If you are a criminal defense lawyer and you haven't encounterd the use of cell phone records to establish someone's locations you probably will soon. The accuracy of those records will be left to the subject of another post. For now, it is enough to say that no competent lawyer should accept the goverment's interpretation of the cell phone data.
The fact is that most of are being tracked 24 hours a day and don't even know it. Your cell phone is constantly communicating with a cell tower, and that informaiton is recorded. What happens though if the evidence is no longer available? Based on the recent revelations about the secret NSA surveillance program a Florida defendant is not willing to take no for offense. Terrance Brown has filed a motion asking the Court to order the NSA to turn over his records. The motion is still under consideration - although few people probably give him much chance of success.
There should be no reason why such records should not be discoverable in some cases though. The government has an obligation to turn over exculpatory information (Brady evidence). That obligation exists even if they don't know about it. They still must seek it out - the question will be whether they have an obligation to seek out classified information - and whether they even have that authority.
I'm sure we haven't seen the last of this issue.