Legitimacy in Policing: A Systematic Review
Authors: Mazerolle Lorraine , Bennett Sarah , Davis Jacqueline , Sargeant Elise , Manning Matthew 
Published: January 2013

This Campbell systematic review assesses the direct and indirect benefits of public police interventions that use procedurally just dialogue. The review summarises findings from 30 studies conducted in Australia, the USA and England. The participants were individuals (citizen, victim, offender etc.), groups (e.g. community) and third parties (e.g. religious advisors).Police‐led interventions specifically aimed at increasing legitimacy have a significant impact on public satisfaction with and confidence in the police. Such interventions are also associated with significantly increased public compliance/cooperation, procedural justice (fairness, neutrality, etc.) and legitimacy (obligation to obey police/law). Interventions also had a minor effect on reoffending.Executive Summary/AbstractBACKGROUNDPolice require voluntary cooperation from the general public to be effective in controlling crime and maintaining order. Research shows that citizens are more likely to comply and cooperate with police and obey the law when they view the police as legitimate. The most common pathway that the police use to increase citizen perceptions of legitimacy is through the use of procedural justice. Procedural justice, as described in the literature, comprises four essential components. These components are citizen participation in the proceedings prior to an authority reaching a decision (or voice), perceived neutrality of the authority in making the decision, whether or not the authority showed dignity and respect toward citizens throughout the interaction, and whether or not the authority conveyed trustworthy motives.Police departments throughout the world are implicitly and explicitly weaving the dialogue of these four principles of procedural justice (treating people with dignity and respect, giving citizens “voice” during encounters, being neutral in decision making, and conveying trustworthy motives) into their operational policing programs and interventions.OBJECTIVESThis review synthesizes published and unpublished empirical evidence on the impact of interventions led by the public police to enhance citizen perceptions of police legitimacy. Our objective is to provide a systematic review of the direct and indirect benefits of policing approaches that foster legitimacy in policing that either report an explicit statement that the intervention sought to increase legitimacy or report that there was an application of at least one of the principles of procedural justice: participation, neutrality, dignity/respect, and trustworthy motives.SEARCH STRATEGYStudies were identified using six electronic databases (CSA, Informit, Ingenta Connect, Ovid, Proquest and Web of Knowledge) and two library catalogues (National Police Library and the Cambridge University Library and dependent libraries). We also searched the reference list of each eligible study, and reviewed the biographies and publication lists of influential authors in the field of procedural justice and police legitimacy, to determine if there were any relevant studies not retrieved in the original search.SELECTION CRITERIAStudies were included if they described any type of public police intervention (e.g. routine patrols, traffic stops, community policing, reassurance policing, problem‐oriented policing, conferencing) that either explicitly stated that the intervention was aimed at improving police legitimacy (through either a directive, training or organizational innovation) or explicitly used at least one of the principles of procedural justice. Studies had to include at least one direct outcome, such as citizen compliance, cooperation, or satisfaction with police, aimed at improving legitimacy, and could also include indirect outcomes, such as reduction in reoffending, or crime and social disorder. We included only studies that evaluated interventions if they were led by public police from any level of government (i.e., local, state and federal law enforcement officers). To be included in the systematic review, studies must have used one of the following research designs: an experimental (randomized) design involving at least two conditions, with one condition being the intervention and the other a control condition; a quasi‐experimental (non‐randomized) design involving at least two conditions, with one condition being the intervention and the other a comparison condition; a quasi‐experimental interrupted time‐series design that involved measurement of an aggregate outcome, such as crime rate, in equally spaced time intervals prior to and following the initiation of the police‐led intervention.DATA COLLECTION AND ANALYSISThe systematic search identified 963 unique studies on police legitimacy and/or procedural justice and policing, of which 933 were obtained. Of those, 163 studies reported on police‐led interventions. A final set of 30 studies, containing 41 independent evaluations, was eligible for meta‐analysis. Data analysis was conducted using Comprehensive Meta‐Analysis 2.0 (CMA), a statistical meta‐analysis software package. We conducted separate meta‐analyses using random effects models for each outcome of policing interventions that had been measured by at least two evaluations. The outcomes analyzed were: Direct – legitimacy, procedural justice, cooperation/compliance, and satisfaction/confidence; Indirect – revictimization or reoffending. We obtained or calculated a single effect size per study per outcome, either a standardized mean difference (g) for a continuous outcome, or an odds ratios for outcomes reported as dichotomous.We also explored possible moderators of policing legitimacy including intervention type, research design, respondent type, crime type, year of publication, and country of publication, using analogs to the ANOVA implemented via subgroup analyses in CMA. In addition, we conducted a series of sensitivity analyses to test the robustness of the results to the following: inclusion of studies where data was imputed, inclusion of poor quality studies (e.g. lack of treatment integrity), and we inspected possible sources of bias in the data, including publication bias and small‐study effects.RESULTSThere were 41 independent evaluations available for meta‐analysis: 7 assessed legitimacy as an outcome, 14 assessed procedural justice, 8 assessed compliance/cooperation, 29 assessed satisfaction/confidence, and 26 assessed reoffending. The direct outcome satisfaction/confidence showed the highest overall effect that was statistically significant (OR 1.75, 95% confidence limits 1.54, 1.99), followed by compliance/cooperation (OR 1.62, 95% confidence limits 1.13, 2.32), and procedural justice (OR 1.47, 95% confidence limits 1.16, 1.86). The estimated effect size for the direct outcome legitimacy (OR 1.58, 95% confidence limits 0.85, 2.95), while quite large, has a wide confidence interval, indicating a high degree of uncertainty around the estimate. Interventions showed a marginal effect on reoffending as an indirect outcome measure (g = ‐0.07, 95% confidence limits ‐0.14, 0.00). When reoffending was broken down by measurement method, studies that measured reoffending using official police data and self‐reported reoffending showed no effect (g = 0.03, 95% confidence limits ‐0.05, 0.11); however, studies that measured self‐reported victimization showed a large decrease in revictimization as a result of the interventions (g = ‐0.13, 95% confidence limits ‐0.23, ‐0.05).AUTHORS' CONCLUSIONSThe main finding of this review is that the effects of legitimacy policing interventions on each direct outcome measure are in a positive direction. For all but the legitimacy outcome, the results were statistically significant. We note that there is a clear lack of randomized experiments in the international research literature that specifically seek to isolate and test the component parts of a legitimacy policing intervention. Notwithstanding the variability in the mode in which legitimacy policing is delivered (i.e., the study intervention) and the complexities around measurement of legitimacy outcomes, our review shows that the dialogue component of front‐line police‐led interventions is important for promoting citizen satisfaction, confidence, compliance and cooperation with the police, and for enhancing perceptions of procedural justice. In practical terms, this means that police can achieve positive changes in citizen attitudes to police through adopting procedurally justice dialogue as a component part of any type of police intervention. We conclude that the type of police intervention (the vehicle for delivering a procedurally just encounter) is secondary to the procedurally just dialogue that underpins the intervention.Plain Language SummaryPolice require voluntary cooperation from the general public to be effective in controlling crime and maintaining order. Research shows that citizens are more likely to cooperate with the police and obey the law when they view the police's authority as legitimate. One way that the police can increase their legitimacy and gain cooperation and respect from citizens is by using “procedurally just” dialogue that adopts language that treats citizens with dignity and respect, conveys trustworthy motives, allows citizens to speak up and express their views during encounters, and by not “profiling” people based on race, gender or any other characteristic. The objective of our review was to systematically assess the direct and indirect benefits of interventions led by the public police that contained elements of this type of procedurally just dialogue. The systematic search found 163 studies that reported on police‐led interventions, and a final set of 30 studies contained data suitable for meta‐analysis. The direct outcomes analyzed were legitimacy, procedural justice, and citizen cooperation/compliance and satisfaction/confidence in the police. In addition, an indirect outcome, reoffending, was also analyzed. The main finding of this review is that police interventions that comprised dialogue with a procedural justice component (or stated specifically that the intervention sought to increase legitimacy) did indeed enhance citizens' views on the legitimacy of the police, with all direct outcomes apart from legitimacy itself being statistically significant. Our review shows that by police adopting procedurally just dialogue, they can use a variety of interventions to enhance legitimacy, reduce reoffending, and promote citizen satisfaction, confidence, compliance and cooperation with the police.