Today, the New Yorker has an article, What Your Cell Phone Can't Tell the Police, that calls into question the accuracy of cell-tower location information (this is different from the insidious GPS tracking data that live in your iPhone). Apart from reliability is the question of whether a warrant is needed to get those records. Riley probably answers that. One more point: this sort of data may be subject to a Daubert challenge.
And the Eleventh Circuit just held (not this week, but June 11), in a case of first impression, that cellphone site location information -- imprecise as it may be -- obtained under the Stored Communications Act (which does not require a warrant) actually does require a warrant.
[W]hether [the Fourth Amendment] protection covers not only content, but also the transmission itself when it reveals information about the personal source of the transmission, specifically his location.The answer,
[W]e hold that cell site location information is within the subscriber’s reasonable expectation of privacy. The obtaining of that data without a warrant is a Fourth Amendment violation.Of course, then the defendant got Leon-ed. But this is an important case for many reasons, not the least of which is that the Court found that the Fourth Amendment demanded more than the statute required.
Maybe the law is starting to catch up with technology. Slowly. At least the courts recognize that data is different. Quite a week for cell phones.