U.S. flag

An official website of the United States government, Department of Justice.

Understanding Domestic Radicalization and Terrorism

A National Issue Within a Global Context
National Institute of Justice Journal
Date Published
August 14, 2020
Globe with focus on the United States showing state outlines
m.elyoussoufi/iStock.com (see reuse policy).

In 2017, there were 10,900 terrorist attacks around the world that killed more than 26,400 people, according to the National Consortium for the Study of Terrorism and Responses to Terrorism (START).[1] The number of terrorist attacks per year in the United States in the post-September 11 era has increased from 33 in 2002 to 65 in 2017.[2] It is evident that the number of terrorist attacks and the lethality of these attacks are increasing at alarming levels within the United States and abroad, and terrorism is a pressing national issue that lies very much within a global context.

With the threat of terrorism on the rise and acts of terrorism occurring increasingly at a national and global level, it is imperative — perhaps now more than ever — that we ensure our resources are being directed to the most practical and evidence-based means of countering violent extremism. Understanding why and how people radicalize, as well as what can be done to prevent radicalization or intervene during the process, are key to countering violent extremism.

See “Defining Terrorism”

What makes this issue complex is that in the United States, terrorist acts are carried out by people who are motivated by a wide variety of ideological viewpoints, who have gone through different radicalization processes, and who have unique grievances or life experiences that lead them toward radicalization to terrorism. This, in turn, makes it difficult to target prevention and intervention efforts toward any one “vulnerable” population. Radicalization to terrorism can be motivated by extremist groups/ideologies, or it can occur at an individual level (commonly referred to as “lone wolf terrorism”). In the United States, terrorists are usually associated with one of the six most commonly known ideologies: right-wing extremism, left-wing extremism, environmental extremism, nationalist/separatist extremism, religious extremism, and single-issue extremism.[3] Further, the nature of radicalization and types of extremist attacks are dynamic, changing from year to year and from decade to decade.[4]

NIJ plays a vital role in funding research related to domestic radicalization and terrorism in the United States. As a federal leader in the field, NIJ’s work is complementary to that of the Department of Homeland Security (DHS) and Department of Defense, as well as international partners in Canada, the United Kingdom, Australia, and New Zealand, among others. Although the field of domestic radicalization and terrorism research as a whole is considered to be in its infancy (compared to other fields in criminology, such as gangs or violent crime), significant achievements have been made.

NIJ’s Terrorism and Radicalization Research

In response to the September 11 terrorist attacks, NIJ started working with the National Academies in 2002 to help craft a research agenda to move the field of terrorism research forward. NIJ funded projects that focused on:

  • Developing terrorism databases for analysis.
  • Improving the criminal justice response.
  • Addressing potential high-risk terrorism targets.
  • Examining the links between terrorism and other crimes.
  • Studying the organization, structure, and culture of terrorism.

After investing in numerous projects, NIJ played a shared role in the development and longevity of numerous national and global terrorism databases (such as the American Terrorism Study and the Global Terrorism Database) and institutions (such as START at the University of Maryland, the Terrorism Research Center at the University of Arkansas, and the Triangle Center on Terrorism and Homeland Security at Duke University).

In its fiscal year 2012 appropriation, Congress directed NIJ to administer dedicated funding for “research targeted toward developing a better understanding of the domestic radicalization phenomenon, and advancing evidence-based strategies for effective intervention and prevention.”[5] Every year since then, NIJ has received similarly dedicated funding to carry out this mission. In its first five years, the goal of NIJ’s Domestic Radicalization and Terrorism research portfolio was to answer the following questions:

  • What are the primary drivers of radicalization to violent extremism, and how do they vary across cohorts (e.g., by grievance, by age, by socioeconomic categories)?
  • How is radicalization to violent extremism analogous to other forms of extreme violence, such as mass casualty events and gangs?
  • Which policy choices or programmatic interventions prevent or reduce radicalization to violent extremism, induce disengagement from violent extremism, or support deradicalization and desistance from violent extremism?

The program aimed to answer these questions for the benefit of multiple stakeholders but considered criminal justice agencies and their community partners as the primary beneficiaries.

Between 2012 and 2019, NIJ made competitive awards for 34 projects through its annual domestic radicalization and terrorism solicitation. Three of the most common topic areas funded under these awards involve research surrounding:

  • The drivers of radicalization.
  • The role of the internet and social media in the radicalization and recruitment process.
  • Program evaluations of extremism prevention and intervention programs.

Some of the most important findings to date come from a set of NIJ-commissioned papers that summarize key findings from approximately 15 NIJ-funded studies and an international conference.[6] For example, one paper explores research on risk factors associated with radicalization to violent extremism that was presented at an international conference in 2015. These risk factors include violent extremists in an individual’s social network, identity processes, violent extremist belief systems and narratives, group dynamics, connections with violent extremists and violent extremist material through the internet and social media, and grievances.[7]

Two papers on radicalization risk factors[8] and the radicalization process[9] emphasize the social nature of radicalization. Reasons for concern may include an individual’s associates and drastic changes in those relationships. The papers also found 16 potential risk factors associated with attempts to engage in terrorism by both group-based and lone-actor terrorists. Although lone actors tend to be more public with their grievances and their intent to do harm,[10] they share these common risk factors with group-based terrorists:

  • Having a criminal history.
  • Having mental health issues (or receiving a diagnosis of schizophrenia or delusional disorder).
  • Being unemployed.
  • Being single.
  • Being a loner (or socially isolated).
  • Having military experience.

Meanwhile, NIJ-funded researchers at Georgia State University compared the motive, weapon use, and behaviors of three types of terrorists — lone-actor terrorists (not related to or in contact with a terrorist group), solo terrorists (those who act alone but are related to a terror group or network), and mass murderers. They found that these individuals can be distinguished by the degree to which they interact with co-conspirators, their antecedent event behaviors, and whether (and the degree to which) they leak information prior to an attack.[11] NIJ has funded other comparative studies of extremists and gang members, as well as extremists and human traffickers, among others.[12]

NIJ has also funded program evaluations, most notably an evaluation of the first Muslim-led, community-based countering violent extremism (CVE) program.[13] Researchers at the University of Massachusetts Lowell found that peers were the most likely to notice early signs of radicalization, but they had a reduced likelihood of reporting due to a reluctance bias. The research team developed a metric tool called a “suite of measures” that pertains to various types of psychological processes, motivations, states, and social circumstances; the tool can be readily adapted to CVE program evaluations.

Although many of the questions NIJ originally sought to answer have been addressed to some degree, many uncertainties remain. For example, we have learned about many of the drivers of radicalization and the similarities and differences between terrorism and other forms of violent crime. We have also learned that a majority of recruitment and radicalization occurs via the internet and social media. However, one of the most important findings may be that there is no one-size-fits-all approach to these questions. There is no single checklist that determines whether someone is on the path to becoming a terrorist. Additionally, although there have been many takeaways from NIJ-funded evaluations of intervention and prevention programs, the implementation, replication, and evaluation of such programs are still lacking in this field.

Advancing Knowledge

Forthcoming awards and publications in NIJ’s portfolio will help further advance the field of terrorism and radicalization studies. NIJ-funded researchers at the University of Virginia are studying women who have been involved with violent extremism to identify strategies used by the Islamic State group to recruit and radicalize Western women.[14] Another project is using post-September 11 era geocoded, terrorism-related precursor data to identify where people radicalize versus where terrorist events actually take place.[15] This is especially important as some of NIJ’s previously funded research has found that approximately 60% of terrorists lived more than 30 miles away from their terrorist target.[16]

NIJ-funded researchers at the RAND Corporation are conducting interviews with the families and close friends of individuals who have radicalized.[17] These interviews will offer unique insights and perspectives from the people who were closest to the radicalized individual because they are the ones most likely to detect changes in behavior.

A recent NIJ grant will build on landmark studies from Australia and the United Kingdom to understand the dynamics of and barriers to community reporting in the United States.[18] NIJ hopes that the study resulting from this grant will bridge a large research gap by attempting to understand the triggers, thresholds, facilitators, and barriers to reporting terrorism involvement. Further, the results could potentially inform the broader issue of reporting about violence in general, as the study will compare perspectives about reporting involvement in terrorism versus involvement in nonterrorist mass violence. The potential impact on the field is expected to be high, as it would be the first study of its kind to allow for direct comparison of sentiments and issues surrounding reporting by family and close friends in the United States, the United Kingdom, and Australia.

Lastly, in 2017, NIJ began a new publication series called Notes From the Field.[19] This series serves as a platform for leading criminal justice practitioners to share promising practices and lessons learned on pressing issues. It is part of an effort by NIJ to better connect with and learn from law enforcement. Notes From the Field recently launched a series on terrorism prevention to help fill gaps in knowledge and remain on the forefront of the most cutting-edge research in the field.

NIJ’s Role at the Federal and International Levels

NIJ also plays a large role in advancing radicalization and terrorism research at the federal and international levels. The Institute is one of the leading federal agencies that fund research on this topic.

Through meetings, project collaborations, and working groups, NIJ has established successful working relationships with its national and international partners. For example, NIJ has coordinated with DHS and other federal partners through the Countering Violent Extremism Task Force. As a member of the Task Force’s Research and Analysis Working Group, NIJ shares research findings with the group and stays abreast of research priorities, gaps, and progress made across entities within the federal government. NIJ also organizes expert panels at conferences, such as the annual meetings of the International Association of Chiefs of Police and the American Society of Criminology, which helps to translate research findings directly into law enforcement practice and target and enhance future research efforts.

On an international level, NIJ is involved with the Five Country Research and Development (5RD) Network, which includes government agency representatives from Australia, Canada, New Zealand, the United Kingdom, and the United States. The group works to cooperate, collaborate, and exchange information to ensure efficiency and coordination of applied research and development work relevant to a variety of domestic security topics. The DHS Science and Technology research team leads the group, which first met in 2015 to discuss best practices and lessons learned from international partners in efforts to counter violent extremism. The 5RD participants communicate regularly to share information and coordinate efforts to develop new technologies to prevent crime, ensure security, and protect citizens.

The 5RD Network has commissioned systematic reviews of research and evaluation efforts from all five countries to build a “global evidence-base for terrorism prevention, policy, strategy, and activity.”[20] These systematic reviews will cover subtopics such as common factors leading to radicalization, online indicators of radicalization, the role of the media in the radicalization process, and how community support and societal connections influence the prevention of radicalization. Recognizing that the threat of terrorism transcends all borders and ideologies, NIJ is hopeful that the rigorous and high-quality scientific findings from these reviews will help guide policymakers and practitioners in their decision-making.

Looking Forward

NIJ’s focus for the future will be to continue funding rigorous evaluations, developing stronger baseline knowledge of radicalization processes, and informing policy and programming through research to better understand how and why people radicalize, and which programs and policies work best to prevent radicalization from occurring.

Further, NIJ hopes to address significant research gaps in the field, such as gaps in understanding disengagement and deradicalization processes and what programs can be developed and delivered to those incarcerated for terrorist offenses. While it is vital to understand the “push” (forcing) and “pull” (attracting) factors behind why individuals become terrorists to help inform prevention and intervention policies and programs, it is equally important to understand these factors to inform disengagement and deradicalization efforts. If we do not understand what makes terrorism attractive to certain individuals and how terrorism is unique from other forms of violence, we will not be able to prevent, intervene with, deradicalize, or reintegrate those susceptible to this phenomenon. Bridging this gap would not only complement NIJ’s previous investments, it would lead to future opportunities for rigorous comparative research initiatives in conjunction with other topics, such as mass shootings and gangs.

By understanding disengagement and deradicalization, NIJ hopes to inform policy and practice around programming for those convicted of terrorist offenses in confinement as well as post-release. In the United States, it is estimated that 275 individuals have been convicted of terrorism-related charges since the September 11 terrorist attacks.[21] Although some of these individuals are serving life sentences, many others are expected to be released. For example, as of December 1, 2018, 168 individuals have been charged with offenses related to the Islamic State group alone (not including those motivated by any other type of terrorist ideologies); their average sentence is 13.2 years.[22] A majority of these individuals will be released, often sooner than we would expect. Hundreds of others are incarcerated for terrorism offenses or terrorism-related charges across the country, and there is still much to be learned about how these individuals should be reintegrated back into society, what the recidivism rate for these people will be, and to what extent their ideologies have changed after incarceration. Questions about the effectiveness of prison programming, access to services, and success with reintegration remain. Those who commit terrorist offenses are a relatively new and niche population that has been under-studied; immediate research and programming attention are needed to keep up with the growing number of individuals being released on such charges. This is a widely recognized concern in the field of terrorism research, and NIJ hopes to play a key role in fulfilling this urgent research need.

Overall, NIJ funding has allowed for valuable contributions to the field of domestic radicalization and terrorism research. However, there are still many uncertainties around how to intervene before an individual radicalizes or mobilizes to violence. NIJ intends to remain engaged in combating the constantly evolving threats presented by violent extremism through soliciting rigorous research, engaging with stakeholders, and informing policymakers.

For More Information

Learn more about NIJ’s domestic radicalization and terrorism portfolio.

About This Article

This article was published in the NIJ Journal Issue Number 282.

This article discusses the following grants:

Sidebar: Defining Terrorism

The definition of terrorism/terrorists is often a contested issue, with academics, government entities, media outlets, and others using varying language to define this concept. For the purposes of soliciting applications for research, NIJ has defined terrorists as “those individuals who commit or provide support for the commission of ideologically motivated violence to further political, social, or religious goals.” NIJ’s focus has been on the radicalization process as it occurs in the United States, regardless of the location of any act of terrorism that may ensue from that process.

Return to text.

Date Published: August 14, 2020