Should police need probable cause to request mobile-phone location data?

Please note that this post is from 2010. Evaluate with care and in light of later events.

There are currently no firm standards on the kinds of Fourth Amendment protections that should apply to mobile-phone tracking data. This is becoming an issue as GPS and other tracking technologies have been added to cell phones to satisfy E911 requirements (to find callers in emergencies), and as police agencies have discovered the potential benefits of cell-phone location data:

On Friday, the first federal appeals court to consider the topic will hear oral arguments (PDF) in a case that could establish new standards for locating wireless devices. In that case, the Obama administration has argued that warrantless tracking is permitted because Americans enjoy no “reasonable expectation of privacy” in their–or at least their cell phones’–whereabouts. U.S. Department of Justice lawyers say that “a customer’s Fourth Amendment rights are not violated when the phone company reveals to the government its own records” that show where a mobile device placed and received calls.

via Feds push for tracking cell phones | Politics and Law – CNET News.

Magistrate Judge Lisa Lenihan wrote the lower-court opinion [PDF], which was signed on to by four other magistrate judges. The lower court emphasized the importance of requiring a probable-cause standard for accessing location data — the same standard used for search warrants generally — and not a “articulable, reasonable belief” standard used to obtain so-called “pen-register” data (information that includes the phone number called, when, and for how long).

Pen-register data is subject to a lower standard because the courts consider that individuals knowingly provide the data to a third party (the telephone company) and thus have a limited expectation of privacy for that information (vs. their actual telephone conversations, for example, which have a higher level of protection due to a higher expectation of privacy).

The lower-court wrote, essentially, that location date can potentially reveal “extraordinarily personal and sensitive” information about a person without the involvement of that person (or their attorney) in the proceedings (it is “ex parte,” in the language of the court). Balancing the interests, says the court, means that a probable-cause standard is most appropriate. This balancing, along with detailed statutory interpretation, forms the core of the court’s analysis.

One weakness I see is that the court does not do a deep analysis of a “reasonable expectation of privacy” and the issue that giving that information to third parties reduces the expectation of privacy, noting only the the E911 legislation suggests that individuals have, and should have, a strong privacy expectation in their location data.

I think this is a good, balanced decision, but I wish it had dealt more with the potential attack on it due to the third-party data issue. I’ll be interested to see what happens at the 3rd Circuit (I expect it to be overturned, unfortunately).

Update as of July 30, 2013 from the Fifth Circuit on a similar case: Warrantless Cellphone Tracking Is Upheld.