There appear to be no brain imaging studies investigating which brain mechanisms subserve affective, impulsive violence versus planned, predatory violence. It was hypothesized that affectively violent offenders would have lower prefrontal activity, higher subcortical activity, and reduced prefrontal/subcortical ratios relative to controls, while predatory violent offenders would show relatively normal brain functioning. Glucose metabolism was assessed using positron emission tomography in 41 comparisons, 15 predatory murderers, and nine affective murderers in left and right hemisphere prefrontal (medial and lateral) and subcortical (amygdala, midbrain, hippocampus, and thalamus) regions. Affective murderers relative to comparisons had lower left and right prefrontal functioning, higher right hemisphere subcortical functioning, and lower right hemisphere prefrontal/subcortical ratios. In contrast, predatory murderers had prefrontal functioning that was more equivalent to comparisons, while also having excessively high right subcortical activity. Results support the hypothesis that emotional, unplanned impulsive murderers are less able to regulate and control aggressive impulses generated from subcortical structures due to deficient prefrontal regulation. It is hypothesized that excessive subcortical activity predisposes to aggressive behaviour, but that while predatory murderers have sufficiently good prefrontal functioning to regulate these aggressive impulses, the affective murderers lack such prefrontal control over emotion regulation. © 1998 John Wiley & Sons, Ltd.

An open source sample of 111 lone-actor terrorists from the United States and Europe were studied through the lens of the Terrorist Radicalization Assessment Protocol (TRAP-18). This investigative template consists of 8 proximal warning behaviors and 10 distal characteristics for active risk management or active monitoring, respectively, by national security threat assessors. Several aspects of criterion validity were tested in this known outcome sample. Seventy percent of the terrorists were positive for at least half or more of the indicators. When the sample was divided into Islamic extremists, right-wing extremists, and single-issue terrorists, there were no significant differences across all 18 indicators except for 4. When the sample was divided according to successful versus thwarted attackers, the successful attackers were significantly more fixated, creative, and innovative, and failed to have a prior sexually intimate pair bond. They were significantly less likely to have displayed pathway warning behavior and be dependent on a virtual community of likeminded true believers. Effect sizes were small to medium (ϭ 0.190-0.317). The TRAP-18 appears to have promise as an eventual structured professional judgment risk assessment instrument according to some of the individual terrorist content domains outlined by Monahan (2012, 2016).

A new typology of stalking, RECON (relationship and context-based), is proposed, based upon the prior relationship between the pursuer and the victim, and the context in which the stalking occurs. The static typology yields four groups: Intimate, Acquaintance, Public Figure, and Private Stranger. The typology was tested on a large (N = 1005) nonrandom sample of North American stalkers gathered from prosecutorial agencies, a large police department, an entertainment corporation security department, and the authors' files. Interrater reliability for group assignment was 0.95 (ICC). Discriminant validity (p < 0.01) was demonstrated on a variety of demographic, clinical, pursuit, threat, and violence characteristics among and between groups. Findings confirm and extend the work of other researchers, most notably the very high risk of threats and violence among prior sexually intimate stalkers, the very low risk of threats and violence among public figure (celebrity) stalkers, and the negative relationship between stalking violence and psychosis.

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Leakage in the context of threat assessment is the communication to a third party of an intent to do harm to a target. Third parties are usually other people, but the means of communication vary, and include letters, diaries, journals, blogs, videos on the internet, emails, voice mails, and other social media forms of transmission. Leakage is a type of warning behavior that typically infers a preoccupation with the target, and may signal the research, planning, and implementation of an attack. Nomothetic data suggest that leakage occurs in a majority of cases of attacks on and assassinations of public figures, adult mass murders, adolescent mass murders, and school or campus shootings: very low-frequency, but catastrophic acts of intended and targeted violence. Idiographic or case data illustrate the various permutations of leakage. We discuss the operational importance of the concept, place it in the context of other warning behaviors, emphasize the need for further research, and outline risk management strategies for the mitigation of such acts of violence in both law enforcement and clinical mental health settings.

Thirty adult mass murderers and 34 adolescent mass murderers in North America are compared on both offender and offense variables to delineate similarities and differences. Findings indicate a plethora of psychiatric disturbances and odd/reclusive and acting-out personality traits. Predisposing factors include a fascination with weapons and war among many of the adolescents and the development of a "warrior mentality" in most of the adults. Precipitating factors indicate a major rejection or loss in the hours or days preceding the mass murder. Results are interpreted through the lens of threat assessment for targeted violence (Borum, Fein, Vossekuil, & Bergland 1999), recognizing that a fact-based, dynamic behavioral approach is most useful for mitigating risk of such an extremely low-base-rate violent crime.

The Terrorist Radicalization Assessment Protocol (TRAP-18) was utilized to code 2 nonrandom samples of convenience: Subjects who had carried out a lethal terrorist attack in North America between 1993 and 2016 (n ϭ 33), and subjects who were identified as a national security concern, and were either successfully risk managed for at least 2 years, or determined upon investigation to have no intent to mount an attack, were not risk managed, and did not mount an attack during the same period of time (n ϭ 23). The no attack sample was gathered from 2 metropolitan areas in the United States and Canada through law enforcement and mental health counterterrorism investigations. Half the TRAP-18 indicators were found to be significantly different between the samples with medium to large effect sizes ( ϭ .35-.70). The proximal warning behaviors of pathway, identification, energy burst, and last resort were significantly more frequent among the attackers, and directly communicated threat was significantly less frequent. The distal characteristics of ideological framing, changes in thinking and emotion, and creativity and innovation were more frequent among the attackers, and mental disorder was significantly less frequent. The retrospective results are interpreted in the context of other TRAP-18 research, and in relation to other empirical findings concerning lone actor terrorists. Public Significance StatementThe study compares a group of individual terrorists who mounted an attack with a group of individuals who posed a national security concern but did not attack. The instrument for comparison was the Terrorist Radicalization Assessment Protocol (TRAP-18). The instrument worked well in distinguishing the two groups, and should help professional counterterrorism investigators and law enforcement.