This article analyzes the sociodemographic network characteristics and antecedent behaviors of 119 lone‐actor terrorists. This marks a departure from existing analyses by largely focusing upon behavioral aspects of each offender. This article also examines whether lone‐actor terrorists differ based on their ideologies or network connectivity. The analysis leads to seven conclusions. There was no uniform profile identified. In the time leading up to most lone‐actor terrorist events, other people generally knew about the offender's grievance, extremist ideology, views, and/or intent to engage in violence. A wide range of activities and experiences preceded lone actors' plots or events. Many but not all lone‐actor terrorists were socially isolated. Lone‐actor terrorists regularly engaged in a detectable and observable range of activities with a wider pressure group, social movement, or terrorist organization. Lone‐actor terrorist events were rarely sudden and impulsive. There were distinguishable behavioral differences between subgroups. The implications for policy conclude this article.

We test whether significant differences in mental illness exist in a matched sample of lone- and group-based terrorists. We then test whether there are distinct behavioral differences between lone-actor terrorists with and without mental illness. We then stratify our sample across a range of diagnoses and again test whether significant differences exist. We conduct a series of bivariate, multivariate, and multinomial statistical tests using a unique dataset of 119 lone-actor terrorists and a matched sample of group-based terrorists. The odds of a lone-actor terrorist having a mental illness is 13.49 times higher than the odds of a group actor having a mental illness. Lone actors who were mentally ill were 18.07 times more likely to have a spouse or partner who was involved in a wider movement than those without a history of mental illness. Those with a mental illness were more likely to have a proximate upcoming life change, more likely to have been a recent victim of prejudice, and experienced proximate and chronic stress. The results identify behaviors and traits that security agencies can utilize to monitor and prevent lone-actor terrorism events. The correlated behaviors provide an image of how risk can crystalize within the individual offender and that our understanding of lone-actor terrorism should be multivariate in nature.

Research Summary: Public interest and policy debates surrounding the role of the Internet in terrorist activities is increasing. Criminology has said very little on the matter. By using a unique data set of 223 convicted United Kingdom–based terrorists, this article focuses on how they used the Internet in the commission of their crimes. As most samples of terrorist offenders vary in terms of capabilities (lone‐actor vs. group offenders) and criminal sophistication (improvised explosive devices vs. stabbings), we tested whether the affordances they sought from the Internet significantly differed. The results suggest that extreme‐right‐wing individuals, those who planned an attack (as opposed to merely providing material support), conducted a lethal attack, committed an improvised explosive device (IED) attack, committed an armed assault, acted within a cell, attempted to recruit others, and engaged in nonvirtual network activities and nonvirtual place interactions were significantly more likely to learn online compared with those who did not engage in these behaviors. Those undertaking unarmed assaults were significantly less likely to display online learning. The results also suggested that extreme‐right‐wing individuals who perpetrated an IED attack, associated with a wider network, attempted to recruit others, and engaged in nonvirtual network activities and nonvirtual place interactions were significantly more likely to communicate online with co‐ideologues. Policy Implications: Collectively the results provide insight into violent radicalization as a whole and not just into violent online radicalization. The results also largely confirm the results found in von Behr, Reding, Edwards, and Gribbon (2013) and in Gill and Corner (2015). The current study and the two previous studies have tackled these questions by using numerous methodological approaches and data sources and have arrived at similar conclusions. The Internet is largely a facilitative tool that affords greater opportunities for violent radicalization and attack planning. Nevertheless, radicalization and attack planning are not dependent on the Internet, and policy needs to look at behavior, intentions, and capabilities and not just at beliefs. From a risk assessment perspective, the study also highlights the fact that there is no easy offline versus online violent radicalization dichotomy to be drawn. It may be a false dichotomy. Plotters regularly engage in activities in both domains. Often their behaviors are compartmentalized across these two domains. Threat management policies would do well to understand the individuals’ breadth of interactions rather than relying on a dichotomous understanding of offline versus online, which represent two extremes of a spectrum that regularly provide prototypical examples in reality. A preoccupation with only checking online behaviors may lead an intelligence analyst to miss crucial face‐to‐face components of a plot's technical development or a perpetrator's motivation. Policy and practice may benefit from adopting insights from emerging research arguing in favor of disaggregating our conception of the “terrorist” into discrete groups (e.g., foreign fighters vs. homegrown fighters, bomb‐makers vs. bomb‐planters, and group‐actors vs. lone‐actors; Gill and Corner, 2013; LaFree, 2013) rather than disaggregating the radicalization process into discrete groups (e.g., online radicalization and prison radicalization). We need to understand the drives, needs, and forms of behavior that led to the radicalization and attack planning and why the offender chose that environment rather than purely looking at the affordances the environment produced. By looking at the Internet as an affordance opportunity that some forms of terrorist or terrorist violence require more than others do, the focus is shifted from the radicalization process toward an understanding of how crimes are committed. In other words, we are looking at crime events rather than at the underlying dispositions behind the criminality.

This book provides the first empirical analysis of lone-actor terrorist behaviour. Based upon a unique dataset of 111 lone actors that catalogues the life span of the individual’s development, the book contains important insights into what an analysis of their behaviours might imply for practical interventions aimed at disrupting or even preventing attacks. It adopts insights and methodologies from criminology and forensic psychology to provide a holistic analysis of the behavioural underpinnings of lone-actor terrorism. By focusing upon the behavioural aspects of each offender and by analysing a variety of case studies, including Anders Breivik, Ted Kaczynski, Timothy McVeigh and David Copeland, this work marks a pointed departure from previous research in the field. It seeks to answer the following key questions: Is there a lone-actor terrorist profile and how do they differ? What behaviours did the lone-actor terrorist engage in prior to his/her attack and is there a common behavioural trajectory into lone-actor terrorism? How ‘lone’ do lone-actor terrorists tend to be? What role, if any, does the internet play? What role, if any, does mental illness play? This book will be of much interest to students of terrorism/counter-terrorism studies, political violence, criminology, forensic psychology and security studies in general.

This study analyzes the effects of conspiracy beliefs on violent extremist intentions. More specifically, we investigate whether the relationship between conspiracy beliefs and violent extremism depends upon individual characteristics such as varying levels of self-efficacy, self-control, and law-relevant morality. Variable interactions examine where conspiracy beliefs exert strong effects on violent extremist intentions. The analysis is based on a German nationally representative survey (N = 1502). To our knowledge, it is the first and only nationally representative survey carried out in violent extremism research. Our results confirm that a stronger conspiracy mentality leads to increased violent extremist intentions. However, this relationship is contingent on several individual differences. The effects are much stronger for individuals exhibiting lower self-control, holding a weaker law-relevant morality, and scoring higher in self-efficacy. Conversely, when stronger conspiracy beliefs are held in combination with high self-control and a strong law-relevant morality, violent extremist intentions are lower. Such individual features thus constitute interactive protective factors for violent extremism. These results have important implications for practice in the area of violent extremism risk assessment and management. Conceptually, the results demonstrate the need to further elaborate the conditional effects of certain risk as well as protective factors for violent extremism.