Small cells, big problems: the increasing precision of cell site location information and the need for Fourth Amendment protections.

• Author: Bloom, Robert M.

TABLE OF CONTENTS INTRODUCTION I. A LOCATION TRACKER ON EVERY LAMPPOST: CSLI, SMALL CELLS, AND THE FOURTH AMENDMENT A. CSLI and the Rise of Small Cell Technologies 1. Cell Phones and Traditional Cellular Networks 2. Small Cell Technology and the Growing Precision of CSLI B. The Fourth Amendment and Location Tracking C. The Archaic Protections of the Stored Communications Act II. AN INDIVIDUAL'S PERSONAL HISTORY OR A SERVICE PROVIDER'S BUSINESS RECORD?: COURTS SPLIT OVER FOURTH AMENDMENT'S APPLICATION TO CSLI A. Courts that Have Held that the Fourth Amendment Requires the Government to Obtain a Warrant Before Reviewing CSLI B. Courts That Have held that the Fourth Amendment Does Not Require Warrants to Review CSLI III. A RIGHT TO BE FREE FROM DRAGNET SURVEILLANCE: THE FOURTH AMENDMENT PROTECTS A PERSON'S CSLI A. People Possess a Reasonable Expectation of Privacy in Their Location History B. The Third-Party Doctrine Does Not Preclude Protection C. Bringing the SCA into the 21st Century CONCLUSION INTRODUCTION

Dissenting from the U.S. Supreme Court's 1989 decision in Florida v. Riley, (5) Justice Brennan bemoaned the Court's choice to allow the government to observe a person's home via helicopter without a warrant. (6) Justice Brennan found it cause for concern that a four justice plurality of the Court was willing to "remove virtually all constitutional barriers to police surveillance" using this advanced technology. (7) To close his dissent, Justice Brennan invoked one of the most powerful stories of police surveillance in western culture: George Orwell's 1984. (8) Noting the eerie parallel between the police surveillance methods at issue before the Court in Riley and Orwell's vision of government helicopters darting across the sky, Justice Brennan quoted the description of the infamous figure that loomed over Orwell's dystopian world: "The black-mustachio'd face gazed down from every commanding corner.... BIG BROTHER IS WATCHING YOU, the caption said...." (9)

From a rudimentary tape recording device (10) to a sophisticated cell phone-computer, (11) the U.S. Supreme Court has struggled to balance the Fourth Amendment's protections against the steady technological advancements in police surveillance. The Court has confronted a wide range of surveillance technologies, from helicopters and heat rays to beepers and GPS trackers. (12) Today, however, the greatest threat to privacy is not the latest sophisticated government technology. It is a small rectangular box that resides in the pocket of nearly all Americans.

As the Court observed, cell phones, given their huge storage capacity, contain the sum of an individual's private life including photos, bank statements, videos, contacts, a literal trove of personal data, which the Court has sought to protect by requiring police to obtain a warrant before searching a cell phone. (13) But besides the intimate details contained therein, cell phones also invisibly chart the path of a person's movements throughout his or her day by generating what it is known as cell site location information (CSLI). (14)

Courts and scholars are split over whether police should obtain a warrant before reviewing CSLI. (15) Some view CSLI as blips of data generated and owned by private companies in the course of their business operations. (16) Under this view, police can review CSLI just as they could any other business record under the third-party doctrine exception. (17) Others view CSLI, when taken all together, as a rich tapestry that reveals deeply personal details of an individual's life. (18) Under this view, police can only review CSLI after obtaining a warrant because people have a fundamental privacy right against having their every movement tracked by the government despite technological evolutions.

Because of recent evolutions in cellular network technology, CSLI will soon paint an even more precise picture of a person's location history. (19) Cellular service providers, which have traditionally relied on large cell phone towers to send out signals, have started to add miniature cell phone towers known as "small cells" to their networks. (20) Small cells allow service providers to dramatically increase the number of cell towers in a particular area. (21) Although this provides many benefits to cell phone users, the increased concentration of cell towers means that CSLI will reveal a user's location down to a matter of feet instead of a matter of miles. (22)

This Article argues that the rise of small cells in cellular networks will make CSLI so accurate that it must fall under the Fourth Amendment's protection. (23) Part I discusses how cell phones operate relative to the collection of CSLI, the Fourth Amendment doctrines relevant to the collection of CSLI, and the current statutory framework by which the government obtains CSLI. (24) Part II reviews the current split amongst courts regarding whether the Fourth Amendment is applicable to CSLI. (25) Part III argues that the Fourth Amendment requires the government to obtain a particularized warrant supported by probable cause before reviewing CSLI. (26) Part III explains that the third-party doctrine, which has traditionally been regarded as an exception to the Fourth Amendment, does not apply to CSLI because people have a reasonable expectation of privacy in the detailed location history cell phones generate, unlike the information traditionally covered under the doctrine. (27)

1. A LOCATION TRACKER ON EVERY LAMPPOST: CSLI, SMALL CELLS, AND THE FOURTH AMENDMENT

   This Part provides an introduction to CSLI and the Fourth Amendment. (28) Section A explains how cell phones work and how cell phone service providers increasingly employ small cell technologies to operate their networks. (29) Section B provides an overview of the Fourth Amendment principles relevant to CSLI, including the U.S. Supreme Court's case law on location-based technologies and the third-party doctrine. (30) Section C provides an overview of the statutory limitations on the government's power to obtain CSLI. (31)

   1. CSLI AND THE RISE OF SMALL CELL TECHNOLOGIES

1. Cell Phones and Traditional Cellular Networks

   In December 1947, while working as an engineer in Bell Labs, Douglas H. Ring wrote an internal memorandum with the subject: "Mobile Telephony--Wide Area Coverage." (32) In his memorandum, Ring envisioned "[a] highly developed mobile telephone system" that would "ultimately be capable of providing service to a mobile unit from any part of the country at any place in the country." (33) His system would operate by precisely arranging radio transmitters in a hexagon honey-comb pattern, with three transmitters placed at the corners of each hexagon. (34) This would allow for the repeated use of certain frequencies with limited interference. (35)

   Although it would take years for technology to catch up with his vision, Ring's proposal provided a significant foundation for our modern cellular networks. (36)

   Modern cellular networks use base stations, also known as cell towers or cell sites, arranged in Ring's hexagon pattern to provide radio coverage to the largest amount of space in the most efficient manner. (37) Base stations are usually equipped with three antennas that each cover 120 degrees of area, thereby ensuring that each base station sends out signal in a complete circle. (38)

   A cell phone connects to a base station whenever it places or receives a call or text message. (39) When a cell phone connects to the base station, it provides the user's telephone number as well as other information, including the device's International Mobile Equipment Identifier, (40) a unique number that identifies the particular cell phone (like a VIN number for cars). The wireless service provider, which maintains the cellular network, records which cell phone connected to the network, when it connected, and through which base station it connected in order to bill the account associated with that device. (41) This information is known generally as CSLI. (42)

   The rapid rise of smartphones and other mobile computing devices has threatened to overload the traditional cellular network. (43) In 2012, Americans used 1.468 trillion megabytes of data annually. (44) In 2014, that number more than doubled, as Americans used 4.06 trillion megabytes of data annually. (45) Moreover, each year more and more people are turning away from laptop and desktop computers to rely almost exclusively on their mobile devices. (46) Some predict that by 2017, mobile devices will be the primary generators of all Internet traffic, (47) thus the need for more CSLI locations and technology which is discussed in the next Section. In order to address these growing capacity challenges, many service providers are turning to small cell technologies. (48)

   2. Small Cell Technology and the Growing Precision of CSLI

   Small cells are miniature base stations that provide a small range of cellular signal in areas that are either overburdened or underserved by traditional cellular networks. (49) Small cells typically have a range of nine meters (about thirty feet) to several hundred meters as compared to traditional cell towers, which cover several "tens of kilometers." (50) Small cells can serve urban communities, where the high population density puts a massive strain on the network, or rural communities where installing a large base station would not be cost-effective. (51) Small cells have many different names based on their different functions and uses, including femtocells, picocells, microcells, and metrocells. (52)

   Femtocells are compact base stations, some about the size of a broadband router, developed for residential use. (53) For those who have poor cell phone coverage at home, femtocells put a cell phone tower into the home itself." (54) Several major wireless networks, including Verizon and AT&T, sell femtocells directly to consumers for use in their homes for approximately two hundred fifty...