Governmental Tracking of Cell Phones and
Vehicles: The Confluence of Privacy,
Technology, and Law
Richard M. Thompson
Law Clerk
December 1, 2011
Congressional Research Service
7-5700
www.crs.gov
R42109
CRS Report for Congress
Pr
epared for Members and Committees of Congress

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Governmental Surveillance of Cell Phones and Vehicles

Summary
Technology has advanced considerably since the framers established the constitutional parameters
for searches and seizures in the Fourth Amendment. What were ink quills and parchment are now
cell phones and the Internet. It is undeniable that these advances in technology threaten to
diminish privacy. Law enforcement’s use of cell phones and GPS devices to track an individual’s
movements brings into sharp relief the challenge of reconciling technology, privacy, and law.
Beyond the Constitution, a miscellany of statutes and cases may apply to these tracking activities.
One such statute is the Electronic Communications Privacy Act of 1986 (ECPA), P.L. 99-508, 100
Stat. 1848 (1986), which protects individual privacy and governs the methods by which law
enforcement may retrieve electronic communications information for investigative purposes,
including pen registers, trap and trace devices, wiretaps, and tracking devices. The primary debate
surrounding cell phone and GPS tracking is not whether they are permitted by statute but rather
what legal standard should apply: probable cause, reasonable suspicion, or something less.
Legislation has been introduced in the 112th Congress that proposes to update, clarify, or, in some
instances, strengthen the privacy interests protected under the law and give law enforcement a
clearer framework for obtaining crucial crime-fighting information. In particular, Senator Ron
Wyden and Representative Jason Chaffetz introduced identical legislation, S. 1212 and H.R.
2168, entitled the Geolocational Privacy and Surveillance Act, or GPS bill, which would make it
unlawful for a service provider to disclose or law enforcement to intercept or use a person’s
location unless they obtained a warrant based upon probable cause or one of the limited
exceptions applies. Senator Patrick J. Leahy has introduced the Electronic Communications
Privacy Act Amendment Act of 2011 (S. 1011), which not only includes a warrant requirement
for geolocation information, but also overhauls and updates other provisions of federal electronic
surveillance law.
Congress is not the only branch confronting this tension between technology and privacy—the
Supreme Court has granted certiorari in United States v. Jones, 131 S. Ct. 3064 (2011), to
determine whether the Fourth Amendment’s protection against unreasonable searches and
seizures precludes the police from placing a GPS device on a person’s vehicle without a warrant.
Though the Court has dealt with similar issues in United States v. Knotts, 460 U.S. 276 (1983),
and United States v. Karo, 468 U.S. 705 (1984), in Jones, the Court has been asked to determine
what effect the prolonged, warrantless use of a tracking device has on a person’s privacy interest.
This report will briefly survey Fourth Amendment law as it pertains to the government’s tracking
programs. It will then summarize federal electronic surveillance statutes and the case law
surrounding cell phone location tracking. Next, the report will describe the GPS-vehicle tracking
cases and review the pending Supreme Court GPS tracking case, United States v. Jones. Finally,
the report will summarize the geolocation and electronic surveillance legislation introduced in the
112th Congress.

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Governmental Surveillance of Cell Phones and Vehicles

Contents
Introduction...................................................................................................................................... 1
Fourth Amendment and Privacy ...................................................................................................... 2
Federal Surveillance Statutory Framework ..................................................................................... 4
Electronic Communications Privacy Act (ECPA) ..................................................................... 4
Evidentiary Standards of Proof Under ECPA............................................................................ 7
Cell Phone Surveillance in the Courts ............................................................................................. 8
Third Circuit Approach.............................................................................................................. 9
Conflict in the Lower Courts ................................................................................................... 11
Hybrid Theory ......................................................................................................................... 12
Governmental Surveillance of Vehicles......................................................................................... 14
United States v. Knotts: Surveillance on Public Roadways ..................................................... 15
United States v. Karo: Surveillance on Private Property ......................................................... 15
GPS Tracking in the Seventh and Ninth Circuits .................................................................... 16
United States v. Jones: Supreme Court Review....................................................................... 16
Pending Legislation Before the 112th Congress............................................................................. 18
Electronic Communications Privacy Act Amendments Act of 2011 (S. 1011) ....................... 19
Geolocational Privacy and Surveillance Act (GPS Bill; S. 1212 and H.R. 2168)................... 20
Conclusion ..................................................................................................................................... 22

Contacts
Author Contact Information........................................................................................................... 22

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Governmental Surveillance of Cell Phones and Vehicles

Introduction
Technology has advanced considerably since the framers established the constitutional parameters
for searches and seizures in the Fourth Amendment. What were ink quills and parchment are now
cell phones and the Internet. It is undeniable that these advances in technology threaten to
diminish privacy. Law enforcement’s use of cell phones and GPS devices to track an individual’s
movements brings into sharp relief the challenge of reconciling technology, privacy, and law.
A miscellany of statutes and cases may apply to these tracking programs. One such statute is the
Electronic Communications Privacy Act of 1986 (ECPA),1 which protects individual privacy and
governs the methods by which law enforcement may retrieve electronic communications for
investigative purposes. ECPA addresses various means for conducting these investigations,
including pen registers, trap and trace devices, wiretaps, and tracking devices. The primary debate
surrounding statutory regulation of cell phone and GPS tracking is not whether they are
permitted, but rather what legal standard should apply: probable cause, reasonable suspicion, or
something less. More fundamentally, the Constitution sets a floor for permissible tracking
practices.
Legislation has been introduced in the 112th Congress that proposes to update, clarify, or, in some
instances, strengthen the privacy interests protected under the law and give law enforcement a
clearer framework for obtaining crucial crime-fighting information. In particular, Senator Ron
Wyden and Representative Jason Chaffetz introduced identical legislation, S. 1212 and H.R.
2168, the Geolocational Privacy and Surveillance Act (GPS bill), which would make it unlawful
for a service provider to disclose a person’s location unless law enforcement obtained a warrant
based upon probable cause or one of the limited exceptions applies. Senator Al Franken has
introduced the Location Privacy and Protection Act of 2011 (S. 1223)—similar to the GPS bill,
but which applies only to private, not governmental, actors. Senator Patrick J. Leahy has
introduced the Electronic Communications Privacy Act Amendment Act of 2011 (S. 1011), which
not only includes a warrant requirement for geolocation information, but also overhauls and
updates other provisions of federal electronic surveillance law.
Congress is not the only branch confronting this tension between technology and privacy—the
Supreme Court has granted certiorari in United States v. Jones, to determine whether the Fourth
Amendment’s protection against unreasonable searches and seizures precludes the police from
placing a GPS device on a person’s vehicle without a warrant.2 Though the Court has dealt with
similar issues in United States v. Knotts,3 and United States v. Karo,4 in Jones, the Court has been
asked to determine what effect the prolonged, warrantless use of a tracking device has on a
person’s privacy interest.
The use of geolocation information by private actors (e.g., telecommunication companies,
commercial service providers) also raises significant privacy concerns.5 As more computing

1 Electronic Communications Privacy Act of 1986, P.L. 99-508, 100 Stat. 1848 (codified as amended in scattered
sections of 18 U.S.C.).
2 United States v. Maynard, 615 F.3d 544, 555-56 (D.C. Cir. 2010), cert. granted sub nom. United States v. Jones, 131
S. Ct. 3064 (2011) (No. 10-1259) (oral arguments held on November 8, 2011).
3 United States v. Knotts, 460 U.S. 276 (1983).
4 United States v. Karo, 468 U.S. 705 (1984).
5 See CRS Report R41756, Privacy Protections for Personal Information Online, by Gina Stevens.
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moves to the “cloud,” concerns are raised as to what privacy protections consumers should be
accorded. The proposed legislation from the 112th Congress just described applies to both
government and private actors, and attempts to address some of these issues. However, an
analysis of the private use of this type of information is beyond the scope of this report.
This report will briefly survey Fourth Amendment law as it pertains to the government’s tracking
programs. It will then summarize federal electronic surveillance statutes and the case law
surrounding cell phone location tracking. Next, the report will describe the GPS-vehicle tracking
cases and review the Supreme Court GPS tracking case, United States v. Jones. Finally, the report
will summarize the geolocation and electronic surveillance legislation introduced in the 112th
Congress.
Fourth Amendment and Privacy
The fountainhead of privacy in the United States is the Fourth Amendment, which ensures that
“[t]he right of the people to be secure in their persons, houses, papers, and effects, against
unreasonable searches and seizures, shall not be violated....”6 For at least the past 50 years, this
provision has been subject to more litigation than any other in the Bill of Rights.7 This may come
as no surprise, considering the Fourth Amendment protects, as Justice Brandeis put it, “the right
to be let alone—the most comprehensive of rights and the right most valued by civilized men.”8
A recurrent theme flows through Fourth Amendment cases: criminals devise new ways to commit
crimes and evade the police; the police devise new ways to intercept communications and detect
criminal conduct; and the courts are left to sort out the constitutional from the not in these new
contexts. In 1928, for example, when police eavesdropped on the telephone conversations of Roy
Olmstead and his bootlegging conspirators, the Court refused to label this a violation of the
Constitution because the police had not physically trespassed on the defendants’ properties in
making the wiretaps.9 The Fourth Amendment protected a person’s property interest, the Court
held, not abstract things like his own voice.10 Also, the channel of communication, the telephone
wires, extended beyond the defendant’s home to the “whole world”—well beyond Olmstead’s
property interest.11
Almost 40 years later the Court changed course, radically altering the constitutional contours of
protected privacy by determining that “the Fourth Amendment protects people, not places.”12 In
Katz v. United States, the FBI eavesdropped on Katz’s conversation with an electronic device
after he had closed himself inside of a telephone booth. The Court found that act of closing
himself in a booth indicated Katz’s desire for privacy, and that the FBI had overstepped its

6 U.S. CONST. amend. IV.
7 1 WAYNE R. LAFAVE, SEARCH AND SEIZURE: A TREATISE ON THE FOURTH AMENDMENT IX (4th ed. 2004).
8 Olmstead v. United States, 277 U.S. 438, 478 (1928) (Brandeis, J., dissenting); see generally Samuel D. Warren &
Louis D. Brandeis, The Right to Privacy, 4 HARV. L. REV. 193 (1890). For a general overview of privacy law, see
Stevens, supra note 5.
9 Olmstead, 277 U.S. at 464-65.
10 Id.
11 Id. at 465.
12 Katz v. United States, 389 U.S. 347, 351 (1967).
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bounds when it listened to the contents of Katz’s conversation.13 The Court developed a new
standard—the reasonable expectation of privacy—to determine whether an act by the government
constitutes a search, thereby triggering a Fourth Amendment analysis. If a person has “exhibited
an actual (subjective) expectation of privacy” and it is one “that society is prepared to recognize
as ‘reasonable,’”14 then a search in the constitutional sense has occurred, and the court will
subject it to further analysis—usually, determining whether there was a warrant or whether an
exception to the warrant requirement applies. If, on the other hand, there was no reasonable
expectation of privacy, a warrantless search does not offend the Fourth Amendment.
Although Katz established that the contents of a conversation are accorded constitutional
protection, the Court did not extend this protection to information generated in making the
communication. This issue arose in Smith v. Maryland, in which the Court held that a person does
not have a reasonable expectation of privacy in the telephone numbers he dials.15 Michael Lee
Smith was a thief who robbed a young woman and then harassed her with obscene phone calls.
The police used a pen register (without a warrant) to record the numbers dialed from Smith’s
office. Based on the numbers he dialed, the police determined that Smith was calling the young
woman and later arrested him. In concluding that a search had not occurred, the Court reiterated
that a person has no legitimate expectation of privacy in information voluntarily given to third
parties—in this case, dialed numbers to the phone carrier.16
Generally, the Court has not applied the Fourth Amendment to surveillance conducted in public.17
Under this theory, the police are permitted to, without a warrant, fly a plane18 or a helicopter19 in
public airspace over a person’s private property to look for illegal activity; photograph
commercial property “exposed to visual observation from the air” from a plane that is “lawfully
within navigable airspace”;20 and attach a tracking device to a suspect’s vehicle to track its
movements while in public.21
Despite granting police wide latitude for searches occurring in public, the Court remains
solicitous of privacy in the home. In Karo v. United States, the Court held that monitoring the
presence of an item in a private residence through the use of a beeper violated the Fourth
Amendment rights of the residents, absent a valid warrant.22 Likewise, when police, without a
warrant, used thermal imaging on Danny Kyllo’s home to determine if he was using high-

13 Id. at 352-53.
14 Id. at 361 (Harlan, J., concurring).
15 Smith v. Maryland, 442 U.S. 735, 745-46 (1979).
16 Id. at 742; see also United States v. Miller, 425 U.S. 435, 442-43 (1976) (holding that financial statements and
deposit slips transmitted to bank were not protected from police inquiry because they had been turned over to a third
party).
17 Ric Simmons, Why 2007 Is Not Like 1984: A Broader Perspective on Technology’s Effect on Privacy and Fourth
Amendment Jurisprudence, 97 J. CRIM. L. & CRIMINOLOGY 531, 549 (2007).
18 California v. Ciraolo, 476 U.S. 207, 215 (1986) (holding that naked-eye search from airplane at 1,000 feet was not a
search).
19 Florida v. Riley, 488 U.S. 445, 451-52 (1989) (holding that surveillance from helicopter at 400 feet was not a
search).
20 Dow Chem. Co. v. United States, 476 U.S. 227, 238-39 (1986).
21 United States v. Knotts, 460 U.S. 276, 285 (1983). For a more detailed discussion of this case, see United States v.
Knotts: Surveillance on Public Roadways, infra p. 15.
22 United States v. Karo, 468 U.S. 705, 718 (1984) (upholding introduction of evidence found during search that was
based in part on impermissible beeper monitoring; warrant was independently sustainable by additional information).
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intensity heat lamps (usually an indication of growing marijuana), the Court again protected the
sanctity of the home, holding that information on activities within a home derived through sense-
enhancing technology outside of it was obtained in violation of the Fourth Amendment.23
The Constitution, however, is just one font of legal standards that balance privacy interests with
law enforcement needs. The Constitution is a floor, not a ceiling. Federal law (and state
constitutions and statutes) can provide more protection than the Constitution requires, but no less.
There are several comprehensive federal statutes that regulate the use of electronic surveillance—
in some instances Congress has seen fit to provide more protection than the constitutional floor,
while in others it has not.
Federal Surveillance Statutory Framework
As criminal enterprises harness new technologies to commit crime and evade police detection, the
police seek to avail themselves of the same technologies in an effort to effectively investigate and
prosecute criminal activities. Over the past several years, law enforcement has used cell phone
information obtained through service providers to monitor the movements of suspects.
Meanwhile, Congress has drawn and redrawn access standards under electronic communication
laws. Still, the debate over the use of cell location information is not “whether the government
can obtain cell site information. Rather, the issue is the standard it must meet before a court will
authorize such disclosure.”24
Electronic Communications Privacy Act (ECPA)
In response to Katz,25 Congress enacted Title III of the Omnibus Crime Control and Safe Streets
Act of 1968,26 which is the core of federal domestic surveillance law. Title III prohibits the
unauthorized use of surveillance techniques—for instance, bugging and wiretapping—by public
and private actors, but permits law enforcement to use such techniques in controlled and well-
defined circumstances.27 In 1986, Congress enacted the Electronic Communications Privacy
Act,28 which amended Title III, to prevent the “unauthorized interception of electronic
communications” and “update and clarify Federal privacy protections and standards in light of
dramatic changes in new computer and telecommunications technologies.”29 Congress sought to

23 Kyllo v. United States, 533 U.S. 27, 34 (2001) (holding that “obtaining by sense-enhancing technology any
information regarding the interior of the home that could not otherwise have been obtained without physical intrusion
into a constitutionally protected area, constitutes a search—at least where (as here) the technology in question is not in
general public use”) (citation omitted).
24 In re Application of the United States of America for an Order Authorizing the Disclosure of Prospective Cell Site
Information, No. 06-MISC-004, 2006 U.S. Dist. LEXIS 73324, *2 (E.D. Wis. October 6, 2006).
25 Matthew Minkle Werdegar, Lost? The Government Knows Where You Are: Cellular Telephone Call Location
Technology and the Expectation of Privacy, 10 STAN. L. & POL’Y REV. 103, 109 (1998).
26 Omnibus Crime Control and Safe Streets Act of 1968, P.L. 90-351, 82 Stat. 197.
27 1 JAMES G. CARR & PATRICIA L. BELLIA, THE LAW OF ELECTRONIC SURVEILLANCE §1.3 (2011).
28 Electronic Communications Privacy Act of 1986, P.L. 99-508, 100 Stat. 1848 (codified as amended in scattered
sections of 18 U.S.C.); see CRS Report R41733, Privacy: An Overview of the Electronic Communications Privacy Act,
by Charles Doyle; see also CARR & BELLIA, supra note 27, §1.14.
29 S.Rept. 99-541, at 1 (1986).
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balance the interests of law enforcement with the interest of citizen privacy.30 There are three
main titles in ECPA: the Wiretap Act,31 the Stored Communications Act,32 and the Pen
Register/Trap Trace Statute.33
The first title of ECPA amended Title III of the 1968 Omnibus Crime Control Act, the Wiretap
Act, to cover not only wire and oral communications, as originally enacted, but also “electronic
communications.”34 Under §2518, the government may obtain a wiretap order and listen to the
content of the calls (the words spoken) to and from a suspect only by demonstrating (1) probable
cause to believe that a crime was or is being committed; (2) the communication is relevant to that
crime; (3) normal investigative procedures have been tried but have failed; and (4) police believe
the location from which the communication is made is connected to the crime.35
The Pen Register/Trap Trace Statute is found in the second title of ECPA. A “pen register”36
records numbers dialed from a phone, and a “trap and trace device” captures the telephone
number of an incoming call.37 The pen register and trap-trace devices are the preferred
investigatory tools of law enforcement due to the modest standard for justifying their use: the
government need only show that “the information likely to be obtained by such installation and
use is relevant to an ongoing criminal investigation.”38 This standard, which is significantly less
than probable cause or reasonable suspicion, stems from the theory that a person has no
reasonable expectation of privacy in the phone numbers he dials.39 Under this statute, the court
wields no power of review but merely requires that the certificate be in proper form.40 Though
this standard is less demanding, there are limitations to the information that police may seek with
a pen register or trap-trace device: neither instrument may be used “in a manner so as to
constitute a ‘tracking device’” without first showing probable cause.41

30 Id. at 5; H.Rept. 99-647, at 19 (1986).
31 18 U.S.C. §§2510-2520 (2006).
32 18 U.S.C. §§2701-2712 (2006).
33 18 U.S.C. §§3121-3127 (2006).
34 18 U.S.C. §§2510-2520.
35 18 U.S.C. §2518.
36 18 U.S.C. §3127(3) (A “pen register” is defined as “a device or process which records or decodes dialing, routing,
addressing, or signaling information transmitted by an instrument or facility from which a wire or electronic
communication is transmitted.”).
37 18 U.S.C. §3127(4) (A “trap and trace device” is defined as “a device or process which captures the incoming
electronic or other impulses which identify the originating number or other dialing, routing, addressing, and signaling
information reasonably likely to identify the source of a wire or electronic communication, provided, however, that
such information shall not include the contents of any communication.”).
38 18 U.S.C. §3123(a)(1).
39 Smith v. Maryland, 442 U.S. 735 (1979).
40 See In re Application of the United States of America for an Order: (1) Authorizing the Installation and Use of a Pen
Register and Trap and Trace Device; (2) Authorizing the Release of Subscriber and Other Information; and (3)
Authorizing the Disclosure of Location-Based Services, Nos. 1:06-MC-6, 1:06-MC-7, 2006 WL 1876847, *2 (N.D.
Ind. July 5, 2006).
41 In re Applications of the United States of America for Orders Pursuant to Title 18, United States Code, Section
2703(d) to Disclose Subscriber Information and Historical Cell Site Information for Mobile Identification Numbers:
(XXX) XXX-AAAA, (XXX) XXX-BBBB, and (XXX) XXX-CCCC, 509 F. Supp. 2d 64, 68 (D. Mass. 2007) (citing
47 U.S.C. §1002(a)(2)(B) (2006)).
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The third title of ECPA is the Stored Wire and Electronic Communications and Transactional
Records Access Act, more commonly referred to as the Stored Communications Act (SCA).
Section 2703 of the SCA prescribes the manner in which service providers may divulge records
and contents of wire and electronic communications to the government.42 Under subsections (a)
and (b), if the government seeks the contents of a communication that has been in storage less
than 180 days, it must obtain a warrant (supported by probable cause) under Rule 41 of the
Federal Rules of Criminal Procedure.43 Under §2703(c), if the government seeks only “a record
or other information pertaining to a subscriber,”44 it can require the service provider to turn over
the documents if they “offer[] specific and articulable facts showing that there are reasonable
grounds to believe that the contents of a wire or electronic communication, or the records or other
information sought, are relevant and material to an ongoing criminal investigation.”45
The most significant provision of the SCA for purposes of cell location data is the definition of
“electronic communication.” This definition excludes “any communication from a tracking
device,”46 which is defined as “an electronic or mechanical device which permits the tracking of
the movement of a person or object.”47 In the courts that have confronted this issue, much hinges
on whether a cell phone should be categorized as a “tracking device.”48
In 1994, Congress enacted the Communications Assistance for Law Enforcement Act (CALEA),
which required communication providers to develop protocols for ensuring law enforcement
access to information for which it had lawful authorization.49 Congress authorized funding for
these service providers to assist in upgrading their systems.50 CALEA required
telecommunication carriers to ensure they had the ability to provide law enforcement “access to
call-identifying information.”51 It should be noted, however, that the text explicitly excluded
location information: “such call-identifying information shall not include any information that
may disclose the physical location of the subscriber (except to the extent that the location may be
determined from the telephone number)....”52

42 18 U.S.C. §§2703, 2702 (2006) (“A person or entity providing electronic communication service to the public shall
not knowingly divulge to any person or entity the contents of the communication while in electronic storage by that
service.”); see CARR & BELLIA, supra note 27, §1.17.
43 18 U.S.C. §2703(a); FED. R. CRIM. P. 41(d).
44 18 U.S.C. §2703(c).
45 18 U.S.C. §2703(d).
46 18 U.S.C. §2711 (2006) (cross-referencing 18 U.S.C. §2510 for definitions); 18 U.S.C. §2510(12)(C).
47 18 U.S.C. §3117 (2006).
48 Title I of ECPA references the use of tracking devices. 18 U.S.C. §3117(b); see also FED. R. CRIM. P. 41 (“After
receiving an affidavit or other information, a magistrate judge—or if authorized by Rule 41(b), a judge of a state court
of record—must issue the warrant if there is probable cause to search for and seize a person or property or to install and
use a tracking device.”) (emphasis added). Congress included §3117 to ensure that mobile tracking devices could be
used when a suspect crosses state lines. The Senate report states that this was merely a jurisdictional clarification that
was not intended to affect the legal standards required for tracking authorization. S.Rept. 99-541, at 10 (1986). Section
3117 broadly defines “tracking device” as “an electronic or mechanical device which permits the tracking of the
movement of a person or object.” 18 U.S.C. §3117(b). This definition is integral to understanding whether a warrant is
needed to obtain locational information from a cell phone; some courts treat cell phones as tracking devices, while
others do not.
49 Communications Assistance for Law Enforcement Act, P.L. 103-414, 108 Stat. 4279 (1994).
50 H.Rept. 103-827, at 10 (1994).
51 47 U.S.C. §1002(a)(2) (2006).
52 47 U.S.C. §1002(a)(2)(B).
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Evidentiary Standards of Proof Under ECPA
It is helpful to think of the requisite evidentiary proof required for disclosure of electronic
communications as a tiered system, ranging from highest (or most stringent) to lowest (or least
stringent).53 The most stringent is the Wiretap Act standard—the “super-warrant” requirement.54
Among other conditions, the Wiretap Act requires a detailed affidavit of the facts warranting the
search, the specific time and date of the proposed search, and an explanation of why other
investigatory methods are insufficient.55 Next are tracking devices, as defined in 18 U.S.C. §3117,
which may require a warrant (based upon probable cause) under Rule 41 of the Rules of Criminal
Procedure.56 Below that falls §2703(d) of the Stored Communications Act, which requires
“specific and articulable facts showing that there are reasonable grounds to believe that the
contents of a wire or electronic communication, or the records or other information sought, are
relevant and material to an ongoing criminal investigation.”57 As discussed below, the courts are
split on whether §2703(d) applies to historical records, real-time records, or both. Finally, the
lowest tier, contained in the Pen Register/Trap Trace statute, is a certification that the
“information likely to be obtained is relevant to an ongoing criminal investigation being
conducted by that agency.”58 Police need not present specific facts as the higher tiers require, but

53 This framework is described in In re Application for Pen Register and Trap/Trace Device With Cell Site Location
Authority, 396 F. Supp. 2d 747, 753 (S.D. Tex. 2005).
54 Orin S. Kerr, Internet Surveillance Law After the USA Patriot Act: The Big Brother That Isn’t, 97 NW. U. L. REV.
607, 630 (2003).
55 18 U.S.C. §2518 (2006).
56 18 U.S.C. §3117 (2006). Probable cause, as required for a wiretap or information from a tracking device, is the
highest level of evidentiary proof to conduct a search. It is rooted in the text of the Constitution, U.S. CONST. amend IV,
and the Court has reiterated time and again that law enforcement must obtain a warrant based upon probable cause
unless the investigation does not implicate a reasonable expectation of privacy or else falls within an established
exception. Katz v. United States, 389 U.S. 347, 357 (1967) (citations omitted). There are various formulations of this
standard, but it is said that “[p]robable cause exists where the facts and circumstances within their [the officers’]
knowledge and of which they had reasonably trustworthy information [are] sufficient in themselves to warrant a man of
reasonable caution in the belief that an offense has been or is being committed.” Brinegar v. United States, 338 U.S.
160, 175-76 (1949) (citation omitted) (internal quotation marks omitted). The Court later simplified this phrase by
requiring a “fair probability that contraband or evidence of a crime will be found in a particular place.” Illinois v.
Gates, 462 U.S. 213, 238 (1983).
57 18 U.S.C. §2703(d) (2006). “Specific and articulable facts” is comparable to the “reasonable suspicion” standard,
which was first announced in Terry v. Ohio, 392 U.S. 1, 30-31 (1968). Reasonable suspicion requires that the officer
“be able to articulate something more than an inchoate and unparticularized suspicion or hunch,” United States v.
Sokolow, 490 U.S. 1, 7 (1989) (internal quotation marks omitted), but instead has information that a “reasonably
prudent man in the circumstances would be warranted in the belief that his safety or that of others was in danger.”
Terry, 392 U.S. at 27.
58 18 U.S.C. §3122(b)(2) (2006). The standard for pen registers and trap and trace devices bears some resemblance to
the “special needs” doctrine, which covers cases “beyond the normal need of law enforcement.” Nat’l Treasury Emps.
Union v. Von Raab, 489 U.S. 656, 665 (1989) (balancing the “individual’s privacy expectations against the
Government’s interests to determine whether it is impractical to require a warrant or some level of individualized
suspicion in the particular context”). This reasonableness standard has been used in cases of drug tests for high school
students, Bd. of Educ. of Indep. Sch. Dist. No. 92 v. Earls, 536 U.S. 822, 838 (2002), and railroad employees, Skinner
v. Ry. Labor Execs.’ Ass’n., 489 U.S. 602, 633-34 (1989), and drunk driving checkpoints, Michigan Dep’t of State
Police v. Sitz, 496 U.S. 444, 455 (1990). But the Court has cabined off the use of this lowest standard to those few
limited instances; the Court declined to apply it to a drug interdiction checkpoint, City of Indianapolis v. Edmond, 531
U.S. 32, 48 (2000), and drug tests for birthing mothers, Ferguson v. City of Charleston, 532 U.S. 67, 86-87 (2001). This
balancing test is much easier to satisfy than probable cause or reasonable suspicion.
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merely must present the certification. This requirement has been described by one federal court as
a “low one.”59
The differences in these standards are important, as the debate in state and federal courts over cell
location information turns on which tier—or level of proof—the government must prove to obtain
the information; some courts require a showing of probable cause, while others permit an order
based on “specific and articulable facts.”
Cell Phone Surveillance in the Courts
Federal electronic surveillance law is a patchwork of terms and standards. Nowhere is this more
apparent than in the federal courts’ application of ECPA to government requests for cell site
location information.60 Policy arguments exist both for facilitating access and restricting it. The
government, on one hand, argues that “cell site information is an important investigatory tool
which is used ... to, among other things, help to determine where to establish physical
surveillence [sic] and to help locate kidnapping victims, fugitives, and targets of criminal
investigations.”61 Privacy proponents, on the other hand, want to ensure “Big Brother stays out of
your pocket” and argue that the government is trying to turn the cell phone system into a “vast
network for warrantless physical surveillance.”62

59 In re Application of the United States of America for an Order for Disclosure of Telecommunications Records and
Authorizing the Use of a Pen Register and Trap and Trace, 405 F. Supp. 2d 435, 439 (S.D.N.Y. 2005).
60 See Congressional Distribution Memorandum, Legal Standard for Disclosure of Cell-Site Information (CSI) and
Geolocation Information, by Gina Stevens, Alison Smith, and Jordan Segall (on file with CRS). The debate in the
federal courts centers around cell site location information, which is one of the two distinct methods for determining
the location of a cell phone. (A full description of cell phone technology is beyond the scope of this report, but can be
found at Marshall Brain et al., How Cell Phones Work, HOW STUFF WORKS (last visited October 20, 2011),
http://electronics.howstuffworks.com/cell-phone.htm). GPS, or Global Positioning System, is a system of 24 satellites
that constantly orbit Earth. In re Application of the United States of America for Historical Cell Site Data, 747 F. Supp.
2d 827, 831 (S.D. Tex. 2010). When hardware inside the cell phone receives signals from at least four of these
satellites, the handset can calculate its latitude and longitude to within 10 meters. Id. at 832. There are drawbacks to
GPS technology: the system is not fully operable when objects block its access. Note, Who Knows Where You’ve Been?
Privacy Concerns Regarding the Use of Cellular Phones as Personal Locators, 18 HARV. J. L. & TECH. 307, 308
(2004). Despite the accuracy of this technology, courts have yet to address whether GPS tracking can be used to locate
a cell phone’s location. Adam B. Merrill, Comment, Can You Find Me Now? The Federal Government’s Attempt to
Track Criminal Suspects Using Their Cell Phones, 43 ARIZ. ST. L. J. 591, 606 (2011).
The second method of determining the location of a cell phone is by triangulation, a process by which a cell phone’s
location can be determined from its communication with local cell towers. See In re Pen Register & Trap/Trace Device
with Cell Site Location Authority, 396 F. Supp. 2d 747, 751 (S.D. Tex. 2005). There are two distinct technologies used
to locate a cell phone through a network: time difference of arrival and the angle of arrival. Note, Who Knows Where
You’ve Been?, 18 HARV. J. L. & TECH. 307, 308 (2004). The time difference technology measures the time it takes for a
signal to travel from the cell phone to the tower. When multiple towers pick up this signal, an algorithm allows the
network to determine the phone’s latitude and longitude. Id. at 308-09. The angle of arrival technology uses the angles
at which a phone’s signal reaches a station. When more than one tower receives the signal, the network compares this
data the multiple angles of arrival and triangulates the location of the cell phone. Id. at 309.
61 In Re Application of the United States for an Order for Prospective Cell Site Location Information on a Certain
Cellular Telephone, 460 F. Supp. 2d 448, 452 (S.D.N.Y. 2006) (quoting Gov. Br. at 2).
62 Cell Tracking, ELECTRONIC FRONTIER FOUNDATION, https://www.eff.org/issues/cell-tracking (last visited October 19,
2011); see also Brian C. Davis, Note, An Un-Watchful Eye: How Courts Have Allowed Emerging Electronic
Surveillance Escape Fourth Amendment Protection, 46 NEW ENG. L. REV. (Forthcoming 2012) (on file with the New
England Law Review) (“[I]f the government decides to use these devices, they must comply with the safeguards
entrenched in the Fourth Amendment.”).
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Though these requests for cell site location information have become more frequent in the lower
courts, only one circuit has directly confronted the issue of cell location information. The Third
Circuit Court of Appeals decided in favor of the government, holding that the “specific and
articulable facts” standard of the Stored Communications Act (SCA) was sufficient to obtain cell
location information. Many magistrate judges, on the other hand, have rejected this approach,
instead requiring probable cause. At times, the outcome in the lower courts has been influenced
by whether the government was seeking historical versus prospective cell site information.63
Third Circuit Approach
In 2010, the Third Circuit confronted as a matter of first impression a government request for
historical cell location information.64 The government applied for a court order under the Stored
Communications Act to compel a cell phone service provider to produce a customer’s historical
cellular tower data relating to that customer’s location.65 In a lengthy opinion, the magistrate
judge had denied this request, concluding that an order of this type, whether historical or real-
time, could only be granted upon a showing of probable cause.66 The District Court, without
analysis, affirmed the magistrate judge’s opinion.67 The Third Circuit reversed, holding that the
magistrate judges have the discretion whether to require the government to show “specific and
articulable facts” under the Stored Communication Act or probable cause under a general warrant
theory, depending on whether access to this information under the lower “articulable facts”
standard would violate the Fourth Amendment.68
Before the lower court, the government primarily contended that a cell phone was not a tracking
device and thus cell location information could be obtained under the Stored Communications
Act.69 This proposition was crucial to the government’s argument because location information
from a “tracking device”70 cannot be sought under the Stored Communications Act.71 If this

63 Some cases hold that historical but not prospective information can be obtained under the Stored Communications
Act. See In re Application for Pen Register and Trap/Trace Device with Cell Location Authority, 396 F. Supp. 2d 747
(S.D. Tex. 2005); In re United States for an Order (1) Authorizing the Use of a Pen Register and a 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). Others hold that historical information and limited prospective information can be obtained under the
SCA. See In re Application of the United States of America for an Order: (1) Authorizing the Installation and Use of a
Pen Register and Trap and Trace Device, and (2) Authorizing Release of Subscriber and Other Information, 622 F.
Supp. 2d 411 (S.D. Tex. 2007). Finally, others permit access to both prospective and historical information. See In re
Application of the United States for an Order for Prospective Cell Site Location Information on a Certain Cellular
Telephone, 460 F. Supp. 2d 448 (S.D.N.Y. 2006).
64 The information sought in this case was not from a GPS device; the court was not asked nor did it take a position on
the use of GPS data, but merely answered the cell location information question. In re Application of the United States
of America for an Order Directing a Provider of Electronic Communication Service to Disclose Records to the
Government, 620 F.3d 304, 311 (3d Cir. 2010).
65 Id. at 305.

66 In re Application of the United States of America for an Order Directing Provider of Electronic Communication
Service to Disclosure Records to the Government, 534 F. Supp. 2d 585, 585-86 (W.D. Pa. 2008).
67 In re Application of the United States of America for an Order Directing Provider of Electronic Communication
Service to Disclose Records to the Government, No. 07-524M, 2008 U.S. Dist. LEXIS 98761 (W.D. Pa. September 10,
2008).
68 Application for Disclosure of Records, 620 F.3d at 319.
69 Application for Disclosure of Records, 534 F. Supp. 2d at 601.
70 18 U.S.C. §3117(b).
71 To be clear, the definition of “electronic communications” excludes “any communication from a tracking device,” 18
(continued...)
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argument failed, the government would be required to show probable cause. A tracking device,
the magistrate judge noted, is anything which “permits the tracking of movement of a person or
object.”72 She concluded that a cell phone undoubtedly constituted a “tracking device” because it
could locate a person to within 50 feet and continuously broadcasted information.73 She further
pointed out that “[b]y virtue of cell phone technology, law enforcement may now electronically
monitor our movements with as much—indeed, ofttimes more—scope and precision as by its
traditional methods of visual surveillance and/or installation of a ‘beeper.’”74
Because the cell phone was considered a tracking device, and the Stored Communications Act
excludes tracking devices from its reach, the magistrate judge concluded that the Stored
Communications Act could not govern this request, and therefore any retrieval of information
must be authorized under the normal warrant process as required by Rule 41 of the Federal Rules
of Criminal Procedure.75
On appeal from the district court, the government narrowed its focus, arguing that historical cell
location information (rather than both historical and prospective information) falls within the
Stored Communications Act. The Third Circuit agreed, reversed the lower courts, and held that
the Stored Communications Act’s intermediate “articulable and specific facts” standard applied.76
The government’s main contention was again that cell phones were not tracking devices, but,
further, that the location data was derived not from an “electronic communication,”77 but from a
“wire communication.”78 “‘Wire communication’ means any aural transfer made in whole or in
part through the use of facilities for the transmission of communications by the aid of wire, cable,
or other like connection between the point of origin and the point of reception....”79 The Third
Circuit accepted that the historical location information requested was “derived from a ‘wire
communication’ and does not itself comprise a separate ‘electronic communication.’”80 Even if a
cell phone was a tracking device excluded from “electronic communication” as described in
§2510, it would not matter, as tracking devices are not excluded from the definition of “wire
communication.”81 Relying on the phrase “may be issued” in §2703(d), the court concluded that
the decision whether to require a warrant or an order under the intermediate standard is

(...continued)
U.S.C. §2510(12)(C). The definition of “wire communications,” the other form of communications governed by the
Stored Communications Act, does not exclude communications from a tracking device. 18 U.S.C. §2510(1).
72 Application for Disclosure of Records, 534 F. Supp. 2d at 601 (quoting 18 U.S.C. §3117(b)).
73 Id. at 602.
74 Id.
75 Id. at 601.
76 Application for Disclosure of Records, 620 F.3d at 319.
77 ECPA defines “electronic communication” as “any transfer of signs, signals, writing, images, sounds, data, or
intelligence of any nature transmitted in whole or in part by a wire, radio, electromagnetic, photoelectronic or
photooptical system that affects interstate or foreign commerce.” 18 U.S.C. §2510(12).
78 Id. at 309.
79 18 U.S.C. §2510(1). “‘Aural transfer’ means a transfer containing the human voice at any point....” §2510(18).
Meanwhile, “electronic communication” does not include “any wire or oral communication....” §2510(12). “Oral
communication” means an utterance by a person with a justifiable expectation that the communication will not be
intercepted. §2510(2).
80 Application for Disclosure of Records, 620 F.3d at 310.
81 Id.
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discretionary—that is, a court can choose to require either a warrant or a court order based on the
lesser standard, depending on the facts.82
Conflict in the Lower Courts
Though the other circuit courts have yet to interpret the requests for cell phone location
information under the Stored Communications Act, the district courts, and in particular magistrate
judges, have written quite lengthy opinions on the issue, and have reached divergent conclusions.
For instance, the Southern District of Texas found unpersuasive the government’s stance that the
Stored Communications Act applied to its request for prospective or real-time cell location
information.83 The analysis, similar to that employed by the magistrate judge in the Third Circuit
case, begins with the definition of tracking device: the government argued that cell location
information did not fit the definition of tracking device—“an electronic or mechanical device
which permits the tracking of the movement of a person or [object]”84—since it did not provide
detailed location information. With the advance in cell phone technology, the court found this
argument wanting, as tracking was becoming very precise, and further because the definition of
tracking device does not differentiate between general and specific vicinity tracking.85 Holding
that a cell phone falls into the definition of “tracking device,” the court then analyzed each major
section of ECPA—the Pen Register/Trap Trace Statute, the Wiretap Act, and the Stored
Communications Act—to determine if any of the sections apply to cell location information.
The court dismissed this information as obtainable under the Pen Register Statute, noting that
Congress explicitly prohibited law enforcement from obtaining any location information under
this statute.86 Next, the court excluded the “super-warrant wiretap standard,” as the government
was not seeking to obtain the contents of the defendant’s conversations, but rather the location of
the caller.87 Finally, the court eliminated the Stored Communications Act based on the definitions
used in that act. First, the SCA must apply to an “electronic communication service.” “Electronic
communication service,” in turn, is defined as “any service which provides to users thereof the
ability to send or receive wire or electronic communications.”88 This location information cannot

82 Id. at 315. This interpretation of §2703(d) has not gone unscathed. Professor Orin Kerr regards this theory as “quite
unpersuasive.” Orin Kerr, Third Circuit Rules that Magistrate Judges Have Discretion to Reject non-Warrant Court
Order Applications and Require Search Warrants to Obtain Historical Cell-Site Records, THE VOLOKH CONSPIRACY,
http://volokh.com/2010/09/08/third-circuit-rules-that-magistrate-judges-have-discretion-to-reject-court-order-
application-and-require-search-warrants-to-obtain-historical-cell-site-records/ (last visited October 4, 2011). Kerr cites
to Ex parte United States, 287 U.S. 241 (1932), noting that “magistrate judges do not have discretion to decide whether
to issue court orders if the government satisfies the legal threshold.” Id. If the court were given discretion whether to
require a warrant, law enforcement could then forum shop for the more lenient magistrate. Id.
83 In re Application for Pen Register and Trap/Trace Device with Cell Site Location Authority, 396 F. Supp. 2d 747,
759, n.16 (S.D. Tex. 2005) (noting that historical cell location, as compared to prospective information, fits the
definition of transactional records covered by the Stored Communications Act).
84 Id. (citing 18 U.S.C. §3117(b) (2006)).
85 Id. at 755.
86 Id. at 757-58 (“With regard to information acquired solely pursuant to the authority for pen registers and trap and
trace devices ... such call identifying information shall not include any information that may disclose the physical
location of the subscriber (except to the extent that the location may be determined from the telephone number).”)
(emphasis in original) (quoting 47 U.S.C. §1002(a)(2)).
87 In re Application, 396 F. Supp. 2d at 758.
88 18 U.S.C. §2510(15).
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be from an electronic communication, the court concluded, as the definition specifically excludes
“tracking devices.” It also cannot be a “wire communication” because a wire communication
involves the “human voice.”89 Based on this logical sequence of interlocking definitions, the court
held that the SCA did not apply, and that the traditional warrant would be necessary.90
This analysis by the Southern District of Texas has been followed in a majority of jurisdictions.91
A minority of courts, on the other hand, have held that the government need not establish
probable cause, relying primarily on the hybrid theory.
Hybrid Theory
Under the hybrid theory, the government purports to have authority to obtain prospective cell
location information by combining provisions of the Pen Register Statute and the Stored
Communications Act.92 The Pen Register Statute was traditionally used by law enforcement to
record the dialed numbers for outgoing calls, and the trap and trace device to record incoming
calls.93 Pen registers are used not only for recording telephone numbers dialed but also to record
“signaling information,”94 language that was expanded by the USA PATRIOT Act in 2001.95 To
get approval under the Pen Register Statute, law enforcement need only show that the material
requested is relevant to an ongoing investigation.96 Although cell location information may fit
within this definition of “signaling information,” the Communications Assistance for Law
Enforcement Act (CALEA) of 1994 prohibits government access to location disclosing
information gained “solely pursuant to the authority for pen registers and trap and trace devices
...”97 Some courts rely on this “solely pursuant” language, or “exception clause,” to conclude that

89 Id. at 759.
90 Id. at 759, 765.
91 See In re Application of the United States for an Order for Prospective Cell Site Location Information on a Certain
Cellular Telephone, 2006 U.S. Dist. LEXIS 11747, *2 (S.D.N.Y. 2006); In re Application of the United States of
America for an Order Authorizing the Disclosure of Prospective Cell Site Information, 412 F. Supp 2d 947 (E.D. Wis.
2006); In re Application for Pen Register and Trap/Trace Device With Cell Site Location Authority, 396 F. Supp. 2d
294 (E.D.N.Y. 2005); In re Application of the United States of America for an Order (1) Authorizing the Use of a Pen
Register and a Trap and Trace Device and (2) Authorizing Release of Subscriber Information and/or Cell Site
Information, 384 F. Supp. 2d 562 (E.D.N.Y. 2005).
92 See Lisa M. Lindemenn, Note, From Cell to Slammer: Flaws in the Hybrid Theory, 53 ARIZ. L. REV. 663, 672
(2011).
93 18 U.S.C. §3127(3)-(4) (2006).
94 In re Application of the United States of America for an Order for Disclosure of Telecommunications Records and
Authorizing the Use of a Pen Register and Trap and Trace, 405 F. Supp. 2d 435, 438 (S.D.N.Y. 2005); 18 U.S.C.
§3127(3)-(4).
95 Uniting and Strengthening America by Providing Appropriate Tools Required to Intercept and Obstruct Terrorism
(USA PATRIOT ACT) Act of 2001, P.L. 107-56, §216(c)(2), 115 Stat. 272, 290.
96 18 U.S.C. §3123(a)(1) (2006).
97 47 U.S.C. §1002. This section reads, in pertinent part:
a telecommunications carrier shall ensure that its equipment, facilities, or services that provide a
customer or subscriber with the ability to originate, terminate, or direct communications are
capable of—...
(2) expeditiously isolating and enabling the government, pursuant to a court order or other
lawful authorization, to access call-indentifying information that is reasonably available to the
carrier—
(A) before, during, or immediately after the transmission of a wire or electronic
communication (or such later time as may be acceptable to the government); and
(continued...)
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the Pen Register/Trap Trace Statute may not be used as the sole means for obtaining cell location
information but can be used in conjunction with another statutory mechanism.
The hybrid theory looks to the Stored Communications Act as that other mechanism. Section
2703(c)(1) of the SCA provides that “a governmental entity may require a provider of electronic
communication service or remote computing service to disclose a record or other information
pertaining to a subscriber to or customer of such service.”98 Cell location information, the theory
goes, is information that pertains to a subscriber of cellular phone service.99 There is, however, a
roadblock to this theory: cell location information may appear to derive from an “electronic
communication” from a cell phone to a cell tower, but the act excludes any communication from
a tracking device from an “electronic communication.”
As was shown above, the definition of electronic communication excludes any “communication
from a tracking device.”100 Thus it may seem that cell phone tracking information cannot be
obtained under this theory. Courts accepting the hybrid theory, however, have pointed out that
“information on the location of cell towers is not the ‘service’ to which a cellular customer
subscribes. Instead, the user subscribes to the voice—and perhaps data—transmission capabilities
provided by the cellular carrier.”101 By focusing on the type of service the customer subscribes to,
and not the nature of the location information being relayed, the hybrid theory overcomes this
attack.
There is another hurdle to the hybrid theory: it is argued that the Stored Communications Act was
intended to cover only historical, not prospective information.102 To surmount this limitation, the
theory “circles back to the Pen/Trap statute ... [and] asserts that disclosure of cell site location
information is authorized by the SCA and can be collected in real time by virtue of the Pen/Trap
Statute.”103 With those concerns arguably overcome, the courts rely on §2703(d)’s “specific and
articulable facts” standard as controlling these requests.
The Eastern District of New York is not alone in accepting this theory,104 but most jurisdictions
have rejected it.105 Relying on legislative history, at least one court has noted that CALEA was
never intended to expand the reach of existing surveillance law.106

(...continued)
(B) in a manner that allows it to be associated to which it pertains,
except that, with regard to information acquired solely pursuant to the authority for pen
registers and trap and trace devices (as defined in section 3127 of Title 18), and such call
identifying information shall not include any information that may disclose the physical
location of the subscriber (except to the extent that the location may be determined from the
telephone number); (emphasis added).
98 18 U.S.C. §2703(c)(1) (2006).
99 In re Application for Disclosure of Telecommunications Records, 405 F. Supp. 2d at 444-45.
100 18 U.S.C. §2510(12) (2006).
101 In re Application for Disclosure of Telecommunications Records, 405 F. Supp. 2d at 446.
102 In re Application for Pen Register and Trap/Trace Device With Cell Site Location Authority, 396 F. Supp. 2d 747,
753 (S.D. Tex. 2005).
103 See Lindemenn, supra note 92, at 675.
104 See In re Application of the United States for an Order: (1) Authorizing the Installation and Use of a Pen Register
and Trap and Trace Device; and (2) Authorizing Release of Subscriber Information and/or Cell-Site Information, 411
F. Supp. 2d 678, 680 (W.D. La. 2006); In re Application of the United States for an Order for Prospective Cell Site
Location Information on a Certain Cellular Telephone, 460 F. Supp. 2d 448 (S.D.N.Y. 2006).
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A majority of the courts require law enforcement to obtain a warrant to access cell location
information. But it should be noted that there has been little appellate case law on cell phone
tracking, as there appears to be no incentive for defendants to raise the issue—ECPA does not
contain an exclusionary rule to prevent the admission of improperly obtained evidence.107 Thus
far, only the Third Circuit has directly ruled on this issue.
Governmental Surveillance of Vehicles
Like surveillance of cell phone location, the government uses GPS devices to track the location of
vehicles.108 Again, the courts have been asked to reconcile privacy interests and the needs of law
enforcement in an age of emerging technology. In contrast to the cell phone tracking cases, the
vehicle tracking cases have focused on constitutional and not statutory provisions.

(...continued)
105 In re Applications of the United States for Orders Authorizing the Disclosure of Cell Site Information, Nos. 05-403,
05-404, 05-407, 05-408, 05-409, 05-410, 05-411, 2005 WL 3658531, at *1 (D.D.C. October 26, 2005); In re
Application of the United States of America for an Order Authorizing the Installation and Use of a Pen Register a
Caller Identification System on Telephone Numbers [Sealed] and [Sealed] and the Production of Real Time Cell Site
Information, 402 F. Supp. 2d 597 (D. MD. 2005); In re Application of the United States for and Order for Prospective
Cell Site Location Information on a Certain Cellular Telephone, No. 06 CRIM. MISC. 01, 2006 WL 468300, at *2
(S.D.N.Y. February 28, 2006); In re Application of the United States of America for an Order Authorizing the
Disclosure of Prospective Cell Site Information, 412 F. Supp. 2d 947, 949 (E.D. Wis. 2006).
106 The Director of the Federal Bureau of Investigation (FBI) testified before Congress during its consideration of
CALEA, and insisted that the Pen Register/Trap Trace Statute has “‘nothing to do with’ the Stored Communications
Act, and that transactional information is ‘exclusively dealt with in chapter 121 of Title 18.’” In re Application, 396 F.
Supp. 2d 747, 753 (S.D. Tex. 2005) (“The government’s hybrid theory, while undeniably creative, amounts to little
more than a retrospective assemblage of disparate statutory parts to achieve a desired result.”); see Digital Telephony
and Law Enforcement Access to Advanced Telecommunications Technologies and Services: Joint Hearings Before the
Subcomm. on Technology and Law of the Senate Committee on the Judiciary and the Subcomm. on Civil and
Constitutional Rights of the House Committee on the Judiciary, 103rd Cong. 32 (statement of Director Freeh):
First, as is clearly set forth in the “purpose” section of the proposed legislation, the intent of the
legislation is to maintain existing technical capabilities and to “clarify and define the
responsibilities of common carriers *** to provide the assistance required to ensure that
government agencies can implement court orders and lawful authorizations to intercept the content
of wire and electronic communications and acquire call setup information under chapters 119 and
206 of Title 18 and chapter 36 of Title 50.” (emphasis added.) These chapters have nothing to do
with “transactional information” under our federal electronic surveillance and privacy laws. All
telecommunications “transactional” information is already protected by federal law and is
exclusively dealt with in chapter 121 of Title 18 of the United States Code (“stored wire and
electronic communications and transactional records access”). The proposed legislation does not
relate to chapter 121 of Title 18. Second, under federal law, Congress treats law enforcement’s use
of pen registers and dialing information differently than “transactional information”—such as
detailed telephone billing information.
107 Susan Freiwald, Cell Phone Location Data and the Fourth Amendment: A Question of Law, Not Fact, 70 MD. L.
REV. 681, 681 (2011).
108 CRS Report R41663, Law Enforcement Use of Global Positioning (GPS) Devices to Monitor Motor Vehicles:
Fourth Amendment Considerations, by Alison M. Smith.
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United States v. Knotts: Surveillance on Public Roadways
In United States v. Knotts, law enforcement attached a tracking device to a can of chloroform,
which was subsequently transported by the defendant in his car to a secluded cabin.109 The police
used the tracking device to learn of his location and then obtained a warrant based on this
information.110 When executing the search at the cabin, the police found a drug laboratory and
materials to make illegal drugs.111 The question presented was whether this monitoring violated
the defendant’s Fourth Amendment rights. The Supreme Court held that since a “person traveling
in an automobile on public thoroughfares has no reasonable expectation of privacy in his
movements from one place to another,” this type of monitoring did not violate the defendant’s
Fourth Amendment rights.112 The Court further stated that “scientific enhancement of this sort
raises no constitutional issues which visual surveillance would not raise.”113 According to Knotts,
if the police could theoretically track a suspect by the naked eye, they can use technology to do
the same thing.
United States v. Karo: Surveillance on Private Property
In United States v. Karo, the Court confronted the issue of “whether the monitoring of beeper in a
private residence, a location not open to visual surveillance, violates the Fourth Amendment
rights of those who have a justifiable interest in the privacy of the residence.”114 In Karo, Drug
Enforcement Administration (DEA) agents attached a tracking device to a can of ether and
tracked the can’s movements between multiple private residences and storage facilities.115 The
agents obtained a warrant to search a house rented by one of the defendants based on the
information derived from the tracking device.116 In concluding that use of the tracking device
constituted an unreasonable search, the Court first spelled out basic Fourth Amendment
principles: “private residences are places in which the individual normally expects privacy free of
governmental intrusion not authorized by a warrant, and that expectation is plainly one that
society is prepared to recognize as justifiable.”117
Unlike Knotts, the Court refused to accept the idea that the government “should be completely
free from the constraints of the Fourth Amendment to determine by means of an electronic
device, without a warrant and without probable cause or reasonable suspicion, whether a
particular article—or a particular person, for that matter—is in an individual’s home at a
particular time.”118 This case was distinguishable from Knotts because the “information obtained

109 United States v. Knotts, 460 U.S. 276, 278-79 (1983).
110 Id. at 279.
111 Id.
112 Id. at 281.
113 Id. at 285.
114 United States v. Karo, 468 U.S. 705, 714 (1984). Though the monitoring of the can of ether while in the private
residence was deemed unconstitutional, the warrant permitting police to search the residence where the contraband was
found was upheld because the police had sufficient untainted evidence independent of this monitoring. Id. at 721.
115 Id. at 708.
116 Id. at 710.
117 Id. at 714.
118 Id. at 716.
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in Knotts was ‘voluntarily conveyed to anyone who wanted to look.’”119 This gets back to the idea
that information a person voluntarily gives to another person—whether it is one’s public location
or telephone numbers dialed (think Smith v. Maryland)—is no longer private and no longer
afforded Fourth Amendment protection.
These two decisions left unresolved several lingering issues. Is the public versus private
distinction a bright-line rule? Is prolonged surveillance permissible so long as it could have been
done by visual surveillance? Does the use of advanced technology, such as GPS that enhances a
police officer’s senses, ever affect a Fourth Amendment analysis? The courts of appeals were
quickly asked to answer these questions.
GPS Tracking in the Seventh and Ninth Circuits
The Seventh and Ninth Circuits have held that the use of a GPS tracking device is not a search
afforded Fourth Amendment protection. In United States v. Garcia, Judge Posner analogized GPS
surveillance to “cameras mounted on lampposts or satellite imaging,”120 which are not considered
searches. The Seventh Circuit, however, was not confronted with the question as to whether all
tracking of vehicles on public ways is permissible, as the defendant did not raise this issue on
appeal. The court did say that the activity at issue, “namely following a car on a public street, ... is
unequivocally not a search within the meaning of the amendment.”121
In United States v. Pineda-Moreno, law enforcement entered Pineda-Moreno’s property and
attached a GPS device to his vehicle while it was parked in his driveway.122 Pineda-Moreno
challenged this monitoring not on the basis that the surveillance’s continuity exceeded Knotts in
scope, but rather that police were not permitted to use technology not in general public use as
described in Kyllo v. United States.123 Again, the Ninth Circuit rejected this argument, stating that
just because GPS made the police more effective at tracking the suspect does not mean that this
new form of tracking is unconstitutional; it refused to “equate[] efficiency with
unconstitutionality....”124
United States v. Jones: Supreme Court Review
The Supreme Court confronts the issue of government tracking once again in United States v.
Jones.125 Using an expired warrant, an FBI task force attached a GPS tracking device to Jones’s
Jeep Grand Cherokee while it was parked in a public lot in Maryland.126 For four weeks, the
government tracked the movements of Jones’s car with an accuracy to within 50-100 feet.127

119 Id. at 715.
120 United States v. Garcia, 474 F.3d 994, 997 (7th Cir. 2007).
121 Id.
122 United States v. Pineda-Moreno, 591 F.3d 1212, 1213 (9th Cir. 2010).
123 Id. at 1216.
124 Id.
125 United States v. Maynard, 615 F.3d 544 (D.C. Cir. 2010), cert. granted sub nom. United States v. Jones, 131 S. Ct.
3064 (2011) (No. 10-1259).
126 Brief for Respondent at 4, Jones, 131 S. Ct. 3064 (2011) (No. 10-1259), 2011 WL 4479076.
127 Brief for Petitioner at 3-4, Jones, 131 S. Ct. 3064 (2011) (No. 10-1259 ), 2011 WL 3561881.
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Based on this surveillance, the government retrieved over 2,000 pages of GPS data and was able
to track Jones to a stash house in Maryland where it ultimately found large amounts of cocaine.128
Prior to his trial, Jones filed a motion to suppress this evidence, which was denied except for
evidence obtained while his vehicle was parked in his garage.129
Jones appealed the constitutionality of both the installation and the subsequent surveillance of his
movements. The D.C. Circuit Court of Appeals did not address the installation issue, but instead
reversed on the basis that a prolonged, 24-hour surveillance without a warrant was a search, and
thus violated Jones’s Fourth Amendment right to privacy.130 The government argued this case was
on all fours with Knotts—that a “person traveling in an automobile on public thoroughfares has
no reasonable expectation of privacy in his movements from one place to another.”131 Jones
argued that the use of a GPS is much more pervasive than the beeper used in Knotts, and that
society is likely to recognize an expectation of privacy in the “pattern, or sum total, of an
individual’s daily activities.”132 The D.C. Circuit, accepting Jones’s argument, relied on Justice
Rehnquist’s dicta in Knotts that further Court oversight could be triggered under different
circumstances: “if [a] dragnet-type law enforcement practice[] as respondent envisions should
eventually occur, there will be time enough then to determine whether different constitutional
principles may be applicable.”133 Ultimately, the D.C. Circuit held that “[s]ociety recognizes
Jones’s expectation of privacy in his movements over the course of a month as reasonable, and
the use of the GPS device to monitor those movements defeated that reasonable expectation.”134
The Supreme Court has granted certiorari in Jones based upon two distinct questions:
(1)“Whether the warrantless use of a tracking device on respondent’s vehicle to monitor its
movements on public streets violated the Fourth Amendment”; and (2) “Whether the government
violated respondent’s Fourth Amendment rights by installing the GPS tracking device on his
vehicle without a valid warrant and without his consent.”135
As to the first question, much of the debate swirls around Justice Rehnquist’s dragnet passage in
Knotts, and whether he was referring to a program of mass surveillance of the public or prolonged
surveillance of a single person.136 In its brief, the government notes that the Court has used the
term “dragnet” to refer to “mass or widespread searches or seizures that are conducted without
individualized suspicion,” and should not be applied to surveillance of a single individual.137
Jones counters by noting that “‘dragnet’ can refer to ‘any system for catching a person, esp. a

128 Brief for Respondent, supra note 126, at 5.
129 United States v. Jones, 451 F. Supp. 2d 71, 88 (D.D.C. 2006).
130 United States v. Maynard, 615 F.3d 544, 555-56 (D.C. Cir. 2010).
131 Id. at 556.
132 Brief for Appellants at 65 n.239, Maynard, 615 F.3d 544 (D.C. Cir. 2010) (Nos. 08-3030, 08-3034), 2009 WL
3155141 (quoting Recent Case, Constitutional Law—Fourth Amendment—Seventh Circuit Holds that GPS Tracking is
Not a Search.—United States v. Garcia, 474 F.3d 994 (7th Cir. 2007), Reh’g and Suggestion for Reh’g Denied, No. 06-
2741, 2007 U.S. App. LEXIS 8397 (7th Cir. Mar. 29, 2007), 120 Harv. L. Rev. 2230, 2235 (2007)).
133 United States v. Knotts, 460 U.S. 276, 284 (1983).
134 Maynard, 615 F.3d at 563.
135 United States v. Maynard, 615 F.3d 544, 555-56 (D.C. Cir. 2010), cert. granted sub nom. United States v. Jones,
131 S. Ct. 3064 (2011) (No. 10-1259) (oral argument held on November 8, 2011).
136 It should be noted that this passage was dicta, meaning it is not controlling but merely persuasive.
137 Brief for Petitioner, supra note 127, at 34.
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fugitive.’”138 This dragnet theory should not be limited solely to mass surveillance, Jones argues,
but should cover prolonged, warrantless surveillance of one person. This question also implicates
the public-private dichotomy and whether use of sensory-enhancing technology can turn an
otherwise constitutionally permitted investigation into an unconstitutional search. The
government argues that the use of technology to collect information in public “does not make the
information any less public.”139 Based on that assumption, Knotts would apply and the GPS
surveillance would not be a search. Jones argues, to the contrary, that the government can obtain
information through GPS surveillance to a degree not feasible through visual surveillance. This
pattern information is more intrusive than a general search, thus interfering with an individual’s
reasonable expectation of privacy.
As to the second question, the D.C. Circuit did not reach the issue of whether the installation of
the GPS device on Jones’s Jeep was in and of itself a Fourth Amendment violation. The Ninth
Circuit has held that attachment of a GPS device on a vehicle while parked in the suspect’s
driveway was not a Fourth Amendment violation, as the car was parked in an area open to public
view and the suspect had not exhibited an expectation of privacy in the undercarriage of his car.140
Using similar reasoning, the Fifth Circuit held that the government’s attachment of a GPS device
to a car in a public place did not violate the suspect’s Fourth Amendment rights, as the car was
parked in plain view and the monitoring did not intrude on the suspect’s privacy.141 The First
Circuit, on the other hand, held that attaching a tracking device on a vehicle in a public parking
lot violates the Fourth Amendment.142
Pending Legislation Before the 112th Congress
Several bills have been introduced in the 112th Congress to amend federal surveillance laws.143 A
broad coalition of industry and privacy advocates including Apple, Google, AT&T, the American
Civil Liberties Union, and the Constitution Project—dubbed the Digital Due Process Coalition—
has joined to advocate for the passage of these measures.144 The Department of Justice also
advocates a clarification of existing surveillance law, but supports a lower standard that would
impose a lesser burden on law enforcement.145

138 Brief for Respondent, supra note 126, at 44 fn.8 (citing The Living Webster Encyclopedic Dictionary of the English
Language 300 (1975)).
139 Brief for Petitioner, supra note 127, at 19.
140 United States v. McIver, 186 F.3d 1119, 1126-27 (9th Cir. 1999).
141 United States v. Michael, 645 F.2d 252, 256 (5th Cir. 1981).
142 United States v. Moore, 562 F.2d 106, 112-113 (1st Cir. 1977).
143 Senator Al Franken has introduced the Location Privacy and Protection Act of 2011 (S. 1223)—similar to the GPS
bill, but which applies only to private, not governmental, actors. Because it only applies to private actors, and this
report focuses on governmental tracking, it will not be discussed.
144 DIGITAL DUE PROCESS, http://www.digitaldueprocess.com (last visited October 19, 2011). The group’s official
mission statement is “to simplify, clarify, and unify the ECPA standards, providing stronger privacy protections for
communications and associated data in response to changes in technology and new services and usage patterns, while
preserving the legal tools necessary for government agencies to enforce the laws, respond to emergency circumstances
and protect the public.” Id. at http://www.digitaldueprocess.org/index.cfm?objectid=99629E40-2551-11DF-
8E02000C296BA163.
145 The Electronic Communications Privacy Act: Government Perspectives on Protecting Privacy in the Digital Age,
112th Cong. (2011) (statement of James A. Baker, Assoc. Dep. Att’y Gen., Dep’t of Justice) (“Courts’ conflicting
interpretations of the statutory basis for obtaining prospective cell-site information have created uncertainty regarding
(continued...)
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Electronic Communications Privacy Act Amendments Act of 2011
(S. 1011)
On May 17, 2011, Senate Judiciary Chairman Patrick Leahy introduced legislation to update
federal surveillance law, with a focus on protecting consumer privacy.146 The Electronic
Communications Privacy Act Amendments Act of 2011 (S. 1011) would amend numerous
provisions of ECPA, including the Stored Communications Act.147
Section 5 would prohibit the government from accessing or using a device to acquire geolocation
information, unless the government obtains a warrant based upon probable cause or a court order
under Title I or Title IV of the Foreign Intelligence Surveillance Act (FISA) of 1978. There are
two exceptions to this requirement for court authorization: (1) to respond to an emergency call by
the user of the device; and (2) if the owner of the device gives express consent.
In an emergency, law enforcement may acquire geolocation information if it is determined that an
emergency situation exists that (1) involves immediate danger of death or serious bodily injury to
another person, conspiratorial activities characteristic of organized crime, or an immediate threat
to national security; (2) requires the accessing of geolocation before a court order could be
obtained; and (3) there are adequate grounds upon which a court order could be obtained. If law
enforcement accesses information based on this emergency exception, it must then apply for a
warrant within 48 hours of accessing the information. If a warrant is not obtained, this activity
must terminate immediately. If evidence is obtained in violation of this law, an exclusionary
clause will apply, which requires that this evidence not be admitted at trial.
Providers of electronic communication services, remote computing service, or geolocation
information service would be required to assist law enforcement with accessing the geolocation
information permitted under a lawfully obtained warrant. The service providers would in turn be
compensated for reasonable expenses incurred in providing such information. Providers are also
given immunity from suit for releasing information to the government pursuant to a request under
this act.
Section 6 would prohibit the government from requesting contemporaneous or prospective
geolocation information from a service provider unless the government met the same warrant
standards—that is, obtained a warrant under Rule 41 of the Federal Rules of Criminal Procedure.
This act, however, would allow law enforcement to access historical geolocation information
based upon a proof of “specific and articulable facts,” the same standard contained in the Stored
Communications Act.
The bill also permits law enforcement to retrieve general information about the target of the
search on a lesser showing, including the name and address of the subscriber, the times and

(...continued)
the proper standard for compelled disclosure of cell-location information, and some courts’ requirement of probable
cause has hampered the government’s ability to obtain important information in investigations of serious crimes.
Legislation to clarify and unify the legal standard and the proper mechanism for obtaining prospective cell-site
information could eliminate this uncertainty.”).
146 Though this bill targets both governmental and private, third-party use of geolocation information, the private use is
beyond the scope of this report.
147 S. 1011, 112th Cong., 1st Sess. (2011).
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durations of calls, and the means and source of payment, but expressly excluding location
information. Currently, the law permits access to a “record or other information pertaining to a
subscriber....”148 S. 1011 specifies which records could be accessed by law enforcement.
Geolocational Privacy and Surveillance Act (GPS Bill; S. 1212 and
H.R. 2168)
On June 15, 2011, Senator Ron Wyden and Representative Jason Chaffetz introduced companion
bills, the Geolocational Privacy and Surveillance Act, or GPS bill.149 The GPS bill would clarify
and establish the standards the government must meet to monitor an individual’s movements.
Under the GPS bill, law enforcement’s sole means for acquiring geolocation information would
be pursuant to a warrant under Rule 41 of the Federal Rules of Criminal Procedure or the Foreign
Intelligence Surveillance Act (FISA) of 1978.150 It would appear that the Stored Communications
Act or the Pen Register/Trap and Trace Act would no longer be mechanisms for acquiring this
information.
The bill contains a broad prohibition against the disclosure or use of geolocation information.151
Specifically, it makes it unlawful for any person152 to (A) intentionally intercept geolocation
information pertaining to another person; (B) intentionally disclose geolocation information
pertaining to another person when it is known that information was obtained in violation of the
act; (C) intentionally use any geolocation information knowing that the information was obtained
in violation of the act; or (D) intentionally disclose information that was lawfully obtained under
the act, but not authorized to be released to third parties.153
There are several exceptions to the prohibition against the use of geolocation information.
Providers of geolocation information service154 may intercept, use, or disclose geolocation
information in the normal course of business when it is a “necessary incident to the rendition of
service or to the protection of the rights or property of the provider of that service.” The service
providers, however, shall not randomly monitor customers except to service their systems.

148 18 U.S.C. §2703(c).
149 S. 1212, H.R. 2168, 112th Cong., 1st Sess. (2011).
150 S. 1212, §5.
151 “Geolocation information” is defined as “any information, that is not the content of a communication, concerning
the location of a wireless communication device or tracking device (as that term is defined section 3117) that, in whole
or in part, is generated by or derived from the operation of that device and that could be used to determine or infer
information regarding the location of the person.” S. 1212, §2601(4). “Geolocation information” covers information
from both GPS tracking and tracking via cell site location information.
152 The bill prohibits use of this information by “any person” (e.g., individuals, telecommunications companies, Internet
service providers, website operators, etc.), and not solely government actors. However, private use of geolocation
information is beyond the scope of this report; this analysis of S. 1212 is limited to government access to geolocation
information.
153 S. 1212, §2602(a)(1). Currently there is no broad federal prohibition against the use of geolocation information.
154 “Geolocation information service” is defined as “the provision of a global positioning service or other mapping,
locational, or directional information service to the public, or to such class of users as to be effectively available to the
public, by or through the operation of any wireless communication device, including any mobile telephone, global
positioning system receiving device, mobile computer, or other similar or successor device.” S. 1212, §2601(5).
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There is also an exception for surveillance conducted for national security purposes. Any agent or
officer of the United States is permitted to conduct surveillance as authorized under the Foreign
Intelligence Surveillance Act of 1978.
There are two consent provisions in the bill. First, it is not unlawful to intercept geolocation
information of a person if that person gives prior consent to such interception. Even if consent is
given, however, the information cannot be used for purposes of committing a criminal act in
violation of the Constitution or laws of the United States. Second, parents can consent to law
enforcement use of the information if a child becomes missing.
In cases of emergency, law enforcement or emergency responders are permitted to use
geolocation information to respond to a person requesting assistance (i.e., a 911 call).155 Also, the
police may use this information “in circumstances in which it is reasonable to believe that the life
or safety of the person is threatened, to assist the person.” If a phone is stolen or taken by fraud,
police are permitted to use geolocation information to locate the phone so long as the owner of
the phone consents to such use.
Police may use geolocation information if they obtain a warrant in accordance with Federal Rule
of Criminal Procedure 41 or as otherwise permitted under the Foreign Intelligence Surveillance
Act of 1978. This would codify the practice of federal courts that are currently requiring a warrant
based upon probable cause to obtain geolocation information, and would require courts that
instead have been relying on the Stored Communications Act’s standard of “specific and
articulable facts” to follow the majority warrant approach. To permit this change, the act would
amend Rule 41 to include geolocation information in the list of items subject to the warrant
requirement.
The United States Attorney General and the states’ Attorneys General are permitted to intercept
geolocation information without a warrant if they (1) reasonably believe that an emergency
situation exists, which can include an immediate danger of death or serious physical injury to any
person, conspiratorial activities threatening the national security interest, and conspiratorial
activities characteristic of organized crime; (2) there are grounds in which an order could be
entered to authorize such interception; and (3) an application is then requested within 48 hours
after the interception occurs.
The GPS bill contains an exclusionary rule, meaning no evidence acquired in violation of the act
may be received in evidence in any trial or other judicial proceeding. This is different from
ECPA, which does not contain an exclusionary rule. In addition to this exclusionary remedy, any
person whose geolocation information is intercepted may seek civil remedies. The person may
seek equitable remedies, damages (money), and reasonable attorneys fees and litigation costs.
The damages would be the greatest of (1) whatever the actual damages are to the injured party,
and any profits the violator may have made from the violation; (2) $100 a day for each day the
entity is in violation of the act; or (3) $10,000. There is a complete defense, however, against any
civil and criminal liability if the person believed in good faith that his interception or use of a
person’s geolocation was permitted under this act. There is also a two-year statute of limitation
for such claims. If it is determined that a person willfully or deliberately violated the act, the
government is permitted to take disciplinary action against him.

155 Unlike landline phones in a person’s house, the police can only determine a cell phone caller’s location either by the
caller telling the police where he is located, or by using the geolocation information from the phone.
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Section 4 of the GPS bill would amend 18 U.S.C. §1309(h), which criminalizes fraudulently
obtaining a person’s phone records, to include geolocation information to the types of records
subject to this law. Within 180 days after enactment of this act, the United States Sentencing
Commission would be required to amend the sentencing guidelines to take into account this
revision of §1309.
Conclusion
Congress, the courts, and the people will continue to grapple with “what limits there are upon
[the] power of technology to shrink the realm of guaranteed privacy.”156 Some observers believe
that ECPA has lived its useful life and should be amended to remain effective. One commentator
notes that the “changes in modern technology and shifting security concerns ... result in
ambiguous, overlapping guidance in the area of cell phone tracking.”157 Several Members of
Congress have introduced legislation to mend this perceived problem, and overhaul the current
federal surveillance regime. The Supreme Court has also been asked to weigh in on this debate
about the convergence of law and technology in the form of GPS tracking of a person’s car. These
cases and legislation have the potential to significantly impact the relationship among law,
privacy, and technology.

Author Contact Information

Richard M. Thompson

Law Clerk
rthompson@crs.loc.gov, 7-8449



156 Kyllo v. United States, 533 U.S. 27, 34 (2001).
157 Kevin McLaughlin, The Fourth Amendment and Cell Phone Location Tracking: Where are We?, 29 HASTINGS
COMM. & ENT. L. J. 421, 428 (2007).
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