Examining Radicalization's Risk and Protective Factors: A Case-Control Study of Violent Extremists, Non-Violent Criminal Extremists, Non-Offending Extremists, and Regular Violent Offenders, United States, 1990-2020 (ICPSR 39026)

Version Date: Aug 14, 2025

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Principal Investigator(s):
Steven M. Chermak, Michigan State University; Joshua D. Freilich, John Jay College of Criminal Justice; Arun Ross, Michigan State University

https://doi.org/10.3886/ICPSR39026.v1

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Summary

This project examined the multidimensional pathways that led to extremism and extremist behaviors. The focus of the research was to examine risk and protective factors that either directly, or in combination, interact to increase or mitigate the risk of radicalization and terrorism.

This project comparatively examined the presence/absence of risk and protective factors across three groups:

  1. extremist individuals who committed ideologically motivated violent (fatal and non-fatal violent attacks) and nonviolent (financial) crimes
  2. extremists who did not break the law and only engaged in legal extremist activities
  3. persons who committed non-ideological motivated homicides and other violent attacks

Thus, researchers accomplished four major goals/objectives in this project. First, although there has been a good amount of radicalization and risk assessment-related research on risk and protective factors, researchers expanded this work with comparative analyses that have not been previously explored. Second, few studies compared violent or nonviolent criminal extremists to nonoffending extremists or other types of violent offenders. Third, researchers used a case-control approach to provide an empirically robust understanding of categorical differences across groups that have not yet been achieved. Fourth, researchers examined differences in participation of warning behaviors across the groups studied.

The data file includes 971 cases.

Citation

Chermak, Steven M., Freilich, Joshua D., and Ross, Arun. Examining Radicalization’s Risk and Protective Factors: A Case-Control Study of Violent Extremists, Non-Violent Criminal Extremists, Non-Offending Extremists, and Regular Violent Offenders, United States, 1990-2020. Inter-university Consortium for Political and Social Research [distributor], 2025-08-14. https://doi.org/10.3886/ICPSR39026.v1

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Funding

United States Department of Justice. Office of Justice Programs. National Institute of Justice (2020-ZA-CX-0001)

Subject Terms

Geographic Coverage

Restrictions

Access to these data is restricted. Users interested in obtaining these data must complete a Restricted Data Use Agreement, specify the reasons for the request, and obtain IRB approval or notice of exemption for their research.

Distributor(s)

Inter-university Consortium for Political and Social Research
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Time Period(s)

1990 -- 2020

Date of Collection

2021-01 -- 2023-12
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Study Purpose

Research questions focused on exploring differences in risk and protective factors across important dimensions.

  1. How does the presence of risk and protective variables vary when comparing violent ideological offenders to nonviolent criminal ideological offenders?
  2. How does the presence of risk and protective variables vary when comparing ideological offenders to nonoffending extremists?
  3. How does the presence of risk and protective variables vary when comparing ideological homicide offenders to regular homicide offenders?
  4. How does the presence of risk and protective variables vary when comparing jihadist, far right, and far left extremists?
  5. How does the presence of risk and protective variables vary when comparing jihadist, far right, and far left ideological offenders to jihadist, far right, and far left noncriminal extremists?
  6. How do indicators of extremist mobilization vary by the violent/non-violent ideological extremists and across type of ideological motivation (jihadist, far right, far left)?

Study Design

Researchers used the United States Extremist Crime Database (ECDB) to identify the violent and nonviolent offenders for the study, and then used a case control methodology to identify the nonoffending extremists and the regular violent offenders. Researchers then updated the case source files for the ECDB cases, and systemically collected open-source documents on the nonoffending extremist and regular violent offender groups. Researchers used the source file documents to code risk and protective factors.

Sample

The violent and nonviolent extremists were selected from the United States Extremist Crime Database (ECDB).

For the first control group, non-extremist violent offenders who met the demographic, geographic, and temporal parameters were identified using open-source methodologies. Violent crimes are generally newsworthy events and thus, researchers set search parameters for county and time period. Researchers then identified five control events where the perpetrator's age and gender were reported. Researchers then randomly selected one of these events as a control. If, during this process, it was determined that the individual did not fit the researchers' inclusion criteria for a control (e.g., researchers found the individual was not connected to the offense or did not meet the demographic characteristics used to identify the researchers' control groups), researchers replaced the individual with the next person in the sampling frame. When researchers were unable to find an adequate number of control cases, researchers extended the time period and/or the geographic region (adjacent counties) to identify additional possibilities. Importantly, the goal of the researchers' approach was not to match the cases and controls one for one, but to have the sample of the controls approximate the researchers' population of extremists.

For the second control group, non-offenders who had been radicalized, researchers similarly used open-source data methodologies to identify individuals with extremist beliefs who lived in the same locations and were active during the same periods as the extremist criminal offenders. Researchers used several different open sources to generate potential controls. For example, news media frequently cover protest events and marches. Thus, leaders and members of Klan groups, militia organizations, and neo-Nazi groups would be identified in these articles. Scholars and policy-focused groups often discuss the activities of groups of different ideologies and highlight active individuals in such groups. Moreover, researchers supplemented with social media searches to identify individuals who publicly aligned themselves with the extremist ideologies studied.

Time Method

Cross-sectional

Universe

Extremists who committed either violent or nonviolent crimes between 1990 and 2020.

Unit(s) of Observation

Individuals

Data Source

United States Extremist Crime Database (ECDB)

Data Type(s)

Mode of Data Collection

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Original Release Date

2025-08-14

Version History

2025-08-14 ICPSR data undergo a confidentiality review and are altered when necessary to limit the risk of disclosure. ICPSR also routinely creates ready-to-go data files along with setups in the major statistical software formats as well as standard codebooks to accompany the data. In addition to these procedures, ICPSR performed the following processing steps for this data collection:

  • Created variable labels and/or value labels.
  • Checked for undocumented or out-of-range codes.

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Notes

  • The public-use data files in this collection are available for access by the general public. Access does not require affiliation with an ICPSR member institution.

  • One or more files in this data collection have special restrictions. Restricted data files are not available for direct download from the website; click on the Restricted Data button to learn more.