The Record, a New Jersey newspaper, has posted an article about the growing ability of law enforcement to trace locations with cell phones.
The article describes some successes for law enforcement. The article also notes that the FBI formed a "a dedicated unit, the Cellular Analysis and Survey Team, in late 2009." According the article, the "unit provides technical assistance, case support and training to federal, state and local law enforcement officers around the nation."
An EFF attorney raises the usual privacy concerns:
Kevin Bankston, a senior staff attorney with the Electronic Frontier Foundation, said the government's reliance on warrantless cell tracking is cause for alarm. "People should be concerned because, whether they realize it or not, they're carrying a tracking device in their pocket," Bankston said. "And phone companies are collecting data about where your phone is located, even when you're not using it, that can reveal a really intimate portrait of how you spend your days and nights, where you go, who you associate with."
"This is a new cache of highly sensitive information. And we think that being able to go into the past and see everywhere you've been based on your cellphone's location is just as invasive as, say, wiretapping your phone calls, which clearly is protected against by the Fourth Amendment."
I agree that the privacy concerns are real – but the Fourth amendment analysis needs to be more precise than simply a concern about where a person is at a particular time. As I have noted elsewhere on the blog, there is a difference between an investigation of a discrete incident or crime, and the general tracking of a person. This is because people generally don't have an expectation of privacy in their location if they could be viewed by the public. However, when the aggregation of tracking data holds the possibility of revealing intimate details of a person's life, then there is a reasonable expectation of privacy and the Fourth Amendment is implicated.