Extremism in policing: researching a hidden institutional threat

January 6, 2021, was a day that stunned many Americans and beyond. Approximately 53,000 people attended the “Stop the Steal” rally, a movement falsely alleging fraud in the 2020 US presidential election, while the Federal Bureau of Investigation (FBI) estimated that between 2,000 and 2,500 breached the US Capitol Building to prevent lawmakers from certifying the results (Lucas, 2022). What can best be classified as a riot ensued, which resulted in injuries to approximately 140 officers and the death of one Capitol Police officer (Jackman, 2021). Beyond these numbers, the attack caused widespread destruction inside the Capitol, including broken windows, vandalized offices and damaged historic property, underscoring the chaos officers confronted (Reilly, 2023). This context is important when considering the severity of the injuries sustained by officers, such as Brian Sicknick, who was killed, and the toll the event took on law enforcement personnel. Four additional officers who responded to the attack later died by suicide (Reilly, 2023). While the insurrection itself was alarming, many citizens were even more shocked to learn that police officers from their own communities had participated. As many as 47 current sworn officers from 20 states, as well as the Federal government, were suspected of involvement, not to mention the scores of former and retired officers, prompting urgent questions about the presence of extremist ideologies within the ranks of American law enforcement (Ben-Menachem, 2021).

Extremism in policing is an emerging yet understudied threat to democratic governance, civil rights and institutional legitimacy. This concern is not confined to the United States. Similar challenges have surfaced in other democratic contexts, including Germany, where recent investigations have placed more than 400 state police officers under review for suspected far-right extremist views or conspiracy beliefs (Deutsche Welle, 2024). Other countries, including the United Kingdom (Intelligence and Security Committee of Parliament, 2022), Canada (National Security and Intelligence Committee of Parliamentarians, 2023) and Australia, have likewise documented concerns about extremist infiltration within security institutions, with Australia initiating at least 16 investigations into alleged links between defense personnel and extremist groups (Bogle, 2024).

Although many examples in this article are drawn from the United States, the barriers identified are not unique to the US law enforcement and security institutions in other democratic states face similar challenges, including organizational secrecy, fragmented oversight structures, and definitional ambiguity surrounding extremism. As the recent cases in Germany and Australia demonstrate, extremist beliefs within policing raise comparable concerns about democratic accountability and public trust. The methodological challenges discussed here, and the proposed research strategies, are therefore relevant to scholars studying policing and extremism across national contexts.

Journalists (Bates, 2021; Ben-Menachem, 2021; Kelly, 2021), policymakers (House Committee on Oversight and Reform, 2020; US House of Representatives, 2021) and scholars (Lewandowski and Bumgarner, 2024; Parkin et al., 2021) have increasingly turned their attention to this issue, yet, systematic empirical research remains limited, leaving scholars without reliable baseline estimates or frameworks for understanding the scope of the problem. As Parkin et al. (2021) note, “the number of officers associated with far-right extremism is difficult, if not impossible, to obtain” (p. 15), underscoring the challenge of even establishing the scope of the problem. While extremism encompasses a wide range of ideological movements, we focus primarily on far-right and white supremacist ideologies, as these have been most consistently linked to documented recruitment efforts targeting law enforcement and military. In this research note, we outline why the issue demands urgent scholarly attention, note the barriers to studying it, draw insights from research on extremism in the military, and propose avenues for future inquiry.

This research note makes three contributions to the literature. First, it synthesizes the fragmented or nonexistent discussions of extremism in policing into a coherent conceptual problem, explaining why the phenomenon remains understudied despite increased warnings from analysts and public concern. Second, it adapts established methodological approaches from military research, where similar institutional barriers exist, to the policing context. We thereby demonstrate how researchers can begin to identify credible baseline estimates. Finally, rather than offering a single solution, the article proposes a multi-method research framework that explicitly accounts for detection bias, organizational opacity, and underreporting. In doing so, it moves the conversation beyond whether extremism exists in policing toward how it can be rigorously studied.

In order to discuss extremism, we must first understand how it has been defined. It can be difficult, as extremism is a subjective term and needs a norm by which to measure what is extreme. What is considered extreme in one community may not be in another. As Astrid Bötticher (2017) explains, extremism only exists in relation to the mainstream values of a given society. It reflects a position that rejects core democratic principles such as pluralism, equality and the rule of law, rather than simply challenging political or social institutions. She distinguishes between radicalism, which seeks change within the bounds of democracy, and extremism, which denies the legitimacy of democratic processes altogether. This distinction is important when examining extremism within policing as the danger is not solely officers' private political beliefs. Instead, the concern arises when police practices, organizational norms or occupational culture fail to constrain, or even facilitate, the expression of privately held extremist beliefs in ways that undermine fairness, accountability and respect for the rule of law. Michael Moore, the former chief of the Los Angeles Police Department, illustrates this challenge: “Choosing where to draw this line between free speech and hate speech, between opinions an officer is entitled to and opinions that undermine the department's mission, isn't easy” (Rector and Winton, 2021). It is important to note that the vast majority of police officers do not endorse extremist or exclusionary ideologies. Without systematic and transparent methods for assessing extremist activity, public trust and institutional legitimacy remain vulnerable to both denial and exaggeration.

In policing, most forms of extremism are likely to be social rather than overtly political. More broadly, extremism has been defined as antipluralist and characterized by hostility toward dissent and a rejection of compromise within democratic systems (Lipset and Raab, 1971, see also Mulloy, 2004). This ideology may not involve formal group membership; instead, it may take the form of attitudes or subcultural norms that reinforce racial, gender or cultural hierarchies under the guise of “maintaining order.” While these beliefs may not align with organized extremist movements, they reflect the same intolerance and moral absolutism that define extremism more broadly (Mulloy, 2004). More specifically, far-right extremism is often defined by individuals or groups who are fiercely nationalistic, hold anti-government suspicions and conspiracy theories, and are reverent of individual liberty (Parkin et al., 2021). This can intersect with occupational identities that are centered on law, authority and social control. Understanding extremism in policing, therefore, requires us to see how everyday biases and exclusionary worldviews can function as ideological positions that threaten democratic accountability and equal protection under the law.

This broader understanding of extremism helps clarify how it operates within policing. While few officers publicly align themselves with extremist political movements, some have been spotted wearing pins/patches from groups like the Oath Keepers and the Three Percenters, which are militia organizations identified as far-right extremist groups (Parkin et al., 2021; see, e.g. Rector and Winton, 2021). The profession is not insulated from the social ideologies that often underpin them. Police culture can normalize exclusionary attitudes – toward race, gender, sexuality or dissent – that echo the same antipluralist tendencies scholars associate with extremism (Mulloy, 2004). Southers (2017) describes extremism as rooted in intolerance and moral absolutism, and these traits can surface in policing as rigid “us-versus-them” thinking or an unquestioned belief in the moral virtue of force. As Lowe (2017) argues, the challenge lies in distinguishing constitutionally protected personal beliefs from behaviors that undermine democratic norms. When bias or ideology shapes enforcement decisions, it moves beyond personal opinion and becomes an institutional problem.

The problem is not extremism in itself; a police officer who supports a radical political candidate or holds strong personal beliefs does not inherently threaten democratic values. The concern arises when those beliefs cross into violent extremism or result in disparate treatment of individuals or communities. Southers (2017) notes that violent extremism occurs when ideology is expressed through or used to justify violence. In policing, this violence can take many forms, ranging from overt acts of brutality to unequal enforcement or the systemic targeting of marginalized groups. What makes this particularly troubling is law enforcement's unique position within the state's monopoly on force (Bittner, 1970): when personal ideology shapes the interpretation or application of the law, bias becomes institutional harm. Beyond the immediate harms to individuals and communities, the presence of extremist beliefs within policing undermines the perceived legitimacy of law enforcement institutions themselves. When officers are viewed as acting on ideological beliefs rather than neutral legal authority, public trust erodes and compliance declines (Tyler, 1990).

The FBI has warned for 2 decades that extremist ideologies pose a risk within law enforcement. A 2006 intelligence assessment first documented white supremacist attempts to infiltrate police agencies, followed by a 2015 report noting active links between extremist movements and officers with access to sensitive databases (Federal Bureau of Investigation, 2006; Federal Bureau of Investigation, Counterterrorism Division, 2015). Consistent with these warnings, police departments across the United States continue to grapple with screening for, identifying and addressing officers accused of holding far-right extremist views. This challenge has surfaced in media reporting on departments such as the LAPD and others struggling to draw boundaries around political extremism in their ranks (Rector and Winton, 2021). In a more explicit case, investigative reporting documented cases in which active-duty police officers were discovered to have direct ties to the Ku Klux Klan (KKK), including a Florida officer who simultaneously served as a KKK leader while employed by a municipal police department (The Guardian, 2014). More recent reports indicate that white supremacists continue to seek affiliation with military and police organizations to further their goals (Margolin, 2021). These warnings align with German's (2020) findings that, despite repeated alerts, the federal government has not implemented a national strategy to identify or remove officers affiliated with violent racist or militant groups.

Research confirms that extremist influence poses both internal and external dangers to policing. Parkin et al. (2021) observe that far-right extremism simultaneously targets officers as enemies of the state while also recruiting and radicalizing some within their ranks, threatening both officer safety and organizational legitimacy. Similarly, Jones et al. (2021) report a steady rise in domestic terrorism incidents involving current or former law enforcement officers, mirroring patterns seen among military personnel. Their data show that extremist groups deliberately seek individuals with tactical training and access to weapons and information, making law enforcement officers especially valuable recruits. Together, these findings underscore the urgency of addressing extremist ideologies within policing – not merely as a matter of individual misconduct, but as a growing institutional vulnerability that endangers constitutional protections, community trust and national security.

The growing body of evidence from the military further illustrates why extremist infiltration poses an institutional risk, and why policing scholars should take the study of extremism in policing seriously. A study, conducted by the International Centre for Counter-Terrorism (ICCT), analyzed five years of news coverage and government reporting from twelve Western countries to assess how the right-wing extremist connection to the armed forces poses a risk. The researchers sought to test and refine a theoretical framework outlining five potential risks posed by this nexus. These risks include: (1) military personnel committing acts of right-wing extremist violence; (2) enabling or supporting extremist organizations that engage in such violence; (3) carrying out ideologically motivated hate crimes or violating procedures and rules of engagement while deployed; (4) undermining diversity and inclusion efforts within military institutions and (5) threatening civilian oversight and control of the military (van Dongen et al., 2022). These dynamics mirror concerns raised in the literature on far-right extremism and policing, where individuals with specialized training, state authority and public trust can translate extremist worldviews into actions that threaten organizational legitimacy and equal protection under the law (Lewandowski and Bumgarner, 2024; Mulloy, 2004; Parkin et al., 2021). These similarities underscore that extremism in policing represents a structural risk, much like the challenges documented in the military.

A number of factors impede the ability to study extremism in a law enforcement context. They include limited access and a relative lack of transparency, such as resistance from chiefs and unions, the thin blue line/blue curtain of secrecy ideology, and decentralization of law enforcement, unlike the army. These are not necessarily unique to the study of extremism in policing; however, the sensitivity of the subject matter may exacerbate these impediments. For example, and regarding the decentralization, policing in the United States is comprised of 18,000 different agencies – each with their own hiring and screening criteria, including potentially disqualifying items. This differs from a number of other countries where police forces are much more centralized as opposed to being fragmented. Gaining access to a smaller number of agencies, potentially even nationalized forces, might be easier in these contexts compared to the United States, especially if there is a vested state interest in the study of extremism within the ranks. In terms of access and related to decentralization in the United States, scholars must contend with the fact that these 18,000 police chiefs and other executives are the gatekeepers of their respective departments. Prior police-researcher relationships can help by building trust and building on social capital, but chiefs may deny access to their officers if they do not see value in the topic area – particularly as it relates to officers' potential biases and extremist views. As a result, researchers have been forced to rely on less direct, proxy measures for extremism or the lack thereof.

A national analysis of police archival records in the United States, specifically from departmental websites, found that hiring and screening criteria are often not made accessible to recruits or the public; less than half of the departmental websites list disqualifiers for employment (Kearns et al., 2024). Still, these disqualifiers are indirect and only tangentially related to extremism. There is also no way to address whether and to what extent officers may become radicalized following the recruitment and hiring periods. Additionally, there are ethical constraints, primarily the need to protect recruits' anonymity while balancing the need to weed out those with criminal, unethical and unprofessional background and ideologies. Finally, definitional ambiguity prevents a parsimonious and easily agreed-upon set of standards on which to assess and quantify extremists in policing. One department's or state's Peace Officers Standards and Training (POST) and equivalent entities' definition of extremism will vary from the next. There is currently no list of domestic terrorist groups according to official government organizations in the United States; only the Southern Poverty Law Center (SPLC) and the Anti-Defamation League (ADL) define hate groups.

Importantly, these barriers are not unique to the study of extremism. Similarly, methodological challenges have long confronted scholars examining racial bias in policing. Regarding the latter, although there is clear and convincing evidence of racial disparities in policing outcomes (e.g. stops and post-stop outcomes; use of force), it is difficult to test and state definitively whether those disparities are due to officers' prejudices/biases. Two reviews by Kahn and Martin (2016, 2020) offer insight into the challenges of studying racial bias in policing, which can be subsequently applied to extremism in policing. For one, researchers often lack the requisite data and measures to rule out alternative explanations – including factors that may covary and interact with race – for the racial/ethnic disparities that exist. As a result, relatively little is known about the causal role that officers' attitudes toward racial/ethnic minorities impacts behavior (Kahn and Martin, 2016, 2020). Similar to trying to estimate racial bias, conducting research on extremism in policing is fraught with establishing accurate base rates and appropriate comparison groups.

Research on extremism within the military offers a useful comparative framework. Examining the military is especially useful because, like law enforcement, it is a hierarchical, uniformed institution with a mandate to wield state-sanctioned force, making concerns about extremism within its ranks comparable. Although observers such as Beirich (2020) and Smith and Dearen (2024) argue that the military's response has been uneven, these efforts nonetheless provide insight into how large organizations attempt to identify and address problem. A first step is simply understanding the nature of the threat. A recent analysis finds that a significant share of individuals who committed extremist crimes in the United States previously served in the military (Jensen et al., 2024). This pattern aligns with broader evidence documenting the presence of extremist attitudes and behaviors within the force. As Beirich's (2020) testimony recounts, Military Times polls from 2017 to 2019 show that many active-duty service members reported witnessing white nationalist symbols, racist language, and other ideologically motivated harassment (Shane III, 2020). Federal agencies have likewise noted that white supremacist groups actively recruit current and former military members. Taken together, these findings reveal longstanding institutional vulnerabilities that help explain why some domestic extremists have military backgrounds.

One major strand of research on extremism in the military relies on analyzing known offenders in order to identify patterns that may illuminate future risk. These studies begin with individuals who have already engaged in extremist activity and work backward to understand their service histories, demographic traits, and pathways into radicalization. Among the most comprehensive is the National Consortium for the Study of Terrorism and Responses to Terrorism's (START) Radicalization in the Ranks, which uses a large, systematically compiled auxiliary dataset of all publicly identified US extremist offenders with military experience from 1990 to 2023 (Jensen et al., 2024). Drawing exclusively from open sources, including court filings, police reports and news accounts, this approach allows researchers to track long-term trends, compare military and nonmilitary extremists, and examine service-related variables such as branch, discharge type, deployment history, combat exposure and indicators of in-service radicalization. By identifying recurring patterns in ideology, behavior and risk factors, the START analysis demonstrates how incident-level data can be leveraged to understand insider threats at scale.

In addition to the ICCT study mentioned earlier, a third example comes from Milton and Mines (2021), who analyze publicly available arrest and charging documents for January 6 defendants with military backgrounds. They found that veterans made up the overwhelming majority of military-linked participants and were disproportionately represented in organized extremist groups. This shows how open-source event-driven datasets can reveal organizational ties, subgroup concentrations and the conditions under which military skills or identities become operationalized in extremist contexts. All three studies illustrate how patterns observed among past offenders may foreshadow future mobilization risks, especially among veterans navigating the transition to civilian life.

Taken together, these three studies demonstrate the utility of offender-based research for understanding extremism within military populations. By reconstructing the characteristics and trajectories of those who have already engaged in extremist crimes, researchers are able to identify service-related vulnerabilities, behavioral indicators and organizational dynamics that may otherwise remain hidden. This body of work thereby establishes a foundation for anticipating potential risks and designing institutional responses. Building on these offender-centered approaches, other research traditions, such as survey analyses, qualitative testimony and federal threat assessments, provide additional perspectives on how extremism manifests within the ranks and how institutions understand the problem beyond known offenders.

Second, national surveys, including the RAND survey and the repeated Military Times polls, capture service members' self-reported experiences with white nationalism, racist harassment and extremist symbols, offering insight into the everyday climate that may enable or normalize extremist attitudes (Helmus et al., 2023; Shane III, 2020). Although conducted by a news organization rather than the military itself, the Military Times surveys' voluntary and confidential format provides a level of candor that institutional reporting mechanisms often cannot, particularly in environments where service members may fear retaliation for reporting misconduct. The RAND study, on the other hand, assessed veterans' support for extremist groups and willingness to endorse political violence, offering a quantitative measure of ideological sympathies that could facilitate radicalization. These surveys also illuminate a broader range of behaviors than official disciplinary records, which reflect only those incidents that are detected and formally addressed. While many expressions of white nationalism fall short of violent extremism, understanding their prevalence is essential for assessing the ideological landscape in which radicalization can take root.

Third, a Pentagon-commissioned empirical study has examined extremist activity within security institutions using mixed methods. The Institute for Defense Analyses (IDA) (2022) combined extensive policy and document review, analysis of publicly reported extremist incidents involving service members and examination of internal Department of Defense (DoD) disciplinary and personnel data systems. The researchers also conducted interviews and site visits across multiple military branches to assess how extremist activity is understood, detected and addressed in practice. However, subsequent reporting has criticized the study's reliance on dated administrative data, arguing that such sources may underestimate the scope of extremist activity within the military (Smith and Dearen, 2024).

Finally, assessments conducted by both federal and independent agencies such as the FBI and Department of Homeland Security (DHS) have identified recruitment strategies used by extremist groups to target military personnel and outline security vulnerabilities specific to military and law enforcement environments while the DoD has looked more closely at identifying and screening strategies (Federal Bureau of Investigation, 2008; Office of the Under Secretary of Defense for Personnel and Readiness, 2021; U.S. Department of Homeland Security, Office of Intelligence and Analysis, 2009; Defense Personnel and Security Research Center [PERSEREC], 2021). For example, the DoD determined that a lexicon of terms can be used to detect white supremacy activity among incident reports in the Joint Personnel Adjudications System, the DoD's system of record for personnel security information (PERSEREC, 2021). While these assessments focus on documented threats, civil society organizations such as the Southern Poverty Law Center (SPLC) have been able to identify and monitor white supremacists and other extremists serving in the military. Based on the testimony of Heidi Beirich, co-founder of the Global Project Against Hate and Extremism, extremist groups have long viewed military service members and veterans as high-value recruits, specifically because they have tactical training and they convey legitimacy to the organization, making recruitment easier (Beirich, 2021). Although these agencies have not posted a formal methodological design, sources indicate that the SPLC has analyzed leaked membership lists and open-source intelligence to identify current extremists in the military (Independent Lens, 2016).

Recent efforts within the US Department of Defense (D.O.D.) illustrate how research on extremism within the military can inform organizational response. Following the January 6, 2021 attack on the US Capitol, the D.O.D. established the Countering Extremist Activity Working Group (CEAWG) to assess the scope of prohibited extremist activity and to develop both immediate and longer-term recommendations (U.S. Department of Defense, 2021). Drawing on analyses from the National Consortium for the Study of Terrorism and Responses to Terrorism (START), internal data, and consultations with subject-matter experts, the CEAWG produced a formal report outlining revisions of the definitions or prohibited activity, enhancements to screening procedures, expanded training initiatives and reforms to insider-threat program reforms. These research-informed efforts translated into concrete institutional changes, including updated screening practices and the commissioning of additional empirical studies to assess extremist activity within the department (Doxsee and Macander, 2022).

Taken together, military-focused research illustrates how extremism within security institutions can be examined through multiple, overlapping lenses, including offender-based analyses, survey research, commissioned institutional studies and investigative or open-source methods. Given the structural similarities between the military and law enforcement and the significant flow of veterans into policing, these methodological strategies provide a useful foundation for designing empirical research on extremism within police agencies. In the next section, we outline how each of these approaches can be adapted, or have already started to be adapted, to the policing context.

The military's response illustrates that research on extremism can change policy and practice, not just document the risk. Similar to the US Department of Defense response, downstream applications are conceivable in the policing context. Findings from research into extremism in policing could inform screening criteria, targeted training for supervisors as well as personnel to be able to identify warning signs, and centralized data collection efforts across decentralized agencies. As with the military, these applications would require a commitment on the behalf of leadership and attention to civil liberties.

Extremism in law enforcement has received little empirical examination - largely due to the aforementioned barriers to research. Aside from reporting on select agencies (e.g. Los Angeles County Sheriff's Department; Wenzke, 2024) or by independent investigations (e.g. The Plain View Project, n.d.), we are unaware of any published study that has attempted to quantify the prevalence of white nationalism ideology in policing. Much of the existing literature is descriptive rather than empirical. For example, Johnson (2019) identifies more than 100 police departments from over 40 states where police officers sent overtly racist emails, texts or made racist comments via social media. However, this work is argumentative rather than systematic; it does not employ a defined methodology to estimate prevalence. Instead, Johnson uses these incidents to argue that explicit white supremacist ideology is a serious issue in policing and that expanded use of the Brady doctrine, which mandates that prosecutors must disclose any evidence that is favorable to the defense, could increase transparency and institutional accountability.

Following the January 6th insurrection, and after the information that nearly 50 current law enforcement officers participated (see Ben-Menachem, 2021), DHS put out an open solicitation for grant proposals to study extremism in policing. We are aware of two grant recipients and their methods. Both Kearns et al. (2024) and Harris et al. (2021) employed archival analyses of departmental websites and policies, respectively. They also both conducted national surveys of police departments; yet, neither derived direct measures of extremism within the ranks of American policing – further highlighting the challenges of the subject matter. Overall, the studies found substantial agency-level variation in the transparency as well as the rigor of hiring and screening criteria, although departments generally require that recruits disclose involvement in and/or tattoos associated with groups of concern. However, most agencies surveyed indicate that they do not monitor officers' social media use, and one-half do not have a specific policy to address insider threats. Interestingly, most departments perceived either no or a low risk from extremist groups of concern or insider threats; instead, departments expressed greater concern for officers' alcohol and gambling abuse (Kearns et al., 2024).

A similar, multi-method approach – like that of the military – could strengthen efforts to understand extremism in policing. As with the military, no single data source is sufficient, but combining several provides a clearer picture. Quantitative analyses of criminal and disciplinary cases involving officers, similar to the START approach, could help establish baseline estimates of extremist involvement. Researchers can start with individuals who have already engaged in violence or other extremist activity, working back retroactively to discern more information about their pathways to radicalization. One high-profile example is that of former LAPD officer and Navy Reservist Christopher Dorner, who shot and killed four police officers and their family members, while wounding another three in 2013 before committing suicide (Kelly, 2013). After being terminated by the LAPD, Dorner wrote and posted a manifesto on social media where he declared “unconventional and asymmetric warfare” on the LAPD and their families unless the department publicly admitted that he was fired in retaliation for reporting on excessive force. While most entries will not include current/former officers who committed mass or spree-style shootings, this methodological approach can be used for the aforementioned 47 current police officers who took part in the January 6th insurrection (Ben-Menachem, 2021) or those identified in other open-sourced datasets, such as The Plain View Project. Still, this methodology would only capture police officers who have engaged in extremist activity, which would result in a potentially biased subsample that undercounts the true nature of the problem.

Anonymous surveys, modeled on the Military Times polls, could also capture officers' firsthand experiences with bias, extremist symbols or ideologically motivated behavior within their departments. There is no shortage of professional law enforcement or research organizations that are capable of conducting these types of surveys. They include the International Association of Chiefs of Police, the National Policing Institute and the Police Executive Research Forum, among others. Even trade publications, such as Police1 and Law Enforcement Today, could survey active and former members about their perceptions of and experiences with extremism within their departments and the profession more broadly. These efforts can also be scaled up to include thousands of police officers by organizations that regularly engage in public opinion polling. For example, the Pew Research Center surveyed nearly 8,000 police officers in 2016 for a project titled “Behind the Badge” (see Morin et al., 2017). This survey questionnaire asked about sensitive topics, such as racial differences among officers, perceived relationships with minority community members, etc. Similar surveys administered by any of these organizations regarding extremism in policing would certainly be welcomed efforts on an often-neglected and under-researched topic.

While such surveys may be a crucial first step in identifying police officers who have extremist views, scholars should also ask a number of questions to measure and assess potential correlates with those views. For example, survey questionnaires can include a number of items regarding police officers' backgrounds/upbringing, exposure and contact with minority groups, the racial/ethnic composition of the department, media consumption and what types of outlets they visit for news and current events (see, e.g. Shjarback, 2022), etc. These measures can be used to identify associations with extremists opinions, which may inform agencies' ability to prevent and combat such views.

It has now been five years since the January 6th insurrection at the US Capitol, where nearly 50 current sworn law enforcement officers were suspected of participating. And while groups like the FBI have been sounding the alarm for 2 decades that extremist ideologies pose a risk within American law enforcement, January 6th, 2021 served as the most recent cautionary tale. In the years since, DHS prioritized research on extremism in policing (see Harris et al., 2021; Kearns et al., 2024) - including how to better screen for and identify insider threats. However, the topic has emerged in the United States as well as the United Kingdom, Germany, Canada and Australia alike; extremism in policing remains an understudied and underdeveloped threat to democratic governance, civil rights and institutional legitimacy. Systematic empirical research remains limited, leaving scholars without reliable baseline estimates or frameworks for understanding the scope of the problem. Preventing those with extremist ideology and, more tangibly, connections to and membership in extremist groups from entering law enforcement ranks is critically important.

We set out to accomplish a few tasks in this research note. They include synthesizing a fragmented literature on the topic, while providing an impetus to continue to study extremism in policing. Fortunately, scholars have a road map in the form of established methodological approaches from similar research efforts on the military, despite the barriers and impediments to rigorously examining such a sensitive area of focus. We implore researchers to adapt such methods and analyses to not only begin to identify credible baseline estimates of extremism in policing, but also to better understand the pathways and correlates of such beliefs. Only through sustained, systematic empirical inquiry can scholars and policymakers begin to understand the true scope of extremist activity within policing and safeguard the democratic institutions that those agencies are meant to protect.