MAY CONTAIN LAW ENFORCEMENT SENSITIVE INFORMATION-DRAFT

ELECTRONIC 

MONITORING

Draft National 

Standard for Offender 

Tracking Systems 

Addresses Common 

Stakeholder Needs

Report to the Ranking Member, 

Subcommittee on Oversight, Committee 

on Science, Space, and Technology, 

House of Representatives

October 2015

GAO-16-10

United States Government Accountability Office
Highlights of GAO-16-10, a report to the 

Ranking Member, Subcommittee on 

Oversight, Committee on Science, Space, and 

Technology, House of Representatives

October 2015 

ELECTRONIC MONITORING

Draft National Standard for Offender Tracking 

Systems Addresses Common Stakeholder Needs

Why GAO Did This Study

OTS is an electronic monitoring 

technology consisting of hardware, 

such as an ankle bracelet, used for 

collecting Global Positioning System 

(GPS) signals to determine an 

individual’s location, and software for 

analyzing data collected from the 

hardware device. While demand for 

GPS-based electronic monitoring 

devices has increased, there are 

currently no standards that OTS 

devices are required to meet. In 2009, 

NIJ initiated development of a 

voluntary OTS standard and 

companion guide, which is expected to

be published no later than March 2016.

GAO was asked to review NIJ’s 

approach for developing the OTS 

standard. 

This report examines the extent to 

which (1) NIJ collaborated with 

stakeholders in developing the 

standard, and (2) the standard and 

guide address stakeholder needs and 

challenges. GAO analyzed NIJ’s draft 

OTS standard, companion guide, and 

standard development process. To 

obtain perspectives on the standard 

development process and OTS needs 

and challenges, GAO interviewed 

stakeholders including NIJ officials, 

practitioners and experts who 

developed the standard, criminal 

justice and victims’ associations, 

manufacturers, and officials from a 

nongeneralizable sample of 10 criminal 

justice agencies that employ OTS. 

GAO selected the 10 criminal justice 

agencies based upon a combination of 

factors, including ensuring a range of 

federal, state, and local jurisdictions, 

among other things.

What GAO Found

The National Institute of Justice (NIJ) collaborated with a variety of criminal 

justice and technical experts to develop a draft standard for offender tracking 

systems (OTS), but earlier involvement of manufacturers could have expedited 

its development. For example, the committee that developed the draft standard 

included practitioners spanning all levels of government and program areas such 

as pretrial, probation, and parole services and technical experts with 

backgrounds in developing test methods for performance standards. NIJ invited 

manufacturers to provide input through a workshop held in May 2011 and two 

subsequent public comment periods. GAO found that earlier and ongoing 

involvement of OTS manufacturers could have better informed and facilitated 

development of the OTS standard by, for example, providing insights on OTS 

capabilities and limitations at the outset. Coordination has improved since 2012, 

and manufacturers’ major concerns have been addressed. 

Global Positioning System (GPS) Offender Tracking System

NIJ’s draft OTS standard and guide address many common stakeholder needs 

and challenges. The draft standard includes requirements for common 

operational and circumvention detection needs. For example, requirements for 

location accuracy and the ability to provide alerts when an offender tries to 

remove the device or is at a prohibited location are included in the standard. In 

addition, the draft guide provides information and guidance related to challenges

identified by the criminal justice agencies GAO met with as well as other 

considerations for implementing an OTS program. These challenges include

• misconceptions among the public and victims that OTS allows agencies to

prevent bad behavior before it happens;

• developing appropriate protocols to respond to OTS alerts, such as those for

tampering with the tracking device; and

• workload issues, such as whether there is sufficient staff or resources to

respond to OTS alerts 24 hours a day, 7 days a week.

In recognition of the range of agencies, resources, and objectives of offender 

tracking, the guide provides information and guidance, and does not offer “one

size fits all” solutions. 

View GAO-16-10. For more information, 

contact David C. Maurer at (202) 512-8777 or 

maurerd@gao.gov. 

United States Government Accountability Office
Letter 1

Background 6

NIJ Collaborated with a Variety of Stakeholders, but Earlier 

Manufacturer Involvement Could Have Expedited Development 

of the OTS Standard 13

Draft OTS Standard and Companion Guide Address Many 

Common Needs and Challenges Identified by Stakeholders 17

Agency Comments and Our Evaluation 30

Appendix I Operational and Circumvention Detection Needs Addressed in 

NIJ’s Draft Offender Tracking Standard 32

Appendix II GAO Contact and Staff Acknowledgments 34

Tables

Table 1: Offender Tracking System (OTS) Features to Mitigate 

Global Positioning System (GPS) Signal Reception Issues 30

Table 2: Comparison of Selected Operational and Circumvention 

Detection Needs to Draft Offender Tracking System 

Standard Minimum Performance Requirements 32

Figures

Figure 1: Methods for Supervising and Monitoring Offenders 7

Figure 2: Example of an Offender Tracking System Ankle Bracelet 9

Figure 3: Global Positioning System (GPS)–Based Offender 

Tracking System 10

Figure 4: DOJ Organization for OTS Standard Development 11

Figure 5: Standard Development and Maintenance Process 12

Figure 6: Development Timeline 14

Figure 7: Example of Inclusion and Exclusion Zones 19

Figure 8: Examples of Different Alert Response Models 27

Contents

Page i GAO-16-10 Electronic Monitoring
Abbreviations:

ANSI American National Standards Institute

AWG Advisory Working Group

BJS Bureau of Justice Statistics

DOJ United States Department of Justice

GPS Global Positioning System

NIJ National Institute of Justice

NIST National Institute of Standards and Technology

OJP Office of Justice Programs

OMB Office of Management and Budget

OTS Offender Tracking System

PMBOK® 

Guide A Guide to the Project Management Body of Knowledge

STC Special Technical Committee

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Page ii GAO-16-10 Electronic Monitoring
441 G St. N.W.

Washington, DC 20548

October 26, 2015 

The Honorable Donald S. Beyer, Jr.

Ranking Member

Subcommittee on Oversight

Committee on Science, Space, and Technology

House of Representatives

Dear Mr. Beyer:

Since 1996, criminal justice agencies have been monitoring the location 

of individuals with mobile devices. Prior to the advent of electronic 

monitoring with Global Positioning System (GPS) technology, criminal 

justice agencies’ methods for supervising individuals were limited to 

selected site location tracking (e.g., house arrest) and manual methods 

such as in-person visitation. Demand for and use of GPS-based 

electronic monitoring devices for tracking criminal offenders, also known 

as offender tracking systems (OTS), has increased in large part because 

of numerous legislative mandates, according to the Department of 

Justice’s (DOJ) National Institute of Justice (NIJ). For instance, NIJ 

reports that by 2010, 33 states had enacted legislation requiring OTS to 

track the location of sex offenders. According to 2012 Bureau of Justice 

Statistics (BJS) surveys of probation and parole agencies in the 50 states, 

the federal system, and the District of Columbia, over 31,600 adults on 

probation or parole were supervised with GPS technology.1

1

See Department of Justice, Bureau of Justice Statistics (BJS), Annual Parole Survey 

2012, (Ann Arbor, Michigan: Inter-university Consortium for Political and Social Research, 

October 2014); and Department of Justice, Bureau of Justice Statistics, Annual Probation 

Survey 2012, (Ann Arbor, Michigan: Inter-university Consortium for Political and Social 

Research, September 2014). This reflects the number of probationers or parolees that 

were tracked by GPS from January 1 through December 31, 2012, which is the most 

recent data reported by BJS. States in which the number of probationers supervised with 

GPS was not known include Alaska, Delaware, Idaho, Illinois, Kansas, Maine, Maryland, 

Minnesota, Nebraska, New Mexico, New York, Oklahoma, Pennsylvania, Rhode Island, 

Texas, and Utah. States in which the number of parolees supervised with GPS was not 

known include Alaska, Delaware, Idaho, Maryland, New Mexico, Oklahoma, 

Pennsylvania, and Utah. Also, not included are types of individuals who are supervised 

with GPS, such as pretrial defendants and juvenile offenders. 

Letter

Page 1 GAO-16-10 Electronic Monitoring
While demand for GPS-based electronic monitoring devices has 

increased, there are currently no standards that OTS devices are required 

to meet. For example, while users expect OTS devices to report location 

information, there is currently no minimum performance requirement for 

how accurate the location information must be. Absent a standard with 

minimum performance requirements, criminal justice agencies across the 

nation have relied on vendor assertions on performance and, at times, 

their own field testing of equipment to inform purchases.

In fiscal year 2006, a technology working group sponsored by DOJ’s NIJ 

identified the development of a standard for OTS technology as a high 

priority. The purpose of the OTS standard is to ensure OTS devices meet 

certain minimum performance requirements. In fiscal year 2009, NIJ 

directed funding to develop an OTS standard and a companion guide.2

Development of the standard and guide remains an ongoing effort. NIJ 

estimates that it will publish the standard by the end of calendar year 

2015, and no later than March of 2016. Use of the OTS standard is to be 

on a voluntary basis. OTS device manufacturers are to independently 

decide whether to comply with the voluntary standard by submitting their 

devices for testing and certification. Likewise, stakeholders, such as 

criminal justice agencies across the United States, are to individually 

decide whether to require compliance with the standard when acquiring 

new OTS technologies.

You asked us to review NIJ’s approach for developing the OTS standard 

and expressed questions about public safety. This report addresses the 

following questions:

1. To what extent has NIJ collaborated with stakeholders in developing

the OTS standard?

2. To what extent have the OTS standard and companion guide

incorporated stakeholder needs and addressed potential challenges?

To assess the extent to which NIJ collaborated with stakeholders in 

developing the OTS standard, we reviewed federal laws such as the 

National Technology Transfer and Advancement Act of 1995. The act 

2

NIJ also produced two additional companion documents: (1) OTS Certification Program 

Requirements, specifying requirements that must be satisfied to act as a product 

certification body; and (2), OTS Refurbishment Service Program Requirements, specifying 

requirements for certification bodies certifying refurbishing services performed on OTS. 

Page 2 GAO-16-10 Electronic Monitoring
generally states, with certain exceptions, that all federal agencies and 

departments shall use technical standards that are developed or adopted 

by voluntary consensus standard bodies, using such technical standards 

as a means to carry out policy objectives or activities determined by the 

agencies and departments.3 In addition, we reviewed Office of 

Management and Budget Circular A-119, which establishes policies 

consistent with the act to improve the internal management of executive 

branch agencies.4 In addition, we reviewed NIJ procedures on the 

development and use of standards. We examined the OTS standard 

development process NIJ has implemented by obtaining its records of 

activity and meeting with program officials involved in the development 

process. We compared NIJ’s development process for the OTS standard 

as applicable against the American National Standard Institute’s (ANSI) 

Essential Requirements, to understand whether NIJ’s process was 

consistent with accepted practices. ANSI is a well-established 

organization that accredits leading standard development organizations, 

such as Underwriters Laboratories Incorporated, and determines approval 

of individual standards. We further looked at A Guide to the Project 

Management Body of Knowledge’s stakeholder and collaboration 

practices to assess whether NIJ had followed practices for effectively 

involving stakeholders.5

We reviewed the timing, duration, and level and nature of stakeholder 

involvement. We also interviewed individuals appointed by DOJ to serve 

on the Advisory Working Group (AWG), which is charged with reviewing 

the standard. More specifically, we interviewed AWG members from the 

following organizations: the American Probation and Parole Association, 

American Correctional Association, National Sheriffs’ Association, and the 

U.S. Department of Homeland Security.6 Additionally, we interviewed 

3

Pub. L. No. 104-113, 110 Stat. 775 (1996). 

4

Office of Management and Budget (OMB), Circular No. A-119: Federal Participation in 

the Development and Use of Voluntary Consensus Standards and in Conformity 

Assessment Activities, (Washington, D.C.: February 10, 1998).

5

American National Standards Institute, ANSI Essential Requirements: Due process 

requirements for American National Standards, (New York: January 2015). Project 

Management Institute, A Guide to the Project Management Body of Knowledge (PMBOK® 

Guide), Fifth Ed. (2013). PMBOK is a trademark of the Project Management Institute, Inc. 

6

We were not able to identify and interview any involved official(s) with the International 

Association of Chiefs of Police, the remaining AWG member according to the draft OTS 

standard. 

Page 3 GAO-16-10 Electronic Monitoring
members of the Special Technical Committee (STC), which is charged 

with writing the standard and includes criminal justice practitioners from 

federal, state, and local levels of government as well as technical experts 

with experience in developing laboratory testing methods.

Given its role in federal standard development and level of technical 

expertise, we met with officials from the National Institute for Standards 

and Technology to assess their interaction with NIJ, involvement in the 

development process, and their perspective on NIJ’s process. In addition, 

we met with victims’ groups and OTS manufacturers to understand their 

perspectives on the likely effects of the standard and their involvement in 

the standard’s development process. Specifically, we met with 

representatives from the National Center for Victims of Crime, the 

National Coalition Against Domestic Violence, the National Organization 

for Victim Assistance, and the National Sexual Violence Resource Center. 

We selected the victims’ groups based upon recommendations from the 

American Probation and Parole Association, in response to our request to 

identify groups that represent communities’ concerns over the safety and 

protection of individuals affected by sexual and violent criminal offenses. 

We also met with representatives from the following OTS manufacturers: 

BI Incorporated, Satellite Tracking of People LLC, and Sentinel Offender 

Services LLC. We selected these manufacturers based upon their having 

submitted comments on the draft OTS standard. Further, these 

manufacturers provide equipment and services to the agencies that we 

interviewed, which included a range of jurisdiction types and sizes as 

discussed further below. The information we obtained from these 

organizations cannot be generalized, but provides perspectives and 

insights on NIJ’s process for developing the OTS standard.

To address the second objective, we selected a nonprobability sample of 

10 criminal justice agencies and analyzed the extent to which their OTS 

needs and challenges were addressed in NIJ’s draft OTS standard and 

the draft companion document, the Criminal Justice Offender Tracking 

System Selection and Application Guide (the guide).7 In recognition that 

the standard is meant to address a range of criminal justice OTS uses, 

7

See Department of Justice, National Institute of Justice, Criminal Justice Offender 

Tracking System Standard, NIJ Standard-1004.00, Draft for Public Comment (December 

2013); and Department of Justice, National Institute of Justice, Criminal Justice Offender 

Tracking System Selection and Application Guide, NIJ CR-1004.00.00 Draft for Public 

Comment (December 2013).

Page 4 GAO-16-10 Electronic Monitoring
we selected the 10 agencies based upon a combination of factors, 

including ensuring a range of federal, state, and local jurisdictions; 

geographic location; size; and types of offenders monitored. The 10 

agencies are the California Department of Corrections and Rehabilitation; 

Colorado Department of Corrections; DeKalb County, Georgia, Sheriff’s 

Office; Denver Community Corrections; Florida Department of

Corrections; Leon County [Florida] Office of Intervention and Detention 

Alternatives; Georgia Department of Corrections; Los Angeles County 

California Probation Department; the Department of Homeland Security’s 

Immigration and Customs Enforcement agency; and the U.S. Courts’ 

Probation and Pretrial Services System. To identify the selected 

agencies’ OTS needs, we reviewed their OTS contractual documents, 

such as statements of work, and OTS program procedures. At the time of 

our review, 1 of the 10 selected agencies was in the process of 

documenting its OTS needs. We therefore omitted this agency from the 

analysis of OTS performance requirements. We identified the range of 

performance requirements across the remaining 9 agencies and 

compared them against selected requirements in the draft OTS standard 

to determine the extent to which the draft standard addressed their 

needs. We also interviewed program officials and criminal justice officers 

responsible for supervising offenders from all 10 selected agencies to 

discuss their needs and identify any challenges they experience.8 The 

information we obtained from these agencies cannot be generalized to all 

criminal justice agencies, but offers insight into the range of OTS needs 

and challenges agencies may have.

We conducted this performance audit from October 2014 to October 2015 

in accordance with generally accepted government auditing standards. 

Those standards require that we plan and perform the audit to obtain 

sufficient, appropriate evidence to provide a reasonable basis for our 

findings and conclusions based on our audit objectives. We believe that 

the evidence obtained provides a reasonable basis for our findings and 

conclusions based on our audit objectives.

8

We asked officials open-ended questions about challenges they experienced in order to 

get their unprompted opinions about the challenges their agencies faced. However, we did 

not ask the officials with each agency if they had experienced a specific challenge. We 

therefore do not know the extent to which all of the selected agencies experienced any 

given challenge. 

Page 5 GAO-16-10 Electronic Monitoring
Numerous agencies at the federal, state, and local levels with varying 

missions monitor or supervise individuals. Criminal justice agency 

missions that require monitoring include pretrial and post-trial services, 

probation and parole services, and immigration enforcement. For pretrial 

services, judicial agencies monitor defendants at the discretion of the 

court for a period of time preceding a scheduled court date. Other criminal 

justice agencies monitor offenders as an alternative to detention. For 

instance, probation agencies typically monitor offenders whom courts 

place on supervision in the community, in lieu of incarceration. The 

Department of Homeland Security’s Immigration and Customs 

Enforcement agency monitors certain aliens prior to adjudication hearings 

or deportation.9 With regard to post-trial monitoring, parole agencies 

monitor offenders who are conditionally released from prison to serve the 

remaining portion of their sentences in the community.

There are many supervisory and monitoring methods, manual and 

electronic, used by criminal justice agencies. See figure 1 for several of 

these methods.

9

For additional information on the Immigration and Customs Enforcement agency’s 

monitoring program, see GAO, Alternatives to Detention: Improved Data Collection and 

Analyses Needed to Better Assess Program Effectiveness, GAO-15-26 (Washington, 

D.C.: Nov. 13, 2014).

Background

Purposes and Methods for 

Offender Monitoring

Page 6 GAO-16-10 Electronic Monitoring
Figure 1: Methods for Supervising and Monitoring Offenders

Manual methods are routinely used to supervise offenders, including 

employment verification, compliance searches, narcotic testing, clinical 

treatment, home or field contact visits, and stakeholder collaboration.10

There are various programs that require close supervision of individuals, 

most predominantly state and local probation or parole agencies’ 

monitoring of selected offender populations (e.g., gang-related and sex 

offenders). Therefore, as a supplement to the traditional manual methods, 

many criminal justice agencies use electronic monitoring technologies. 

Electronic monitoring includes technologies that track individuals’ physical 

location to help supervise compliance with program requirements 

designed to ensure public safety. These technologies are not designed to 

10The supervisory, monitoring method of stakeholder collaboration refers to the sharing of 

GPS printed or recorded data among law enforcement personnel for the purposes of 

investigating incidents, assisting the prosecution, or when responding to a subpoena. 

Page 7 GAO-16-10 Electronic Monitoring
replace manual methods. Rather, they are one tool used in concert with 

other methods for monitoring offenders.

Electronic monitoring technologies include voice verification, radio 

frequency monitoring, and GPS. Voice verification refers to voice 

recognition technology that can verify the identity of an individual. 

Applications include low-risk offenders self-reporting their status by 

telephone. Radio frequency monitoring involves a device that detects a 

signal connected to a home telephone (landline), so that authorities can 

ensure that an offender is at home. However, authorities will not know the 

location of the offender if he/she leaves. GPS is a U.S.-owned utility that 

provides users with positioning, navigation, and timing services. The 

frequency with which GPS data are collected and reported can vary. 

Passive tracking technology collects and stores location and status data, 

which are reported retrospectively. Active tracking technology can 

accomplish near-real-time collection and reporting of location and status 

data.

DOJ’s Office of Justice Programs (OJP) works in partnership with the 

justice community to provide information, training, coordination, and 

strategies for addressing crime-related challenges. NIJ is an office of OJP 

that acts as the research, development, and evaluation agency of DOJ. 

NIJ’s mission is to provide objective and independent knowledge and 

tools to reduce crime and promote justice, particularly at the state and 

local levels. The NIJ Policy, Standards and Grant Management Division 

develops and publishes voluntary consensus equipment standards that 

specifically address the needs of law enforcement, corrections, and other 

criminal justice agencies.

National Institute of 

Justice Standard 

Development

Page 8 GAO-16-10 Electronic Monitoring
Figure 2: Example of an Offender Tracking System Ankle Bracelet

OTS is an electronic monitoring technology consisting of hardware, such 

as an ankle bracelet (see fig. 2), used for collecting and transmitting data 

on an individual’s location, and software for analyzing data collected from 

the hardware device. As written in the current draft, the OTS standard 

pertains to devices using passive tracking or active tracking technology, 

such as GPS. See figure 3 for a graphical depiction of how the 

components of GPS-based OTS interact to collect and transmit location 

data.

Page 9 GAO-16-10 Electronic Monitoring
Figure 3: Global Positioning System (GPS)–Based Offender Tracking System

To develop the OTS standard, NIJ established the Advisory Working 

Group and the Special Technical Committee (STC). The AWG reviews 

the work of the STC and provides high-level guidance on issues that 

affect users, service providers, and manufacturers. It is composed of 

senior-level representatives from selected stakeholder groups and 

individuals experienced in standards development. The STC’s role is to 

identify requirements for OTS technology, consult with leading 

manufacturers, and develop minimum performance requirements and 

associated testing methods for equipment certification. The STC is 

composed of criminal justice practitioners and subject matter and 

technical experts. See figure 4 for NIJ’s organization that supports the

development of the OTS standard.

Page 10 GAO-16-10 Electronic Monitoring
Figure 4: DOJ Organization for OTS Standard Development

a

Conformity assessment(s) are conducted to help ensure that products, materials, services, systems 

or people meet specifications of a relevant standard.

In addition to the OTS minimum performance requirements documented

in the draft standard, the STC has drafted companion documents to 

provide guidance on implementing offender tracking programs and OTS

equipment certification programs. Specifically, the Criminal Justice

Offender Tracking System Selection Application Guide provides guidance

about the functionality, selection, use, and maintenance of OTS.11 The 

Criminal Justice Offender Tracking System Certification Program 

Requirements and the Criminal Justice Offender Tracking System

11See Department of Justice, National Institute of Justice, Criminal Justice Offender 

Tracking System Selection and Application Guide ,NIJ CR-1004.00.00 Draft for Public 

Comment (December 2013).

Page 11 GAO-16-10 Electronic Monitoring
Refurbishment Service Program Requirements addresses accreditation 

requirements for certification bodies.12

There are numerous accredited national and international standard 

development organizations that have published thousands of equipment 

standards in use today. ANSI, which has accredited over 200 standard 

development organizations, requires adherence to a general approach 

displayed in figure 5 when developing American standards.

Figure 5: Standard Development and Maintenance Process

12See Department of Justice, National Institute of Justice, Criminal Justice Offender 

Tracking System Certification Program Requirements, NIJ CR-1004.00 Draft for Public 

Comment (December 2013); and Criminal Justice Offender Tracking System 

Refurbishment Service Program Requirements, NIJ-RP 1004.0 Draft for Public Comments 

(December 2013). 

Standard Development 

Process

Page 12 GAO-16-10 Electronic Monitoring
NIJ collaborated with stakeholders by leveraging expertise from a broad 

variety of criminal justice and technical experts. However, earlier and 

continued collaboration with OTS manufacturers could have better 

informed and facilitated development of the OTS standard. Coordination 

between NIJ and manufacturers has since improved, and manufacturers’ 

major concerns have been addressed.

NIJ’s process for developing the OTS standard is consistent with ANSI 

criteria for accrediting organizations.13 For instance, NIJ sought and 

involved participants from diverse backgrounds with the objective of 

achieving a balance of interests. Participants in the OTS development 

process include criminal justice practitioners from all levels of government 

representing parole, probation, and pretrial services agencies. NIJ also 

made efforts to leverage any national or international standards that 

apply, and solicited and incorporated feedback on the draft standard and 

companion documents through two public comment periods. In particular, 

NIJ formed working groups by appointing members who represent the 

OTS user community, relevant fields of technology, and affected 

professional associations. For example, NIJ created the STC and the 

AWG to inform the development of the OTS standard.

In addition, NIJ efforts extended to collaborating with subject matter 

experts such as ones in the U.S. Air Force and the National Institute of 

Standards and Technology (NIST)—leveraging both organizations’ 

technological backgrounds. For example, the Air Force contributed 

information on GPS for the STC’s consideration so that the STC could 

more fully understand the technology. Similarly, NIST also contributed its 

technical expertise related to its ongoing work with location and tracking 

systems. 

While the standards development process NIJ employed for developing 

the OTS standard is consistent with the process outlined by ANSI, earlier 

and ongoing inclusion of OTS manufacturers could have expedited 

development of the OTS standard. See figure 6 outlining selected events 

throughout the OTS standard development process. The Guide to the 

Project Management Body of Knowledge emphasizes the importance of 

13The ANSI due process requirements for American National Standards, ANSI Essential 

Requirements, is employed by approximately 200 accredited standards development 

organizations, including the U.S. government’s National Institute of Standards and 

Technology.

NIJ Collaborated with 

a Variety of 

Stakeholders, but 

Earlier Manufacturer 

Involvement Could 

Have Expedited 

Development of the 

OTS Standard

Page 13 GAO-16-10 Electronic Monitoring

 
considering stakeholder equities and ensuring their ongoing involvement 

throughout the entire project life cycle. It recognizes that stakeholders’ 

views and interests can be varied, and states that overlooking the views 

of a stakeholder that will be negatively affected can result in an increased 

likelihood of failure, delays, or other negative consequences to a project.

Figure 6: Development Timeline

NIJ’s approach for developing the OTS standard is described by agency 

program officials and STC members as practitioner-driven. Practitioners 

are those who use OTS equipment when tracking the location of 

individuals. Initially, STC practitioners created a list of criminal justice 

needs that they sought to be addressed through OTS technology. 

Subsequent to this assessment of needs and the development of 

corresponding equipment performance requirements, the technical 

experts on the STC were tasked with developing corresponding test 

methods.

In May 2011, approximately 1-1/2 years after the development process 

began, manufacturers, who are to voluntarily ensure their equipment 

conforms to the standard, had a means to formally provide their input. 

Specifically, on May 12, 2011, NIJ held a manufacturer’s workshop to 

seek manufacturer input on the standard. According to manufacturer 

Page 14 GAO-16-10 Electronic Monitoring
representatives with whom we met, manufacturers expressed significant 

concerns related to the feasibility of many requirements and associated 

testing methods in the OTS standard. For example, two manufacturers 

we met with reported that it was unlikely that existing OTS equipment in 

the market could pass performance requirements in the draft standard as 

written, since current technology did not meet the expressed need. This is 

particularly important to the manufacturer community, as the 

manufacturers are the ones that ensure their equipment meets 

requirements in the standard and bear any related costs and market 

consequences if their equipment does not meet the standard. Similarly, 

NIJ had not identified the need for refurbished equipment certification 

program requirements. This is significant, as refurbished equipment is 

routinely provided by OTS manufacturers as part of their service 

agreements with government agencies.

Approximately 1 year after the manufacturers’ workshop, NIJ had not 

provided feedback to manufacturers regarding their concerns. Therefore, 

OTS manufacturers were not aware that NIJ had taken action to 

incorporate their concerns into the draft OTS standard based on their 

review of the draft standard circulated during the first public comment 

period. On July 18, 2012, in a joint letter to NIJ nearing the conclusion of 

the first public comment period, a group of manufacturers wrote the 

following, “The Manufacturers are very concerned that we have received 

absolutely no feedback regarding the information we provided to the 

[Special Technical Committee], and that nothing has been incorporated 

into the standard.”

NIJ officials we met with reported that they considered manufacturer 

input. Specifically, they reviewed manufacturer comments received at the 

2011 workshop as well as those received on the first OTS standard draft 

during the public comment period from June 6 through July 23, 2012. 

However, at the time, NIJ officials told us that they were focused on 

working to address comments from all stakeholders and, therefore, did 

not immediately communicate to manufacturers if or how their comments 

were being addressed.

We reviewed revisions made to the OTS standard since the first draft and 

formal comments submitted in response to both the first and second 

comment periods along with NIJ’s responses, and met with STC 

members and selected manufacturers. According to our review, earlier 

and ongoing involvement of OTS manufacturers in the standard 

development process could have better informed and expedited the OTS 

standard development process. OTS manufacturers could have 

Page 15 GAO-16-10 Electronic Monitoring
contributed to NIJ’s overall understanding of the technology at the 

forefront of the process since they act as both developers and service 

agreement providers to numerous government agencies. For example, 

OTS manufacturers could have better informed and facilitated 

development of the OTS standard by providing insights on OTS 

capabilities and limitations at the outset. Manufacturers could have further 

clarified whether existing OTS technology could meet each performance 

requirement and testing method shortly after being conceived by the STC 

members rather than after the first draft of the OTS standard had been 

developed. For instance, the detection of certain methods used by 

offenders to avoid location monitoring are either not fully developed or 

available to all manufacturers.

While the OTS standard and associated testing methods remain under 

development, coordination between NIJ and manufacturers has improved 

since 2012. For example, through the second public comment period for 

the draft standard, NIJ has communicated to the manufacturers that their 

major concerns related to minimum performance requirements and 

testing methods have been addressed. In addition, according to NIJ 

officials, at the end of the public comment periods, NIJ reached out to 

each manufacturer that provided comments. On the basis of our analysis, 

the current draft OTS standard and changes proposed in response to the 

second public comment period generally reflect input manufacturers have 

provided NIJ. For instance, as a result of stakeholder input, the STC has 

developed refurbishment service program requirements, and it has also 

revised certain performance areas in the draft standard as optional based 

on available technology. NIJ is currently in the final stages of OTS 

standard development and plans to issue the standard by March 2016. As 

NIJ works to finalize the standard, it has invited manufacturers to 

participate in assessing the viability of test methods to be used when 

validating whether an OTS meets requirements set forth in the standard. 

Specifically, it has asked manufacturers to provide samples of their 

equipment. At least one manufacturer we met with is participating in this 

process by providing its OTS equipment for testing, and NIJ reports that 

an additional two manufacturers have as well.

Page 16 GAO-16-10 Electronic Monitoring
NIJ’s draft OTS standard sets minimum performance standards that 

address common operational and circumvention detection needs 

identified by the 9 criminal justice agencies from which we collected 

procurement and policy documents.14 Agencies’ specific performance 

requirements varied and were sometimes more or less rigorous than the 

draft standard, based on factors such as the type of offender supervised 

and environmental conditions in their jurisdictions. Furthermore, these 

agencies did not always define performance requirements corresponding 

to their needs, such as specific location accuracy requirements. By 

setting minimum requirements for a range of commonly identified offender 

tracking system needs, the standard could help agencies more thoroughly 

consider and develop contractual requirements and help ensure their 

needs will be met. Officials from all of the ten agencies we selected stated 

that implementing a standard would be beneficial because, among other 

things, it could provide objective information on performance that could 

inform their procurement processes. Agencies we reviewed, at times, also 

defined additional requirements specific to their circumstances that are 

not in the draft standard, such as a two-way communication feature that 

allows the offender and officer to speak to each other. NIJ officials stated 

the standard is meant to address performance needs that are common to 

a broad range of agencies.

The draft standard addresses common operational and circumvention 

detection needs, such as location accuracy, the ability to obtain an 

offender’s location on demand, programming “zones”—geographical 

areas an offender is or is not to enter— and alerts to report device 

14We met with a total of 10 agencies that had offender tracking programs, but 1 agency 

had not yet finalized its performance requirements. Therefore, information collected from 

this agency was omitted from our performance needs analysis. 

Draft OTS Standard 

and Companion 

Guide Address Many 

Common Needs and 

Challenges Identified 

by Stakeholders

Draft OTS Standard 

Addresses Common 

Needs; Performance 

Requirements Vary by 

Agency

Common Operational and 

Circumvention Detection 

Needs

Page 17 GAO-16-10 Electronic Monitoring

 
tampering, among others. Some of these operational and circumvention 

detection needs are discussed below. See appendix I for additional 

information on specific requirements in the draft standard and summary 

data on the extent to which the requirements met stakeholder needs.

Location accuracy. One of the primary objectives of OTSs is to 

continuously track the location of offenders. NIJ’s draft standard includes 

performance requirements for both indoor and outdoor location accuracy. 

Specifically, it calls for OTS to provide a location that is accurate within 10 

meters 90 percent of the time in an open air environment with no 

obstructions. It also calls for OTS to provide a location that is accurate 

within 30 meters 90 percent of the time when placed in an 8-foot by 8-foot 

single-story structure. The nine agencies we reviewed identified location 

accuracy as important, but none of the agencies had developed a specific 

accuracy requirement. The officials from the agencies we interviewed 

also noted that they must track offenders in a variety of settings, such as 

urban areas with high-rise buildings, which are not accounted for in the 

draft standard. However, the NIJ and STC members responsible for 

developing the standard stated that adding additional types of indoor 

environments would increase the cost of testing. NIJ and manufacturers 

agreed that it is important that the tests not be too costly so that 

manufacturers would voluntarily participate in the standard and consumer 

prices would not be significantly affected, since the cost of testing could 

be passed down to users. Furthermore, as discussed later in this report, 

there are inherent limitations to the GPS technology that prevent it from 

always providing accurate location data in certain conditions, and NIJ’s 

guide provides additional information on addressing these challenges. 

On-demand location. On-demand location allows agencies to determine 

the most recent location of an offender. The draft standard calls for OTSs 

to be able to provide an on-demand location within 3 minutes of a 

request. Five of the nine agencies we reviewed defined an on-demand 

location requirement, with two of the five agencies specifying that they 

require the ability to instantly receive an offender’s location and status. 

Representatives from all three manufacturers with whom we met stated 

that their OTSs cannot provide “instant” location updates because of 

limitations including GPS and cellular technology, and that while quicker 

response times are possible, the 3-minute time frame is a reasonable 

requirement for the minimum performance standard. More specifically, 

these representatives emphasized that the 3-minute time frame is 

appropriate because of the number of steps that must occur to obtain an 

offender’s location. Such steps include, for example, the software calling 

out to the tracking device through a cellular network to acquire data, the 

Testing Conditions

Environmental factors, such as cloud cover, 

could affect the performance of offender 

tracking systems. To help ensure replicable 

and fair testing, the draft standard defines 

specific conditions for testing each 

performance requirement. For example, the 

outdoor location accuracy test is to be 

performed when a minimum cellular speed is 

achieved, there is a clear view of the sky, and 

there is limited cloud cover, among other 

conditions.

Source: GAO summary of National Institute of Justice 

Information. | GAO-16-10

Page 18 GAO-16-10 Electronic Monitoring
device collecting the GPS satellite signals to acquire location data, 

calculating location data, and transmitting the location data back to the 

agency.

Zones. An important feature of OTSs is the ability to develop zones. As 

shown in figure 7, inclusion zones are geographic areas where an 

offender is scheduled to be, such as home or work; exclusion zones are 

geographic areas where the offender is not permitted to visit, such as a

victim’s home, schools, or outside the state or county border. The draft

standard calls for OTSs to configure zones in the shapes of circles,

rectangles, and arbitrarily shaped polygons, as well as be able to have 

zones within zones. Officials from one agency explained, for example,

that it was important that they be able to draw precise exclusion zones

around areas such as schools to prevent the system from alerting when 

the offender is driving by the location. The draft standard also calls for

OTSs to generate zone templates that store a minimum of 50 predefined 

inclusion or exclusion zones, which agencies can apply to any offender.

Officials from one agency explained that zone templates are useful when 

common exclusion zones such as county and state borders or schools

need to be applied to many offenders. The zone shape and zone 

template requirements in the draft standard are more comprehensive than 

any of the requirements established by the nine agencies we reviewed.

For example, eight of the nine agencies we reviewed did not define 

specific zone shape requirements.

Figure 7: Example of Inclusion and Exclusion Zones

Alert notifications. Another important feature of OTSs is to provide 

alerts to notify an agency of a number of different events. These events 

include, among others, occasions when an offender tampers with the 

tracking device by cutting it off or trying to remove it by stretching it over 

his or her foot, an offender violates zone rules by crossing the border of 

an exclusion or inclusion zone, the GPS location is lost; cellular 

Page 19 GAO-16-10 Electronic Monitoring
communication is lost; and when the tracking device battery is low. Alerts 

for tampering with the device and low battery are particularly important 

because cutting the device off and letting the battery die were the most 

common circumvention methods reported by officials at eight of the nine 

agencies we reviewed.15

• Tamper and zone violation alerts: The draft standard calls for the

OTSs to provide alerts within 3 minutes of an ankle strap being cut

and within 4 minutes of ankle strap stretching and zone violations.

The tamper alert requirements in the draft standard are consistent

with the requirements established by five of the nine agencies we

reviewed. Similarly, the zone violation alert requirements are

consistent with the requirements established by four of the nine

agencies we reviewed. The remaining agencies established

requirements for immediate notification of tamper events and zone

violations, though they did not define a time parameter for

“immediate.” Representatives from the three manufacturers we met

with stated that as with the on-demand location feature,

instantaneously sending alert status information is not currently

feasible with their OTSs. Rather, the 3- to 4-minute maximum time

frame in the draft standard for producing an alert was feasible and

would sufficiently test for the OTSs’ ability to provide a near real-time

alert. NIJ officials explained that this time frame was determined by

the practitioners on the STC and balances their performance needs

with the state of the technology.

• Loss of GPS and cellular alerts: The draft standard requires an alert

within 4 minutes of loss of GPS or cellular communication. This time

period was consistent with the requirements established by all of the

agencies we reviewed that had defined such requirements. Officials

from one agency we met with explained that GPS and cellular

communications are lost frequently in their jurisdiction, in areas such

as subways, large office buildings, and basements. Therefore, this

agency required an alert notification after a number of hours without

GPS or cellular communications to avoid overwhelming officers with

alerts. Another agency we met with did not require any alerts for loss

of GPS or communications because it supervised offenders who were

not on probation or parole. In recognition that agencies may wish to

15Officials from the selected agency that had not yet finalized its performance 

requirements also agreed that cutting off the device and letting the battery die were the 

most common circumvention methods. 

Page 20 GAO-16-10 Electronic Monitoring
delay alert notifications in areas where offenders often lose cellular 

communications, the draft standard also calls for OTSs to have the 

ability to alert after communications have been lost for 1 hour. NIJ 

officials explained that STC members included the 1-hour alert 

requirement in the draft standard to reflect a more typical time frame 

used by practitioners. They further stated that agencies could 

continue to request shorter or longer notification requirements from 

their OTS vendors based on their individual needs.

• Low battery alert: The draft standard calls for OTSs to provide a low

battery alert prior to the battery completely discharging, but it does not

specify exactly when this alert is to occur. Eight of the nine agencies

we reviewed required a low battery alert, but the time period for when

they wanted to receive the alert varied. The draft standard also

addresses other battery performance needs, such as battery life. For

more information see appendix I.

Page 21 GAO-16-10 Electronic Monitoring
Optional circumvention requirements. Metallic shielding is the use of 

metallic material to block GPS signals. Jamming is the use of an 

electronic device to block GPS or cellular signals. Both of these 

circumvention methods can prevent agencies from tracking an offender’s 

location. The draft standard includes optional performance requirements 

for the detection of metallic shielding and jamming. According to 

members of the STC, these requirements are optional because only one 

manufacturer offered jamming detection capabilities and had developed 

and patented shielding detection capabilities at the time the standard was 

being drafted. Further, they believe it is important to have a standard with 

performance requirements in which several manufacturers would 

voluntarily participate. According to our review, one of the nine agencies 

required metallic shielding and GPS jamming capabilities as part of its 

procurement process. Officials from eight of the nine agencies reported 

that shielding and jamming were not considered common circumvention 

methods.16 However, officials from one agency explained that jamming 

may be occurring, but they did not have evidence, such as recovered 

jammers or alert data, to support that it is a common occurrence. Officials 

from the nine agencies generally agreed that making shielding and 

jamming detection optional performance requirements is reasonable. 

While one of the nine agencies established a shielding or jamming 

requirement, officials from five of the eight agencies that had not 

established such a requirement stated that these circumvention detection 

capabilities are or could be useful. 

Historical data. OTSs generate a considerable amount of data on each 

offender. The draft standard calls for historical location data, status of all 

alerts, and offender identifiers to be exported into a defined commadelimited text file, a widely used format. All nine agencies we reviewed 

had established a requirement to have access to historical data. Officials 

from these agencies stated that accessing historical data is important 

because the data could be needed as evidence in an investigation, for 

example. In addition to the requirement to make historical data available, 

some agencies also specified particular business practices, such as 

record retention time frames. For example, one agency required that the 

OTS data be retained for 7 years. NIJ’s guide also provides further 

guidance on retaining offender tracking data, including taking into account 

16Officials from the selected agency that had not yet finalized its performance 

requirements also agreed that shielding and jamming were not common circumvention 

methods. 

Jammers

Jammers are electronic devices that can be 

used to prevent offender tracking systems 

from receiving cellular and Global Positioning 

System (GPS) signals. Federal law prohibits 

the operation, marketing, or sale of cellular or 

GPS jammers. The photograph below shows 

an example of a jammer.

Source: GAO analysis of National Institute of Justice 

information; Department of Homeland Security (photograph). 

| GAO-16-10

Page 22 GAO-16-10 Electronic Monitoring
federal, state, and local laws or policies that require certain data be 

maintained for a specific number of years.

Robustness. OTS devices are worn on the body and may be subject to

wear and tear and a number of different environmental conditions,

depending on factors such as where the offender lives and works. The 

draft standard calls for OTSs to function properly after being exposed to 

extreme temperatures ranging from —4 degrees Fahrenheit to 122 

degrees Fahrenheit, immersed in 2 meters of water, undergoing different

shock tests, and exposure to vibration, among other things. One agency

we reviewed had not defined any robustness requirements and none of

the remaining eight agencies had established as many or as specific 

robustness requirements as those in the draft standard. For example,

seven agencies required the OTS device to be shock resistant, but did 

not define what this meant. In addition, none of the agencies had

established vibration exposure requirements. However, four agencies

established robustness requirements that were more rigorous in certain 

areas. For example, one agency required the device to be waterproof up

to 50 feet, while another agency called for the device to function in 

conditions up to 135 degrees Fahrenheit.

In addition to the performance areas identified as part of the draft OTS 

standard, the 9 agencies we reviewed also had a variety of individualized 

needs. These needs were not, however, consistent across agencies. For 

example, 3 agencies required the OTS to have motion detection. Officials 

from 1 agency explained that a no-motion alert could indicate that the 

offender is experiencing a medical emergency or has removed the ankle 

bracelet. In addition, 1 agency required an OTS with two-way 

communication that would allow the offender and officer to speak to each 

other. Officials from this agency said that this has been a useful tool that 

has enhanced offenders’ compliance. One agency also required victim 

support tools such as beepers or cell phones to notify victims of pertinent 

alerts from their offenders’ tracking systems.

Further, agencies had different analytical requirements. For example, 1 

agency required the ability to automate crime scene correlation analysis. 

Crime scene correlation analysis involves comparing offenders’ location 

data against the locations of crimes to identify potential suspects or 

witnesses. Another agency required analysis tools to identify common 

places at which each offender spends time. Officials from this agency 

explained that they use the analysis to help find offenders in the event 

that they abscond.

Individualized Needs Not 

Considered Minimum 

Performance Requirements in 

the Draft Standard

Page 23 GAO-16-10 Electronic Monitoring
NIJ and STC members stated that the standard is meant to establish 

minimum performance requirements that would be common to a broad 

range of criminal justice uses. Further, they stated that agencies could 

continue to specify additional requirements beyond those in the standard 

as part of their individual procurement processes. In addition, the 

technical experts on the STC with whom we met stated that as OTS 

technology advances, the common needs of agencies may also change. 

It would, therefore, be important to periodically reassess the minimum 

performance requirements in the standard to determine if they are still 

valid or if they should be changed to address changes in practitioners’ 

needs or advances in technology. This is consistent with NIJ’s standard 

development process, which calls for standards to be reevaluated every 3 

to 5 years.

Officials from the 10 criminal justice agencies we met with also identified 

programmatic challenges with implementing offender tracking programs, 

such as managing public expectations of what the technology can 

achieve, as well as technical limitations that could affect the success of 

their offender tracking programs.17 NIJ’s draft guide provides information 

and guidance on these challenges and other considerations. In 

recognition of the range of agencies, environments, resources, and 

objectives of offender tracking, the draft guide does not offer “one size fits 

all” solutions.

Challenges commonly cited by officials from the 10 agencies we met with 

included public expectations, establishing response protocols, and 

managing workloads. The draft guide discusses these and other 

programmatic considerations that can affect the success of an electronic 

monitoring program.

Public expectations. One of the challenges officials cited was 

misconceptions among the public about how offender tracking programs 

operate. According to officials, common misconceptions include the 

beliefs that (1) officers are stationed at computers and watch the live 

17We included information on challenges provided by officials from all 10 criminal justice 

agencies we met with that had OTS programs. We asked officials open-ended questions 

to get their unprompted opinions about challenges their agencies had experienced. 

However, we did not ask the officials with each agency if they had experienced a specific 

challenge. Therefore, we were able to identify different challenges agencies faced, but not 

the extent to which all of the selected agencies had experienced any given challenge. 

The OTS Standard’s Draft 

Companion Guide 

Addresses Potential 

Challenges and Other 

Considerations

Programmatic Challenges

Page 24 GAO-16-10 Electronic Monitoring
movement of offenders 24 hours a day, 7 days a week, and (2) offender 

tracking technology allows officers to prevent bad behavior before it 

happens.

Agency officials reported that officers are rarely stationed at computers 

watching the live movement of offenders. Instead, as one of many 

supervisory and monitoring methods, practitioners commonly rely on OTS 

devices collecting location information and developing alerts that notify 

them when offenders may be violating restrictions imposed upon them. 

While OTS devices do collect data on offenders’ location, the information 

is not sufficient for officers to make definitive conclusions regarding 

offenders’ behavior. As officials from 1 agency noted, offenders can 

commit crimes without setting off any alerts. In addition, some offenders 

may purposely keep the device on to prevent alerting authorities prior to 

or while they commit a crime. Furthermore, even if an offender sets off an 

alert, an agency may not respond immediately. Response time depends 

on the alert protocols established by the agency and factors such as 

staffing and resources, as discussed later in this report. Although OTSs 

may not deter or prevent all offenders from recidivating, officials from 1 

agency emphasized the important role GPS location data can play in 

providing evidence to solve crimes.

Understanding key aspects of how offender tracking programs operate is 

particularly important for victims. Representatives from the victims’ rights 

organizations we met with explained that victims should understand the 

limitations of the technology so they do not develop a false sense of 

security. The draft guide contains a section on managing media relations 

to inform the public of the agency’s mission, policies, and practices. It 

advises agencies to provide proactive updates on the program and have 

a plan to communicate to the media in the event that a critical incident 

occurs.

Response protocols. Officials from the agencies we met with told us that 

it was challenging to develop appropriate response protocols that balance 

the likelihood of risk to public safety with available resources. Officials 

reported that alerts for loss of GPS, cellular communications, and low 

battery can occur frequently, even when the offender has no intention of 

circumventing tracking. Responding to all such alerts can overwhelm 

officers, according to officials with whom we met. To help reduce officers’ 

alert workload, 1 agency we met with set up its OTS to generate an 

exclusion zone alert only after multiple consecutive location points were 

collected within an exclusion zone. The officials explained that this 

reduced the number of alerts caused by inaccurate location data and 

Investigating Crimes

Global Positioning System (GPS) data from 

offender tracking systems (OTS) can be used 

to help investigate and solve crimes. For 

example,

• Officials from 1 agency we met with

reported that two sex offenders were

identified as suspects in the killing of four

women in California based upon the GPS

data collected from the OTS, which

placed them at the crime scenes.

• OTS data can also help eliminate

offenders as suspects. In Florida, the

mother of an abducted boy pointed to a

sex offender who lived in the vicinity as a

suspect. The GPS data collected by the

OTS showed that the offender had not

been at the boy’s location and helped law

enforcement exclude the offender as a

suspect.

Source: GAO analysis of criminal justice agency information. | 

GAO-16-10

Page 25 GAO-16-10 Electronic Monitoring
situations where the offender was driving by an exclusion zone. On the 

other hand, reducing the number of alerts officers receive may increase 

the risk that an offender will be able to circumvent tracking or commit a 

new crime. One victims’ rights group representative noted that an agency 

can have the best OTS technology available, but it will not help protect 

the public if the agency does not use or respond to the data it generates.

Critical incidents in which offenders with a GPS tracking device have 

committed serious crimes, including rape and murder, have caused some 

agencies to reassess how they respond to alerts and oversee their 

programs. For example, officials from 1 agency’s regional office decided 

to receive tamper alert notifications only after the device had been in a 

tamper status for 5 minutes. The 5-minute time period was chosen to help 

prevent alerts not indicative of a violation, such as frequent impact to the 

device as a result of the offender’s work environment. However, this 

delayed notification was inconsistent with the agency’s national policy and 

resulted in one offender being able to generate a series of tamper alerts 

over several weeks that lasted less than 5 minutes. In this case, an officer 

did not receive alert notifications and did not investigate the matter.18 This 

offender subsequently pleaded guilty to raping a child and killing the 

child’s mother after removing his tracking device. Following this incident, 

the agency’s national office investigated the supervision of the offender 

and reaffirmed the importance of receiving immediate notifications for and 

responding to all tamper alerts.

In recognition of the importance of establishing appropriate response 

protocols, the draft guide includes examples for an inclusion zone 

violation and a low battery alert. The draft guide also highlights a number 

of factors that agencies should take into consideration when determining 

how to respond to alerts. For example, the draft guide advises agencies 

to consider the offender’s conviction type, level of risk, and whether there 

are victims who should be notified. The draft guide also advises agencies 

to consider their available resources when determining who will be 

notified of alerts and when. Specifically, agencies should determine if they 

are able to respond to alerts 24 hours a day, 7 days a week, and whether 

they can use a vendor to monitor or respond to alerts prior to agency staff 

18The tamper events were also recorded on the vendor’s website and were to be reviewed 

daily in accordance with the agency’s national policy. However, the agency’s regional 

office did not review the tamper event records and were thus unaware of the alerts

attributable to the offender. 

Page 26 GAO-16-10 Electronic Monitoring
being notified. Figure 8 shows examples of two alert response 

approaches—one in which all alerts are received by an officer and one in 

which a monitoring center reviews alerts to determine whether an officer

should be notified.

Figure 8: Examples of Different Alert Response Models

Workload. Implementing an OTS program can create workload 

challenges. For example, officials we met with said that they have 

experienced high or unpredictable officer caseloads and the need for 

overtime to respond to alerts 24 hours a day, 7 days a week. The draft 

guide asserts that OTS programs need to have sufficient staffing to meet 

the increased workload demands. It also states that failing to adequately 

staff an OTS program can lead to officer burnout, unanticipated overtime 

expenses, high turnover rates, and protests from collective bargaining 

Page 27 GAO-16-10 Electronic Monitoring
groups. The draft guide provides information on the multiple new duties 

that OTS programs may require and that agencies should consider when 

making decisions about the size and objectives of their program. These 

duties may include, for example, offender orientation to instruct the 

offender of program rules and conditions, installation of offender tracking 

equipment, routine inspection of offender tracking equipment to ensure 

the offender has not tampered with it, responding to alerts, and reviewing 

location tracking data.

The draft guide also provides information on different approaches and 

considerations for addressing workload issues. For example, if there is a 

large enough offender population, the draft guide states that a specialized 

workforce for offender tracking could result in efficiencies. Hours of 

operation are another consideration. According to the draft guide, 

agencies should determine whether OTS alerts should be responded to 

24 hours a day, 7 days a week, or if passive tracking is a viable 

alternative part or all of the time. Data review requirements can also affect 

officers’ workloads. Reviewing all offender tracking data takes a 

significant amount of time, but can help officers identify patterns and 

deviations that warrant further investigation. Thus, the draft guide states 

that agencies should determine whether a review of all offender tracking 

data is needed or if responding to alerts is sufficient to achieve program 

goals. Further, agencies can contract with vendors to provide various 

levels of services including training, installing and inspecting equipment, 

responding to certain alerts, dispatching alerts to criminal justice officers, 

and data analysis. The draft guide advises agencies to take into account 

both program objectives as well as stakeholder expectations when 

determining what approach to take.

Other considerations. In addition to addressing the challenges raised 

by officials from the agencies with whom we met, the draft guide also 

discusses a number of other issues agencies should consider when 

implementing an offender tracking program. For example, the draft guide 

provides information on common procurement processes and what to 

look for in a vendor. It also addresses training issues and provides 

information on establishing contractual requirements for the vendor to 

provide training, as well as considerations for training content, format, and 

frequency. Furthermore, the draft guide discusses several OTS data 

considerations, including managing data that are evidence related to a 

crime and data retention issues, such as the data format, how long the 

data will be kept, and who will have access to the data. Another 

consideration is measuring offender tracking program outcomes. The 

draft guide advises that the appropriate approach to measuring success 

Page 28 GAO-16-10 Electronic Monitoring
will be determined by the objectives of the program, which can range from 

reducing overcrowding in correctional institutions to enhancing public 

safety.

Cellular and GPS reception can affect the OTSs’ location accuracy or 

ability to report location and alerts. Officials from the 10 agencies with 

whom we met all experienced challenges with cellular and GPS signal 

reception in certain areas of their jurisdictions. The draft guide provides 

information and guidance for how to mitigate these challenges.

Cellular coverage. OTSs rely on cellular communications to transmit 

location data; thus an agency will not be able to determine an offender’s 

location in near real time while he or she is in an area with insufficient 

cellular coverage. Officials from all 10 criminal justice agencies stated that 

there are areas in their jurisdictions that lack sufficient cellular coverage 

to allow devices to perform as designed. The draft guide suggests that 

agencies inquire about the cellular providers that vendors use for their 

equipment and test the devices prior to making a final procurement 

decision. If cellular coverage is limited, the draft guide states that one 

option is to use passive tracking, where the location and alert status data 

are transmitted to the agency through a landline at a predetermined 

interval, usually once a day. 

GPS signal reception. Signals from a minimum of three GPS satellites 

are required to calculate location, and the greater number of satellite 

signals received, the more accurate the location will be. As with cellular 

coverage, officials from all 10 criminal justice agencies we met with stated 

that there are areas in their jurisdictions where their OTSs lose or have 

compromised GPS signal reception. The draft guide provides information 

on factors that can affect GPS signal reception and cause inaccurate 

location data—often referred to as GPS drift—to help agencies 

understand the limitations of OTSs. Specifically, the draft guide notes that 

structures, foliage, cloud cover, and natural land formations such as 

canyons can block GPS signals. In addition, buildings or bodies of water 

can create a phenomenon known as multi-path, where the GPS signal is 

reflected off one or more surfaces prior to reaching the tracking device. 

Because GPS calculations usually assume that a signal follows a straight 

line to the tracking device, multipath reflections can significantly affect the 

accuracy of the location data.

The draft guide also provides information on OTS features that can help 

mitigate GPS signal reception issues that agencies can consider and test 

when making equipment selection decisions. For example, OTS with 

Technical Limitations

Suggested Field Tests

The draft companion guide suggests agencies 

test offender tracking systems (OTS) prior to 

making a selection decision to evaluate how 

they perform in their jurisdictions. Since local 

factors, such as cellular coverage and the 

environment, can affect OTSs’ ability to 

accurately track an offender’s location or 

transmit location data, the draft guide advises 

agencies to test OTSs in the following areas:

• urban areas with high-rise structures,

• wooded areas,

• residential settings, and

• inside a large building or shopping mall

Source: GAO summary of National Institute of Justice 

information. | GAO-16-10

Page 29 GAO-16-10 Electronic Monitoring
antennas that can track more satellite signals will be less subject to drift 

and will have greater location accuracy. Table 1 provides further 

information on different OTS features discussed in the draft guide that 

can help mitigate GPS signal reception issues.

Table 1: Offender Tracking System (OTS) Features to Mitigate Global Positioning System (GPS) Signal Reception Issues

Feature Description

Antenna A well-placed antenna that receives more location signals can enhance location 

accuracy.

Assisted GPS Some OTSs use assisted GPS to help enhance location accuracy. Assisted GPS uses 

strategically positioned ground stations with GPS antennas. Because the exact locations 

of the ground stations are known, the system will be able to determine exactly how 

accurate the GPS-derived location calculation is at those stations, and then take this 

information into account when calculating the location of nearby GPS tracking devices.

Advanced Forward Link Trilateration Advanced Forward Link Trilateration uses cellular signals, which are stronger than GPS 

signals, from a minimum of three cellular towers to calculate a location. This is usually a 

secondary location methodology used when GPS signals are not available. In areas 

served with numerous cell towers, this methodology is generally accurate within 50 

meters.

Beacons Beacons are auxiliary devices that can be used in conjunction with OTSs to help with 

indoor tracking. Beacons are generally installed at a participant’s home or workplace and 

can enhance location tracking in areas with poor GPS reception, as well as conserve 

battery power. They use radio frequency communications to determine if the offender 

tracking device is within range. If the offender tracking device is within range, the beacon 

can turn off the GPS on the tracking device, and instead the beacon will communicate to 

the agency that the offender is within range of the beacon. 

Precision algorithms Some OTSs have precision algorithms that take into account an offender’s previous 

location and use statistical probabilities to produce an estimated location that tends to be 

more accurate than locations based on raw GPS data.

Source: GAO analysis of National Institute of Justice Information. | GAO 16-10

We provided a draft of this report to DOJ, DHS, and AOUSC for their 

review and comment. None of the agencies provided written comments. 

DHS and AOUSC provided technical comments, which we incorporated 

as appropriate. 

As agreed with your office, unless you publicly announce the contents of 

this report earlier, we plan no further distribution until 30 days from the 

report date. At that time, we will send copies to the appropriate 

congressional committees, the Attorney General, the Director of the 

Administrative Office of the U.S. Courts, the Secretary of the Department 

of Commerce, the Secretary of the Department of Homeland Security, 

and other interested parties. In addition, the report is available at no 

charge on the GAO website at http://www.gao.gov. 

Agency Comments 

and Our Evaluation

Page 30 GAO-16-10 Electronic Monitoring
If you or your staff have any questions about this report, please contact 

me at (202) 512-8777 or maurerd@gao.gov. Contact points for our 

Offices of Congressional Relations and Public Affairs may be found on 

the last page of this report. GAO staff who made key contributions to this 

report are listed in appendix II.

Sincerely yours,

David C. Maurer

Director

Homeland Security and Justice Issues

Page 31 GAO-16-10 Electronic Monitoring
Appendix I: Operational and Circumvention 

Detection Needs Addressed in NIJ’s Draft 

Offender Tracking Standard

The National Institute of Justice’s (NIJ) draft standard addresses common 

operational and circumvention detection needs. Table 2 summarizes 

some of the operational and circumvention requirements in the draft 

standard. The agencies’ requirements were sometimes more or less 

rigorous than those in the standard.1 Furthermore, in some instances, 

agencies did not define a performance requirement for a specific 

operational or circumvention detection need.

Table 2: Comparison of Selected Operational and Circumvention Detection Needs to Draft Offender Tracking System 

Standard Minimum Performance Requirements

Need

Summary of draft standard minimum performance 

requirement

Draft standard versus selected 

agencies’ requirements

Location accuracy The offender tracking system (OTS) shall provide a 

location that is accurate:

• within 10 meters, 90 percent of the time in an open 

air environment with no obstructions, and

• within 30 meters 90 percent of the time when placed 

in a 8-foot by 8-foot single-story structure. 

Agencies that did not define a 

requirement: 9 agencies

Data collection rate The OTS shall have an adjustable data collection rate 

that ranges from at least one location point per minute to 

one location point every 15 minutes.

Standard is as rigorous: 6 agencies

Standard is not as rigorous: 2 agencies

Agencies that did not define a 

requirement: 1 agency

Data upload rate The OTS shall have the capability to upload data points 

at a minimum of once every 15 minutes.

Standard is as rigorous: 4 agencies

Standard is not as rigorous: 1 agency

Agencies that did not define a 

requirement: 4 agencies

On-demand location The OTS shall be able to provide an on-demand location 

and status update within 3 minutes of the request.

Standard is as rigorous: 2 agencies

Unclear: 2 agenciesa

Standard is not as rigorous: 1 agency

Agencies that did not define a 

requirement: 4 agencies

Battery charging The OTS shall complete the charging process, from a 

discharged state, within 2 hours for a one-piece system 

or within 4 hours for a multipiece system, and hold a 

charge for the remainder of the day.

Standard is as rigorous: 4 agencies

Standard is not as rigorous: 1 agencyb

Agencies that did not define a 

requirement:4 agencies

1

We met with a total of 10 agencies that had offender tracking programs, but 1 agency 

had not yet finalized its performance requirements. Therefore, information collected from 

this agency was omitted from our performance needs analysis. 

Appendix I: Operational and Circumvention 

Detection Needs Addressed in NIJ’s Draft 

Offender Tracking Standard

Page 32 GAO-16-10 Electronic Monitoring

 
Appendix I: Operational and Circumvention 

Detection Needs Addressed in NIJ’s Draft 

Offender Tracking Standard

Need

Summary of draft standard minimum performance 

requirement

Draft standard versus selected 

agencies’ requirements

Battery life expectancy Batteries shall be capable of 365 cycles of charging and 

discharging.c Standard is as rigorous: 6 agencies

Agencies that did not define a 

requirement: 3 agencies

Tamper alert The OTS strap shall generate a time-stamped tamper 

event after no longer than 5 seconds of being cut and 

provide an alert within 3 minutes of the time stamp.

On application of an “inside out” force sufficient to cause 

the strap to either separate from the body-attached 

device or stretch in excess of 5 percent, an alert shall be 

generated and received within 4 minutes. 

Standard is as rigorous: 5 agencies

Unclear: 4 agenciesd

Zone violation alert The OTS shall generate a “zone violation” alert within 4 

minutes of crossing the boundary of an exclusion zone 

(an area the offender is not to be in, such as a victim’s 

home) or an inclusion zone (an area the offender is to be 

in, such as work or home). 

Standard is as rigorous: 4 agencies

Unclear: 5 agenciese

Loss of location alert The OTS shall demonstrate detection and alerting for 

loss of location (e.g., loss of GPS) incidents within 4 

minutes.

Standard is as rigorous: 6 agencies

Unclear: 1 agencyf

Agencies that did not define a 

requirement: 2 agencies

Loss of communications alert The OTS shall demonstrate detection and alerting for 

incidents in which communications (e.g., cellular 

communication) have been lost for a period of at least 1 

hour. Further, the OTS shall be capable of providing an 

alert within 4 minutes when communications have been 

lost.

Standard is as rigorous: 7 agencies

Unclear: 1 agencyg

Agencies that did not define a 

requirement: 1 agency

Source: GAO analysis of National Institute of Justice (NIJ) and selected criminal justice agency information. | GAO 16-10

a

Two agencies required an immediate on-demand location feature, but did not define a time 

parameter for immediate. As discussed in this report, the current technology from the manufacturers 

we met with does not allow for instantaneous on-demand location requests.

b

One agency required the OTS to charge within an hour. However, the manufacturer that was 

awarded this agency’s contract stated that while 1 hour would fully charge its OTS’s battery during 

regular daily use, it could take up to 2 hours to charge if the battery was completely discharged, as 

required in the standard.

c

For purposes of comparison, we assumed the OTS would be subject to one charging cycle per day.

d

Four agencies required immediate tamper alert notifications, but did not define a time parameter for 

immediate. As discussed in this report, the current technology from the manufacturers we met with 

does not allow for instantaneous alerts.

e

Five agencies required immediate zone violation alert notifications, but did not define a time 

parameter for immediate. As discussed in this report, the current technology from the manufacturers 

we met with does not allow for instantaneous alerts.

f

One agency required the OTS to be able to detect and alert when there was both a loss of Global 

Positioning System (GPS) and motion was detected, rather than just a loss of GPS alone. Agency 

officials explained that this combination alert could be indicative of an offender purposefully trying to 

block GPS while he or she moved around.

g

One agency required the OTS to alert when a scheduled data upload was missed because of a loss 

of communications, rather than when cellular communications had been lost for a certain amount of 

time.

Page 33 GAO-16-10 Electronic Monitoring
Appendix II: GAO Contact and Staff 

Acknowledgments

David C. Maurer, (202) 512-8777 or maurerd@gao.gov. 

In addition to the contact named above, Joseph P. Cruz (Assistant 

Director), Pamela Aker, David Alexander, Willie Commons III, Susan 

Czachor, Dominick Dale, Eric Hauswirth, Heather May, Linda Miller, and 

Michael Tropauer made key contributions to this report.

Appendix II: GAO Contact and Staff 

Acknowledgments

GAO Contact

Staff 

Acknowledgments

(441254) Page 34 GAO-16-10 Electronic Monitoring
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