The process-based model of police legitimacy suggests, when police are perceived to make fair decisions and treat people with respect, they will be viewed as legitimate authorities. A randomized controlled trial was used to test the impact of a procedural justice policing intervention, relative to routine police behavior, during traffic stops for excessive speeding in Adana, Turkey.
Drivers stopped by traffic officers for speeding violations were randomly assigned to treatment and control groups. Subjects in the treatment group received the procedural justice policing intervention during traffic stops, while subjects in the control group experienced business-as-usual traffic stops. Treatment officer behavior was guided by a script that helped to ensure that key components of a procedurally-just encounter were delivered. After completion of the traffic stop, drivers were interviewed on the encounter and general perceptions of traffic police.
The experimental analyses show that the infusion of procedural justice principles into police traffic stops does improve citizens’ perceptions of the specific encounter relative to routine police traffic stops. However, the procedural justice treatment did not generate a robust improvement in citizens’ general perceptions of traffic officers.
These results indicate it might be overly optimistic to suggest a single positive encounter can exert a strong influence on durable citizen perceptions of confidence and trust in the police. In addition to ensuring procedurally-just encounters, police executives and police makers should also pay attention to other relevant performance dimensions such as crime control effectiveness, distributive fairness, and lawfulness to change global perceptions of the police.
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A recently-completed systematic review of randomized experiments in policing identified 63 such studies competed between 1970 and 2011 (Braga et al. 2014). All 63 policing randomized experiments were completed in the United States (47, 74.6 %), United Kingdom (11, 17.5 %), Australia (4, 6.3 %) and Canada (1, 1.6 %). The Evidence-Based Policing Matrix (Lum et al. 2011) maintained by George Mason University’s Center for Evidence-Based Crime Policy also does not identify any other randomized field experiments completed in non-Western countries between 2012 and 2014. We are also unaware of any new policing randomized experiments completed in any non-Western countries since the completion of the Braga et al. (2014) systematic review.
Schuck and Rosenbaum (2011) present the preliminary results of a randomized experiment testing the impacts of a Chicago Police Department recruit training program aimed at improving the quality of interpersonal encounters between officers and residents. Preliminary results suggest that recruits who received training displayed more positive procedural-justice attitudes, greater conflict-resolutions skills, and more empathy than did non-trained recruits. Their report did not mention any measurement of changes in citizen perceptions of encounters with treatment and control recruits, however.
While not randomized experiments, the basic propositions of the process-based model of police legitimacy have been tested in non-Western countries such as China (Hu et al. 2015), Israel (Jonathan-Zamir and Weisburd 2013), Jamaica (Reisig and Lloyd 2009), Slovenia (Reisig et al. 2014), and Trinidad and Tobago (Kochel et al. 2013).
The treatment and control traffic officers did not differ significantly in terms of age (Mean = 40.9), years on the job (Mean = 17.8), education (all but one control officer had more than a high school education), and place of birth (roughly one-third of each group were born in Adana with the remainder coming from other areas of Turkey). The control group did have two female officers while the treatment group was comprised completely of male officers. Researchers did not note any substantive differences in the way male and female control officers interacted with stopped motorists.
The final interview instrument did not contain an item that directly measured citizen compliance. The QCET compliance measures were tested for possible inclusion in the Adana RCT during a pilot speed control operation. Unfortunately, respondents provided nearly uniform responses during the pilot. The Adana RCT research team suspected that subjects may have been fearful of encountering legal consequences if reporting non-compliance immediately after the traffic stop. Therefore, a compliance measure was not included in the final instrument used during the actual RCT.
This randomization protocol bears some resemblance to the method used in the Minneapolis Domestic Violence Experiment that was well known to be subverted by some of the participating officers (Sherman and Berk 1984). In this randomized experiment, however, the presence of researchers during all speed control operations, coupled with the follow-up review by commanding officers, seemed to provide adequate safeguards against subversion of the randomization procedure. No violations of randomization protocols were noted during the implementation of the experiment.
Please see Sahin (2014) for statistical comparisons of individuals who refused to participate relative to those who did participate as well as comparisons of RCT participants to the resident populations of Adana. In both sets of comparisons, no substantive differences were noted.
In criminology, experimental research involving the administration of surveys to subjects generally shows response rates ranging from 60 to 70 % (Antrobus et al. 2013 drawing on randomized experiments in Lum et al. 2011). The QCET experiment reported a much lower 13.1 % overall response rate (2746 valid responses out of 20,985 surveys distributed to drivers; Mazerolle et al. 2013). In ScotCET, the overall response rate was only 6.6 % (816 responses returned out of 12,431 surveys distributed to drivers; MacQueen and Bradford 2015). However, subsequent analyses using Cochrane and Elffers methods to explore non-response bias found that the QCET results were robust to any biases associated with low response rates across the treatment and control groups (Antrobus et al. 2013). For a two-tailed α = 0.05 test, the statistical power of the Adana randomized experiment to detect a small effect size (ES = 0.20) was 0.682 and, for both medium and large effect sizes, statistical power exceeded 0.999 (Lipsey 1990).
Although the full model results are not shown, in both the robust and median regression models, gender was not significantly correlated with encounter perceptions. This contradicts the result reported in Table 2.
In the first step, a probit regression model was estimated using regressors which had the least amount of missing data, several of which were obtained from driving records. The resulting model was estimated using 686 of the original 702 drivers invited to participate in the study. The regressors included the treatment assignment dummy (b = 0.70; s.e. = 0.11), the raw number of demerits (b = –0.02; s.e. = 0.01) and its square (b × 100 = 0.06; s.e. × 100 = 0.03), a dummy for male (b = 0.23; s.e. = 0.22), a dummy for excessive speeding (b = 0.17; s.e. = 0.13), a dummy for having been born in Adana (b = 0.49; s.e. = 0.32), order of study entry (b = 0.06; s.e. = 0.03), and the interaction between the dummies for gender and birthplace (b = –0.56; s.e. = 0.34). It should be noted that the coefficients corresponding to the inverse Mills ratio are positive but not statistically significant in either of the substantive equations. Therefore, while there is evidence of positive selection (i.e., the unobservables that make a person more likely to participate in the survey also give him or her more favorable procedural justice perceptions), it is not substantial and does not appear to badly bias the reported results.
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Appendix 1: Procedural Justice Script
Good morning/afternoon sir/madam. My name is officer_________
Do you know how we conduct our speed control operations?
Let me provide you some brief information about speed controls.
It is one of the most well-enforced traffic controls in Turkey.
The radar equipment in our patrol car accurately records the car’s speed
We give tickets to all drivers who pass the speed limit we stop for speeding regardless of their socioeconomic and occupational position.
Our aim is to reduce traffic accidents
Do you know that approximately 30 percent of traffic accidents in Turkey are related to speeding?
In Adana alone there were 55 deaths and 5371 injuries in 2011 related to traffic accidents.
Guess how difficult for us to tell a person that his/her loved one has died or has been seriously injured.
You can help us reduce these accidents by continually driving carefully and responsibly.
Do you think we should continue conducting speed controls?
Today, you have been stopped because our radar equipped patrol car detected that your speed was ___________. This speed is clearly above the stated limit of 70 km/h.
Now, may I have your documents please?
Thank you. I wish you a safe trip. Please be careful next time. Thank you for your cooperation.
See Table 5.
See Fig. 3.
See Fig. 4.
See Fig. 5.
See Table 6.
See Table 7.
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Sahin, N., Braga, A.A., Apel, R. et al. The Impact of Procedurally-Just Policing on Citizen Perceptions of Police During Traffic Stops: The Adana Randomized Controlled Trial. J Quant Criminol 33, 701–726 (2017). https://doi.org/10.1007/s10940-016-9308-7
- Procedural justice
- Traffic stops
- Randomized experiment