In the case of the United States versus Quartavious Davis, Mr. Davis was convicted of several armed robberies that occurred at different times and in several different locations. In order to prove that Davis was in the general vicinity of the robberies when they occurred, the prosecutor presented "cell site location information" at Davis' trial. That information consisted of a record of the calls supposedly made by Davis as well as calls that he received. It also consisted of information about which cell phone towers carried those calls to and from Davis. Typically when you make a call using your cell phone, the cell tower that is closest to you will carry that call to whomever you are calling. By knowing which cell towers were used to send Davis' calls, the prosecutor was able to show approximately where Davis' phone was located on certain dates and at certain times. Coincidentally, the prosecutor argued, Davis' phone was located in the same general vicinity as the robberies that occurred and at the same time that they occurred. Therefore, the prosecutor argued, Davis was one of the robbers.
Davis objected to the cell cite location information being presented to the jury because the government agents who obtained that information did so without first getting a search warrant. They instead obtained the information by getting a court order.
The court of appeals deciding Davis' case agreed that the Fourth Amendment to the United States Constitution required that the agents get a warrant before they could obtain the cell cite location information. Davis, the appellate court said, had a "reasonable expectation of privacy" in that information. The agents mere reliance upon a court order was not good enough.