Case5:15-xr-90304-HRL Document30 Filed07/29/15 Page4 of 46 1 2 Blaze Testimony at 54. Densely populated urban areas therefore have more cell towers covering 3 smaller geographic locations. For example, the Public Defender informs the Court that within 4 three miles of the San Jose Federal Courthouse, there are 199 towers (with applications for three 5 more currently pending) and 652 separate antennas. Opp. at 3. Within just one mile of the 6 Federal Courthouse in New York City, there are 118 towers and 1,086 antennas. Id. 7 United States District Court Northern District of California spectrum bandwidth, usually requiring, again, that the area covered by each sector be made smaller and smaller. In addition to the large, three-sided cell towers, smaller and smaller base stations are 8 becoming increasingly common. Examples include microcells, picocells, and femtocells, all of 9 which cover a very specific area, such as one floor of a building, the waiting room of an office, or 10 a single home. Blaze Testimony at 43-44. This proliferation of base stations to cover smaller 11 areas means that “knowing the identity of the base station (or sector ID) that handled a call is 12 tantamount to knowing a phone’s location to within a relatively small geographic area . . . 13 sometimes effectively identifying individual floors and rooms within buildings.” Id. at 55-56. 14 Although the ability of cellular service providers to track a cell phone’s location within an area 15 covered by a particular cell site might vary, it has become ever more possible for the government 16 to use CSLI to calculate a cell phone user’s “locations with a precision that approaches that of 17 GPS.” Id. at 53. 18 The government acknowledged as much at oral argument, conceding that CSLI has gotten 19 more precise over the years. Hr’g Tr. at 32:5-9. The fact is new tools and techniques are 20 continually being developed to track CSLI with greater precision. Cellular service providers, for 21 instance, can triangulate the location of a cell phone within an area served by a particular cell site 22 based on the strength, angle, and timing of that cell phone’s signal measured across multiple cell 23 site locations. Blaze Testimony at 56. 24 Lastly, the volume of location data generated by an individuals’ cell phone can be 25 immense, as the ACLU points out. See ACLU Br. at 5-7; ECF No. 19-1, Declaration of Nathan 26 Freed Wessler (“Wessler Decl.”). For example, in United States v. Carpenter, a case now pending 27 28 4 Case No. 15-XR-90304-HRL-1(LHK) ORDER AFFIRMING DENIAL OF APPLICATION FOR HISTORICAL CELL SITE LOCATION INFORMATION