Multiagency responses to reduce radicalisation often involve collaborations between police, government, nongovernment, business and/or community organisations. The complexities of radicalisation suggest it is impossible for any single agency to address the problem alone. Police‐involved multiagency partnerships may disrupt pathways from radicalisation to violence by addressing multiple risk factors in a coordinated manner.
• 1. Synthesise evidence on the effectiveness of police‐involved multiagency interventions on radicalisation or multiagency collaboration
• 2. Qualitatively synthesise information about how the intervention works (mechanisms), intervention context (moderators), implementation factors and economic considerations.
Terrorism‐related terms were used to search the Global Policing Database, terrorism/counterterrorism websites and repositories, and relevant journals for published and unpublished evaluations conducted 2002–2018. The search was conducted November 2019. Expert consultation, reference harvesting and forward citation searching was conducted November 2020.
Eligible studies needed to report an intervention where police partnered with at least one other agency and explicitly aimed to address terrorism, violent extremism or radicalisation. Objective 1 eligible outcomes included violent extremism, radicalisation and/or terrorism, and multiagency collaboration. Only impact evaluations using experimental or robust quasi‐experimental designs were eligible. Objective 2 placed no limits on outcomes. Studies needed to report an empirical assessment of an eligible intervention and provide data on mechanisms, moderators, implementation or economic considerations.
Data Collection and Analysis
The search identified 7384 records. Systematic screening identified 181 studies, of which five were eligible for Objective 1 and 26 for Objective 2. Effectiveness studies could not be meta‐analysed, so were summarised and effect size data reported. Studies for Objective 2 were narratively synthesised by mechanisms, moderators, implementation, and economic considerations. Risk of bias was assessed using ROBINS‐I, EPHPP, EMMIE and CASP checklists.
One study examined the impact on vulnerability to radicalisation, using a quasi‐experimental matched comparison group design and surveys of volunteers (n = 191). Effects were small to medium and, aside from one item, favoured the intervention. Four studies examined the impact on the nature and quality of multiagency collaboration, using regression models and surveys of practitioners. Interventions included: alignment with national counterterrorism guidelines (n = 272); number of counterterrorism partnerships (n = 294); influence of, or receipt of, homeland security grants (n = 350, n = 208). Study findings were mixed. Of the 181 studies that examined mechanisms, moderators, implementation, and economic considerations, only 26 studies rigorously examined mechanisms (k = 1), moderators (k = 1), implementation factors (k = 21) or economic factors (k = 4).
All included studies contained high risk of bias and/or methodological issues, substantially reducing confidence in the findings.
A limited number of effectiveness studies were identified, and none evaluated the impact on at‐risk or radicalised individuals. More investment needs to be made in robust evaluation across a broader range of interventions.
Qualitative synthesis suggests that collaboration may be enhanced when partners take time to build trust and shared goals, staff are not overburdened with administration, there are strong privacy provisions for intelligence sharing, and there is ongoing support and training.