Sexual offences by multiple perpetrators are more violent and involve more severe forms of sexual violation than those perpetrated by a lone offender. Often a clear leader exists within these groups. Questions have been raised as to the relative risk of reoffending and the potentially differing criminogenic needs of leaders and followers. However, a recent study comparing leaders and followers in juvenile multiple perpetrator rapes (t'Hart-Kerkhoffs et al., 2011) failed to find some of the expected differences. It was proposed that this might be due, in part, to the way leaders and followers were classified in the study. Before work can progress in this area, it is important to devise reliable and valid means of identifying leaders and followers in multiple perpetrator rape. This article reports on a study which investigated the utility of two different methods of identifying leadership. The Scale of Influence (Porter & Alison, 2001) was applied to a sample of 256 offenders responsible for 95 multiple perpetrator rapes from the United Kingdom. Following this, the relative number of directives uttered by offenders was used to designate leadership. In 66% of the offences sampled, a leader was designated using the number of directives uttered compared with 80% when using the Scale of Influence. When combining both measures to form a composite measure of leadership, this percentage increased to 89%. Classifications of offenders as leaders, followers, and neither, according to the Scale of Influence, the count of directives, and the composite measure, were compared with classifications made by a practitioner to assess their concordance. The composite measure showed the greatest agreement with practitioner opinion. These findings suggest that the Scale of Influence could be developed to take account of other ways that leadership is displayed during multiple perpetrator rapes.

There is little empirical research examining the reasons behind multiple perpetrator sexual offending. A limited number of studies provide reasons for offending offered by perpetrators of this type of sexual violence, but only one published study exists where these perpetrators were interviewed regarding their offense. The Multi-Factorial Model of Multiple Perpetrator Sexual Offending (MPSO) proposed that various factors (individual, sociocultural, and situational) play a role in this type of sexual assault, noting in particular the importance of group dynamics and processes. In the current study, 25 convicted perpetrators of multiple perpetrator sexual offending housed in educational centers and prisons in Portugal were interviewed about their involvement and reasons for participating in the offense. The findings suggested that group processes and dynamics play an important part in this type of sexual offending. Furthermore, the results provided some evidence to support the factors proposed by the Multi-Factorial Model of MPSO. These findings have implications for prevention and treatment programs and for the assessment of offenders.

The effect of number of perpetrators involved in multiple perpetrator rapes on offense characteristics is underresearched despite beliefs that duos/dyads differ in their interactions and dynamics to groups of 3+ members. We analyzed a national sample of 336 allegations of completed and attempted rape of female victims from the United Kingdom. Rapes committed by multiple (duos and groups of 3+ perpetrators) and lone offenders were compared on offense characteristics (incorporating the approach, maintenance, and closure phases of each rape) and victim and offender sociodemographic characteristics. Significant differences between rapes committed by lone, duo, and 3+ group offenders were found for the age and ethnicity of the offenders; the type of approach used; the locations of the initial contact, assault, and release of the victims; the use of a vehicle; the precautions utilized; the verbal themes present; and the sex acts performed. These results have implications for educational prevention programs and interventions with offenders.

Background: Recent scientific work proved that knowledge about body composition beyond the body mass index is essential. Both adipose tissue and muscular status are determining risk factors of morbidity and mortality. Analysis of single cross-sectional computed tomography (CT) images, acquired during routine care only to prevent additional radiation exposure, provide a detailed insight into the body composition of chronically and critically ill patients. Methods: This retrospective study included 490 trauma patients of whom a whole-body multiple detector CT scan was acquired at admission. From a single cross-sectional CT, we compared eight diametric and planimetric techniques for the assessment of core muscle mass as well as visceral and subcutaneous adipose tissue. Furthermore, we derived formulas for converting the measurement results of various techniques into each other. Results: For intra- and interobserver reliability, we obtained intraclass correlation coefficients (ICCs) ranging from 0.947 to 0.997 (intraobserver reliability) and from 0.850 to 0.998 (interobserver reliability) for planimetric measurements. Diametric techniques conferred lower ICCs with 0.851–0.995 and 0.833–0.971, respectively. Overall, area-based measurements of abdominal adipose tissue yielded highly correlated results with diametric measures of obesity. For example, the Pearson correlation of visceral adipose tissue and sagittal abdominal diameter was 0.87 for male and 0.82 for female patients. Planimetric and diametric muscle measurements correlated best for lean psoas area and bilateral diametric measurement of the psoas with a Pearson correlation of 0.90 and 0.93 for male and female patients, respectively. Conclusion: Planimetric measurements should remain the gold standard to describe fat and muscle compartments. Diametric measurements could however serve as a surrogate if planimetric techniques are not readily available or feasible as for example in large registries.