Location Tracking: Muddled and Uncertain Standards Harm Americans’ Privacy

Over the past decade, cell phones have gone from a luxury good to an essential communications device. As of December 2009, more than 90 percent of the overall population of the United States subscribed to cell phone service—an estimated 285.6 million people. While cell phones are best known as devices used to make voice calls and send text messages, they are also capable of being used as tracking devices. As a result, cell phone technology has given law enforcement an unprecedented new surveillance tool. With assistance from mobile phone carriers, the U.S. government now has the technical capability to track any one of the nation’s hundreds of millions of cell phone owners, for 24 hours a day, for as long as it likes. Whether it is a visit to a therapist or liquor store, church or gun range, many individuals’ locations will be available either in real time or months later.

Because of the sensitivity and invasiveness of location records, many advocates, including the American Civil Liberties Union, argue that law enforcement agents should always be required to obtain a warrant and show probable cause to gain access to them, no matter the technology employed or the age of the records. Unfortunately, it is unclear how frequently law enforcement agents obtain a warrant and show probable cause and how frequently courts rule that this is the legal minimum. While the Department of Justice has issued recommendations stating that prosecutors should obtain a warrant and show probable cause in some circumstances, documents obtained through Freedom of Information Act requests by the American Civil Liberties Union and the Electronic Frontier Foundation (EFF) demonstrate that some U.S. Attorney’s Offices do not consistently follow these recommendations.

Moreover, it is often difficult to tell what the rule of law is in a given judicial district. Because government applications to track cell phones are nearly always filed under seal, and court orders to grant or deny them are also nearly always under filed seal, the rule of law is often not public. Those limited decisions that are public reveal that courts have split on the circumstances under which the government must obtain a warrant and show probable cause to obtain this information. Unfortunately, federal prosecutors have effectively prevented the creation of a uniform standard by nearly always refusing to seek appellate court decisions on the issue.

Congress should clarify the law by updating the electronic surveillance statutes. Congress has not meaningfully revised the electronic surveillance laws since 1986. Courts and advocates alike struggle to figure out how to apply this outdated scheme to technology that was not contemplated when the law was written. Congress should update these laws and should do so by requiring the government to obtain a warrant based on probable cause. The sum of the information gathered from the sweeping surveillance of a person’s movement can “reveal[ ] an intimate picture of the subject’s life that he expects no one to have—short perhaps of his spouse.” ¹United States v. Maynard, No. 08-3030, 2010 WL 3063788, at *14, 79 U.S.L.W. 1254(D.C. Cir. Aug. 6, 2010) (holding that continuous GPS surveillance of an individual’s movements without a warrant violates his reasonable expectation of privacy). The warrant and probable cause requirement is designed to ensure that civil liberties are safeguarded when the government seeks to access such sensitive information.

Background

Cell phones yield several types of information about their users’ past and present location and movements that are of interest to the government: cell site location data, triangulation data, and Global Positioning System data.

The most basic type of cell phone location information is “cell site” data, or “cell site location information,” which refers to the identity of the cell tower from which the phone is receiving the strongest signal and the sector of the tower facing the phone. This data is generated because, whenever users have their cell phones on, the phones automatically scan for the cell tower and the sector of that tower that provides the best reception; approximately every seven seconds, the phones register their location information with the network. ²In re Application of United States for Order Directing Provider of Electronic Communication Service to Disclose Records to Government, 534 F. Supp. 2d 585, 589-90 (W.D. Pa. 2008) (Lenihan, M.J.), rev’d on other grounds, No. 08-4227, 79 U.S.L.W. 1324 (3d Cir. Sept. 7, 2010). The carriers keep track of the registration information to identify the cell tower through which calls can be made and received. The towers also monitor the strength of the telephone’s signal during the progress of the call to manage the hand-off of calls from one adjacent tower to another if the caller is moving during the call.

Government requests for cell site location data are usually of two types: historical cell site data, which can be used to retrace previous movements, or prospective cell site data, which can be used to track the phone in real time. Prospective data may encompass cell site information whenever the phone is on.

The precision of cell site location information depends, in part, on the size of the coverage area of each cell tower. This means that as the numbers of cell towers have increased and the coverage area for each cell tower has shrunk in response to demand for wireless technology, cell site location information has become more precise.

A government expert stated in 2006 that cell site location information can be as accurate as 200 meters in some areas. ³Declaration of Henry Hodor at 9, available at http://www.aclu.org/pdfs/freespeech/cellfoia_release_4805_001_20091022.pdf. But the latest generation of cellular towers now may cover an area as small as a tunnel, a subway, a specific roadway, a particular floor of a building, or even an individual home or office. Further improvement in precision can be expected given the explosive demand for wireless technology and its new services, to the point that “[t]he gap between the locational precision in today’s cellular call detail records and that of a GPS tracker is closing, especially as carriers incorporate the latest technologies into their networks.” ⁴Hearing on Electronic Communications Privacy Act Reform and the Revolution in Location Based Technologies and Services before the H. Comm. on Judiciary’s Subcomm. on the Constitution, Civil Rights, and Civil Liberties, 111th Cong. (2010), statement of Professor Matt Blaze at 13-14, available at http://judiciary.house.gov/hearings/pdf/Blaze100624.pdf.

The government can currently obtain location data at a high level of accuracy through “triangulation,” which entails collecting and analyzing data of the precise time and angle at which the cell phone’s signal arrives at multiple cell towers. Current technology can pinpoint the location of the cell phone to an accuracy of within 50 meters or less anytime the phone is on, and the accuracy will improve with newer technology. ⁵Id. at 10.

The availability of the information and the length of time this information is stored depend on the policies of the cell phone carrier, but some carriers already appear to be recording and storing “frequently updated, highly precise, location information not just when calls are made or received, but about every device as it moves about the networks.” ⁶Id. at 11. It is likely that, as technology progresses, more carriers will store more detailed records of individuals’ locations for a longer period of time.

A cell phone that has special GPS satellite receiver hardware built into it can determine its precise location by receiving signals from global positioning satellites. An increasing number of phones, particularly smartphones, contain such GPS chips.

How often the cell phone reports location information to the network using the GPS depends on the application software that the phone is running. Current GPS technology is able to pinpoint location with accuracy when it is outdoors, typically achieving accuracy of within 10 meters. With “assisted GPS” technology, which combines GPS and triangulation, it is possible to obtain such accurate location information even when the cell phone is inside a home or a building.

Current Legal Practices
For Accessing Location Information

Unfortunately, it is currently unclear under what circumstances federal prosecutors obtain a warrant and show probable cause to access cell phone location information and under what circumstances courts have held that this is the legal minimum showing and process required under the law. Although DOJ has issued guidelines for prosecutors that require probable cause in some circumstances, these are not consistently followed. Because the vast majority of judicial decisions on point are sealed, and those limited number that are public are in conflict, the state of the law is unclear. Federal prosecutors essentially never appeal adverse rulings to circuit courts. Clarity is unlikely anytime soon unless Congress acts.

Department of Justice Standards.

DOJ asserts it should have access to most kinds of location information without having to obtain a warrant and show probable cause. Instead, DOJ argues that the government should be able to obtain most cell phone location information by demonstrating to a judge or magistrate only that the information is relevant and material to an ongoing criminal investigation. According to a document obtained by the ACLU and the EFF through a FOIA request, it is DOJ’s policy to obtain mobile location information under the following standards ⁷Mark Eckenwiler, Current Legal Issues In Phone Location, slide 20, available at http://www.aclu.org/pdfs/freespeech/18cellfoia_release_CRM-200800622F_06012009.pdf.:

DOJ maintains that the government need not obtain a warrant and show probable cause to track people’s location with only one exception: real-time GPS and triangulation data. Since at least 2007, DOJ has recommended that U.S. attorneys around the country obtain a warrant based on probable cause prior to engaging in these forms of cell phone tracking. ⁸E-mail from Brian Klebba, GPS or “E-911-data” Warrants, Nov. 17, 2009, available at http://www.aclu.org/pdfs/freespeech/cellfoia_dojrecommendation.pdf.

However, not all U.S. Attorney’s Offices obtain a warrant and show probable cause even in the limited circumstances in which DOJ recommends that they do so. ⁹Letter from William G. Stewart II, to Catherine Crump, Mobile Phone Tracking (Items 3-5)/DNJ, Dec. 31, 2008, available at http://www.aclu.org/pdfs/freespeech/cellfoia_released_074132_12312008.pdf; letter from William G. Stewart II to Catherine Crump, Mobile Phone Tracking(Items 3-5)FLS, Dec. 31, 2008, available at http://www.aclu.org/pdfs/freespeech/cellfoia_released_074135_12312008.pdf. The ACLU’s and EFF’s FOIA litigation revealed that U.S. Attorney’s Offices in the District of New Jersey and the Southern District of Florida have obtained even the most precise cell tracking information without obtaining a warrant and showing probable cause. ¹⁰Id. Because the FOIA litigation focused on only a small number of U.S. Attorney’s Offices around the country, it may well be that many other offices also do not follow DOJ’s recommendation.

In fact, this practice may be widespread. There are no published legal opinions on the lawfulness of warrantless cell phone tracking in either the District of New Jersey or the Southern District of Florida, and yet the FOIA litigation proved conclusively that cell phone tracking occurs in those districts and indeed that federal prosecutors do not feel obligated to show probable cause even where DOJ recommends it. In the vast majority of judicial districts in this country, there are no decisions addressing cell phone tracking, yet such tracking was occurring in every district subject to the FOIA even where there was no published opinion setting out the circumstances in which the practice is permissible. ¹¹See http://www.aclu.org/free-speech/aclu-lawsuit-uncover-records-cell-phone-tracking. Given that cell phone tracking is now a decades-old law enforcement technique that has proven useful, we must assume authorities use it in all or essentially all parts of the country, most frequently under an unknown standard.

Procedures for Gathering Location Information.

The reason so little information is available arises in part from the unique procedural posture in which cell phone tracking applications reach courts. For legitimate reasons, applications to track cell phones are often filed under seal. Law enforcement agents sometimes need to prevent the targets of government surveillance from learning that they are investigative subjects.

However, the orders granting or denying surveillance applications are also often filed under seal. Moreover, the orders are routinely ordered sealed “until further order of the Court.” ¹²In re Sealing and Non-Disclosure of Pen/Trap/2703(d) Orders, 562 F. Supp. 2d 876, 878 (S.D. Tex. 2008) (Smith, J.). Because there is no end date on sealing, and no one other than the government and the court knows the contents of the order, in most cases there is no one with both the motivation and the knowledge to move to unseal them. Public access to the courts would be better served were judges to require that redacted copies of both the applications and the orders be filed publicly. This would allow the public to know the legal standards applied by the courts.

This is an unfortunate break with the usual working of the judiciary, where a commitment to transparency is not only embodied in the common law right of access but also constitutionally required by the First Amendment. ¹³Press-Enterprise Co. v. Superior Court of California, 478 U.S. 1, 8 (1986). Some magistrate judges such as Judge Stephen Wm. Smith, who has testified before Congress on the issue, are notable exceptions to this trend. Smith has issued an opinion putting an end to indefinite sealing of the surveillance orders he is called upon to issue. ¹⁴In re Sealing and Non-Disclosure of Pen/Trap/2703(d) Orders, 562 F. Supp. 2d at 891 (holding that “documents authored or generated by the court itself” are entitled to heightened public access rights).

Ex parte adjudication of cell phone tracking applications also contributes to the dearth of published legal opinions on the subject. Ex parte proceedings—when the government presents its arguments in favor of surveillance without presentation of any opposing argument—will favor unpublished decisions because there is no motivation for the only party present, the government, to ask the court to issue a public decision. The ACLU and others have tried to remedy the situation by offering to submit amicus briefs to present the pro-privacy viewpoint. Unfortunately, because many applications for surveillance are so time-sensitive that they must be acted on immediately, some judges have taken the position that there is unlikely to be a practical way to permit amicus participation. ¹⁵See, e.g., Letter from Hon. David Martin and Hon. Lincoln Almond, U.S. magistrate judges, to Catherine Crump, Cell phone tracking, March 12, 2010 (on file with author).

Reaction From the Judiciary.

From the limited published opinions available, it is apparent that courts do not always find in favor of the government position that it need not obtain a warrant and show probable cause for some forms of cell phone tracking. In fact, the government frequently loses. The “strong majority” of district and magistrate judges have concluded in recently published opinions that the government lacks statutory authority to obtain real-time cell site location without a showing of probable cause. ¹⁶In re Applications of United States for Orders Pursuant to 18 U.S.C. §2703(d), 509 F. Supp. 2d 76, 78 (D. Mass. 2007) (Stearns, D.J.). Because the government has never followed through on an appeal of an adverse decision addressing real-time tracking, no circuit court has had the opportunity to review these holdings.

The government did appeal an adverse decision addressing historical information. In a decision joined by all the magistrate judges in the Western District of Pennsylvania, a magistrate judge there held that government requests for court orders requiring mobile carriers to disclose their customers’ location information must be based upon probable cause. ¹⁷In re Application of United States for Order Directing Provider of Electronic Communication Service to Disclose Records to Government, 534 F. Supp. 2d at 585-86. After the decision was summarily affirmed by the district court, the government appealed to the Third Circuit. In a decision issued Sept. 7, the circuit concluded that judges have “the option to require a warrant showing probable cause,” although it cautioned that “it is an option to be used sparingly.” ¹⁸In re Application of United States for Order Directing Provider of Electronic Communication Service to Disclose Records to Government, No. 08-4227, ___F.3d ___, 79 U.S.L.W. 1324 (3d Cir. Sept. 7, 2010).

Until the action by the magistrate judges in the Western District of Pennsylvania forced the government’s hand—by making it impossible to get an order in that district under the “relevant and material” standard—a location tracking case had never been appealed to the appellate court in any circuit. By not appealing, federal prosecutors avoid binding precedent that might tie the government’s hands in other cases. ¹⁹In re Application of United States for Order Authorizing (1) Installation and Use of Pen Register and Trap and Trace Device or Process, (2) Access to Customer Records, and (3) Cell Phone Tracking, 441 F. Supp. 2d 816, 827-28 (S.D. Tex. 2006) (Smith, M.J.). Decisions by magistrate judges and district court judges are not binding precedent, even on other judges of the same district court. ²⁰Federal Trade Commission v. Tariff, 584 F.3d 1088, 1092 (D.C. Cir. 2009). So long as there are at least some judges in a district who believe that warrantless cell phone tracking is permissible, the government will be able to get its applications approved at least some of the time.

This is exactly the situation in the Southern District of New York, where one district court judge has approved warrantless real-time cell phone tracking in the absence of probable cause and another has held that probable cause is required. ²¹Compare In re Application of United States for Order for Prospective Cell Site Location Information on Certain Cellular Telephone, 460 F. Supp. 2d 448 (S.D.N.Y. 2006) (Kaplan, J.), with with In re Application of United States for Order Authorizing Use of Pen Register With Caller Identification Device Cell Site Location Authority on Cellular Telephone, 2009 WL 159187 (S.D.N.Y. 2009) (McMahon, J.). Although the government initially filed a notice of appeal with regard to the adverse ruling, after the ACLU received permission to submit an amicus brief in the Second Circuit, the government sought and obtained multiple extension requests and then voluntarily dismissed its appeal. ²²In re Application for Cell Site Order, Case No. 09-0807 (2d Cir. docketed Feb. 27, 2009). Judges in the Eastern District of New York also split on the question, and only prosecutors and the courts know how this issue is handled in most of the country, where there are no published opinions. ²³Compare In re Matter of Application of United States for Order (1) Authorizing Use of Pen Register and Trap and Trace Device and (2) Authorizing Release of Subscriber Information and/or Cell Site Information, 396 F. Supp. 2d 294 (E.D.N.Y. 2005) (Orenstein, M.J.) (probable cause for prospective tracking), and In re Application of United States for Order Authorizing (1) Use of Pen Register and Trap and Trace Device With Prospective Cell-Site Information and (2) Release of Historical Cell-Site and Subscriber Information, 2009 WL 1530195 (E.D.N.Y. 2009) (Pollak, M.J.) (probable cause for prospective tracking, reversed by Judge Nicholas G. Garaufis), with In re Application of United States for Order Authorizing (1) Use of Pen Register and Trap and Trace Device With Prospective Cell-Site Information and (2) Release of Historical Cell-Site and Subscriber Information, 2009 WL 1594003 (E.D.N.Y. 2009) (Garaufis, D.J.) (no probable cause necessary for prospective tracking).

The state of the law regarding cell phone tracking is characterized by secrecy and contradictory rulings. This is precisely the opposite of the uniformity and openness that are cornerstones of the rule of law in the United States.

Congress Should Reform the Electronic Surveillance Laws and Require a Warrant and Probable Cause for All Forms of Cell Phone Tracking

Cell phone tracking is a powerful law enforcement tool that has been in use for at least a decade, and yet the baseline standards for when, as a statutory matter, law enforcement may use this tool without a warrant and probable cause are muddled. The usual method by which courts gradually clarify the law has largely been frustrated by prosecutors’ decisions not to appeal adverse rulings and lack of a suppression remedy for violations of the electronic surveillance statutes.

If there is to be clarity in the law, Congress must act. The relevant federal electronic surveillance statutes are quite old, largely dating to 1986, and it is challenging for courts and advocates on all sides of the issue to figure out how to apply them to circumstances their drafters did not contemplate. In struggling to determine whether magistrate judges have the discretion to require the government to proffer probable cause when it seeks historical cell tracking information, the Third Circuit described itself as “stymied by the failure of Congress to make its intention clear.” ²⁴In re Application of United States for Order Directing Provider of Electronic Communication Service to Disclose Records to Government, 3d Cir., No. 08-4227, slip op. at 28. Cell phone tracking is too important—to the privacy of the nation’s nearly 290 million cell phone subscribers and to the efficacy of law enforcement efforts—for Congress to leave courts struggling to apply an outdated statutory framework to a vital new technology.

Congress should act now because, however prevalent the technique may already be, it is evidently becoming even more widespread. It has recently come to light that:

Sprint Nextel has even set up a dedicated Web site so that law-enforcement agents can access the records from their desks—a fact divulged by the company’s “manager of electronic surveillance” at a private Washington security conference last October. “The tool has just really caught on fire with law enforcement,” said the Sprint executive, according to a tape made by a privacy activist who sneaked into the event. ²⁵Michael Isikoff, The Snitch in Your Pocket, Newsweek, Feb. 19, 2010.

Cell phone tracking is not just a useful tool, but increasingly it is a cheap and convenient tool.

Cell phone tracking is not an issue that impacts only those whom the police suspect of criminal activity. In June, the ACLU and EFF filed an amicus brief in the case of United States v. Soto. ²⁶Brief of Amici Curiae in Support of Motion To Suppress, United States v. Soto, Case No. 09-cr-200 (D. Conn. June 18, 2010), available at http://www.aclu.org/files/assets/2010-6-18-USvSoto-AmiciBrief.pdf. In Soto, the FBI sought and received tracking information without a warrant, not just for the criminal defendant, but for about 180 other people. Although the details remain unclear because the government’s surveillance application is under seal, it appears that the government took the dragnet approach of getting location information for a large number of innocent people to try to figure out who was involved in the crime.

The mass tracking in Soto is not an isolated incident. It is just one manifestation of the “communities of interest” approach the government has adopted to track down criminals. According to Albert Gidari’s testimony before the House Judiciary Committee in May, “It is common … for the government to seek the location of the community of interest—that is, the location of persons with whom the target communicates.” ²⁷Hearing on Electronic Communications Privacy Act Reform before the H. Comm. on Judiciary’s Subcomm. on the Constitution, Civil Rights, and Civil Liberties, 111th Cong. (2010), statement of Albert Gidari, partner, Perkins Coie LLP, available at http://judiciary.house.gov/hearings/pdf/Gidari100505.pdf.

Calls have already begun for Congress to address location tracking. The Digital Due Process Coalition—including not only the ACLU but also groups such as the EFF and the American Library Association, leading academics, and major companies such as AT&T, Google, Microsoft, and Facebook—have called on Congress to require a warrant based on probable cause for all location tracking. ²⁸A full list of the members of the Digital Due Process Coalition can be found at http://www.digitaldueprocess.com.

The ACLU believes the appropriate standard for Congress to adopt is to require law enforcement agents to obtain a warrant and show probable cause for all forms of cell phone tracking. Cell tracking enables law enforcement agents to keep track of people around the clock, for as long as they like. This tracking, particularly in its more precise forms (although the distinction between forms of cell tracking appears to be collapsing as technology progresses), can reveal a quite intimate and revealing portrait of someone’s life. As the D.C. Circuit recently described in a decision holding that the government needs a warrant based on probable cause to track a vehicle via GPS, such surveillance can reveal if a person “is a weekly churchgoer, a heavy drinker, a regular at the gym, an unfaithful husband, an outpatient receiving medical treatment, an associate of particular individuals or political groups—and not just one such fact about a person, but all such facts.” ²⁹United States v. Maynard, 2010 WL 3063788, at *13 (holding that continuous GPS surveillance of an individual’s movements without a warrant violates his reasonable expectation of privacy). This is the sort of information that reasonable people expect and desire to keep private, and Congress should make clear that a warrant and probable cause is the minimum legal standard for all forms of cell phone tracking.