed that law enforcement requested information from wireless companies more than 1.3 million times in 2011. The National Security Agency has indicated that it may already have the capacity to track ordinary Americans via their phones .
The Supreme Court has ruled that law enforcement needs a warrant to attach a GPS location-tracking device to a car, but in the case at hand, prosecutors are arguing that cell phone location data isn't owned by the user in the first place, and so should be readily available to law enforcement, like bank records. Meanwhile, Supreme Court Justice Scalia believes law enforcement should be able to track you any way it pleases .
All cell phones, and especially smart phones with multiple radios including WiFi, GPS and Bluetooth are able to record especially precise location data, much of which is funneled to device makers as well as cell-phone carriers, especially Google and Apple. What happens to that data varies greatly depending on local laws and the policies of individual providers, and in general cell phone carriers tend to archive the most comprehensive data for the longest period of time. China's government has made plain its plans to track cell phone users via their devices, ostensibly for the improvement of traffic management .
If the Obama administration wins the argument that cell-phone location data should be accessible without a warrant, there is no limit to how useful the resulting flood of "Big Data" could be to law enforcement. And for anyone concerned about privacy or creative intrusions of government into everyday life, that's precisely the problem.
This post will also appear on Quartz, an Atlantic partner site.