In order to convince AT&T, Verizon, or whoever to cough up someone's mobile phone tracks, cops need to present something approved by a judge. Basic account information like name, address, and credit card can be obtained with a subpoena. Anything beyond that, and the judge approved thing comes in two standard forms: a court order or a warrant. To get an order, law enforcement needs to prove that a certain record is relevant and material to an ongoing investigation. Getting a warrant, on the other hand, requires probable cause. The latter needs more proof that the data is worth getting (read: harder for the cops) than the former. Simple, right?
But here's where it gets tricky, says the Santa Clara Law Review: "As one court has appropriately observed, "the recently minted standard of electronic communication via emails, text messages, and other means opens a new frontier in Fourth Amendment [the right against unreasonable searches and seizures] jurisprudence that has been little explored." You see what that is? It's a shoulder shrug-a we have no idea where all this new stuff stands. So on a state level, the courts don't always agree what a judge should approve for a certain piece of information. Real time location tracking of a cell phone by law enforcement, for instance, has courts split. "Some say that the government needs a warrant and probable cause to track this kind of information," explains Catherine Crump, an attorney at the ACLU, "others have held that they need to meet the lower relevant and material standard."
More at link..
"Which brings us around to the detailed location history that the iPhone keeps of its user. Because that data is stored on the phone and on the computers that the phone is synched to, cops would have to physically search your phone and computer. That type of thing requires probable cause, which is tough. Law enforcement would be better off just getting a court order for historical location records. The records kept by your cell service provider seem to raise much bigger issues about privacy."
http://gizmodo.com/5795861/how-the-police-get-your-phone-records
I dunno - maybe they had to subpoena the records and go through a bunch of legal stuff? Clearly, an attorney, I am not!