Evidence-Based Research Projects

Evidence-based research, and more specifically, “evidence-based policing” is a term coined by Sherman in 1998, “is the use of the best available research on the outcomes of police work to implement guidelines and evaluate agencies, units, and officers.” Sherman stressed the importance of creating knowledge through experimental research in which the research is based in theory and examines different strategies and/or solutions that improve current practices. The following are evidence-based research projects that have been conducted by members of the Center.

A Blind Randomized Controlled Trial to Test Tactical Police Responses to Micro-Time Hot Spots for Residential Burglaries and Thefts from Vehicles

A micro-time hot spot, also called a "crime pattern" in crime analysis practice, is the emergence of several closely-related crimes within a few minutes travel distance from one another (i.e., micro-place) that occurs within one to two weeks (i.e., micro-time)—a crime “flare up.”  Once a micro-time hot spot appears, it can last for several weeks or months before running its course, cooling down, and ending on its own. The concept of the flare up is routed in the near repeat phenomenon as it is a spatial cluster of near repeats occurring over a relatively short period of time. In this study, the partially blocked random controlled trial, was conducted by Dr. Rachel Santos (external research partner) and Dr. Roberto Santos (police commander and internal project director) with the Port St. Lucie (FL) Police Department "pro bono,” and only the chief, assistant chiefs, and crime analysts were aware that the experiment was taking place. 

The study tested the effectiveness of directed patrol deployed in micro-time hot spots over several weeks, which included patrolling areas in vehicles making subject and vehicle stops as well as contacting citizens with crime prevention information. The goal of the response was to prevent crime from continuing in the micro-time hot spot and causing it to “cool down” sooner than it would without response. The research occurred within the context of the agency's everyday crime reduction efforts, so is a test of realistic police practice. That is, the police department had identified and responded to micro-time hot spots systematically for many years. For this study, as crime analysts identified micro-time hot spots on a daily basis, the micro-time hot spots were randomly assigned for response "on the fly." Those not selected for response were not disseminated so that the police personnel had no knowledge they had occurred. A previously established system of response and accountability in the agency ensured consistent and thorough responses throughout the 2-year treatment period. Preliminary findings of crime that occurred after 15, 30, 60, and 90 days show that the response was effective. The following is the peer-reviewed publication resulting from the research.

Santos, R. B., & Santos, R. G. (2020). Proactive police response in property crime micro-time hot spots: Results from a partially-blocked blind random controlled trial. Journal of Quantitative Criminology, 1-21. DOI 10.1007/s10940-020-09456-8.

Abstract: Objectives: To evaluate the impact of proactive police response on residential burglary and theft from vehicle in micro-time hot spots as well as whether spatial displacement occurs. Methods: Over 2 years, 114 treatment and 103 control micro-time hot spots were assigned to groups using “trickle-flow” randomization. Responses were implemented as part of the police department’s established practices, and micro-time hot spots were blocked based on their temporal proximity—sprees or ongoing. The study was blinded and tested proactive patrol versus a no-dosage control condition. Results: The department responded to each micro-time hot spot with, on average, five 20-min responses per day for 19 days. Eighty percent of the response time involved conducting directed patrol without encountering suspicious activity. Results show that treatment micro-time hot spots had significantly fewer crimes after 15 days (79%) and 30 days (74%). Treatment effects were greatest in the first 15 days (1.15) followed by days 16–30 (.83). Conclusions: The study examines a real-world strategy institutionalized into the day-today operations of a police department. The largest impact on crime was seen during response. In addition, crime reductions that occurred while micro-time hot spots received response held for 2 months after the responses end with no evidence of spatial displacement. Our findings reveal larger effect sizes than most hot spots policing studies which may be due to how the unit of analysis was defined, the systematic nature of the response implementation, and the use of a no-dosage, blind control condition.

A Partially Blocked Randomized Controlled Trial of Offender-Focused Police Intervention in Residential Burglary and Theft from Vehicle Hot Spots

Funded by the Bureau of Justice Assistance, Dr. Rachel Santos partnered with the Port St. Lucie, FL Police Department and Dr. Roberto Santos (police commander and internal project director) to conduct a partially-blocked random controlled trial testing the effects of an offender-based intervention in property crime hot spots.  The following are peer-reviewed publications resulting from the research.

Santos, R.B., & Santos, R.G. (2016). Offender-focused police strategies in residential burglary and theft from vehicle hot spots: A partially blocked randomized controlled trial. Journal of Experimental Criminology, 12(3), 373–402.

Abstract: To test an offender-focused police intervention in residential burglary and residential theft from vehicle hot spots and its effect on crime, arrests, and offender recidivism. The intervention was prevention-focused, in which detectives contacted offenders and their families at their homes to discourage criminal activity. The study was a partially blocked, randomized controlled field experiment in 24 treatment and 24 control hot spots in one suburban city with average crime levels. Negative binomial and ordinary least squares (OLS) regression were used to test the effect of the presence of intervention and its dosage on crime and offender recidivism, and examination of average and standardized treatment effects were conducted. The analyses of the hot spot impact measures did not reveal significant results to indicate that the treatment had an effect on crime or arrest counts, or on repeat arrests of the targeted or non-targeted offenders living in the hot spots. However, the relationships, while not significant, were in a promising direction. The collective findings from all four impact measures suggest that the intervention may have had some influence on the targeted offenders, as well as in the treatment hot spots. So, while the experimental results did not show an impact, they are promising. Limitations include large hot spots, the low case number, low base rates, and inadequate impact measures. Suggestions are provided for police agencies and researchers for implementing preventive offender-focused strategies and conducting studies in suburban cities.

Santos, R.G. (2018). Offender and family member perceptions after an offender-focused hot spots policing strategy.  Policing: An International Journal, 41(3), 386-400.

Abstract: This article examines how both offenders and their families perceived their interactions with police and whether there were negative consequences of the offender-focused strategy that was implemented in a hot spots policing experiment. Data from interviews of 32 offenders and 29 family members are examined qualitatively for themes to evaluate how the strategy was carried out and how it impacted offenders’ behavior and both groups’ perceptions of the police detectives and the strategy overall. The results show that there was overwhelming agreement by both offenders and their family members that the police detectives who contacted them treated both groups with dignity and respect. After the contact was over, the offenders appeared to commit less crime, followed probation more closely, and had positive feelings about what the police detectives were trying to do. Improvement of the offenders’ relationships with their families was an unanticipated finding indicating a diffusion of benefits of the strategy. The results suggest that when procedural justice principles are used in an offender-focused police intervention, positive impact can be achieved without negative consequences. This is a rare example of an in-depth evaluation of the perceptions of offenders and family members contacted through a hot spots policing offender-focused strategy.

Quasi-Experimental Test of Tactical Police Responses to Micro-Time Hot Spots for Residential Burglaries and Thefts from Vehicles

Through a quasi-experimental design this study tested the effectiveness of directed patrol deployed in micro-time hot spots responded to by a police department over five years. The following are peer-reviewed publications resulting from the research. The National Institute of Justice has recently published a review of Santos’ research in which they established that based on these results, police response to micro-time hot spots is effective.

Santos, R.G. & Santos, R.B. (2015). An ex post facto evaluation of tactical police response in residential theft from vehicle micro-time hot spots. Journal of Quantitative Criminology, 31(4), 679-698.

Abstract: To evaluate with an ex post facto quasi-experimental design the impact of tactical police response on residential theft from vehicle crime in micro-time hot spots as well as whether spatial displacement occurs. The evaluation uses 5 years of data from one police agency that responded to micro-time hot spots as part of its normal crime reduction efforts. To determine the experimental comparison group, propensity scores were computed using logistic regression. Cases were matched using greedy 1–1 matching with a caliper of 0.10 of the standard deviation of the logit of the propensity score and resulted in 86 pairs. t Tests were used to examine the effect of the treatment and whether spatial displacement of crime occurred as a result. Results showed that when police responded with about seven responses per day and for between 2 and 3 weeks, there was nearly a 20 % reduction in residential theft from vehicle crimes, and the micro-time hot spots with response did not last as long as those that did not. Results also showed no spatial displacement of crime as a result of the response. This evaluation is first to examine tactical police strategies for property crimes occurring at micro-places in micro-time. Findings support the hypothesis that micro-time hot spots are less severe and ‘‘cool off’’ more quickly after a response. Thus, police should consider responding to property crime occurring in micro-places at a smaller temporal unit. Future research should further explore this unit of police response to corroborate these results.

Santos, R.G., & Santos, R.B. (2015). Practice-based research: Ex post facto evaluation of evidence-based police practices implemented in residential burglary micro-time hot spots. Evaluation Review, 39(5), 451-479.

Abstract: Police agencies around the country are implementing various strategies to reduce crime in their communities that need to be evaluated. These strategies are often based on systematic crime analysis and are focused on crime occurring in hot spots, which are areas of disproportionate amounts of crime. This article takes a practice-based research approach to evaluate whether evidence-based police strategies implemented by one police agency as its normal everyday crime reduction practice are effective in reducing residential burglary incidents in micro-time hot spots. A quasi-experimental ex post facto design is employed using 5 years of data from one police agency that has institutionalized the identification and response to micro-time hot spots into its day-to-day practices. Propensity score matching is used to match 54 pairs of micro-time hot spots using logistic regression to compute the propensity scores and greedy 1 to 1 matching with a caliper width of 0.5 of the standard deviation of the logit to match the cases. Independent t-tests show that tactical police response to micro-time hot spots can lead to significant reductions in residential burglary incidents without the spatial displacement of crime. Tactical police responses that seek to achieve short-term reductions in crime appear to be well suited for micro-time hot spots since they are, by nature, short term. Importantly, the conclusions are based on the evaluation of an agency’s systematic implementation of the evidence-based practices as its normal practices and not for the sake of research.

Santos, R.B., & Santos, R.G. (2015).  Examination of police dosage in residential burglary and theft from vehicle micro-time hots spots.  Crime Science, 4(27), 1-12.  

Abstract: Rooted in the near repeat phenomenon and police crime analysis, a crime “flare up” or micro-time hot spot is the emergence of several closely-related crimes within a few minutes’ travel distance from one another. It occurs within 1–2 weeks and can last several weeks or months before running its course and cooling down. A micro-time hot spot is a type of crime pattern identified by police crime analysts to guide short-term police response, particularly directed patrol. Published work by these authors has examined a subset of the 5 years of data to test the effectiveness of the Port St. Lucie, FL Police Department’s response to micro-time hot spots. Those quasi-experimental studies found separately for burglary and theft from vehicle occurring in residential areas that micro-time hot spots receiving police response had nearly 20 % fewer  subsequent crimes than those receiving no police response. This study examines all 121 residential burglary and 163 residential theft from vehicle micro-time hot spots receiving police response to understand how two factors of police response dosage (i.e., the amount of directed patrol and how quickly directed patrol is deployed) are related to the amount of subsequent crime. Separate negative binominal analyses for each crime type showed that more directed patrols per day were related to lower levels of subsequent crime for both crime types, and a quicker response was related to lower crime for residential theft from vehicle. That is, the more and quicker the response, the quicker resolution and cooling off of the micro-time hot spot. The findings were stronger for residential burglary, and a visual examination of first standard deviation confident intervals of directed patrol rate by crime suggests that between four and six directed patrols per day in residential burglary micro-time hot spots was optimal. Although the data are from one police agency, these promising results support future research and provide guidance to police for implementing directed patrol in short-term hot spots of property crime.

Integrating Crime Analysis into Patrol Work within a Community Policing Context

With funding from the Office of Community-Oriented Policing Services, Dr. Rachel Santos partnered with Police Executive Research Forum (PERF) to assess the role of crime analysis within the patrol function at a national level and make recommendations for police practice.  The project included 1) a national police department survey of patrol commanders and crime analysts on crime analysis and crime reduction, 2) focus groups of police personnel at various levels (i.e., officers, supervisors, managers, executive, and crime analysts), 3) three in depth site visits of police agencies. The following are peer-reviewed publications resulting from the research.

Smith, J., Santos, R.B., & Santos, R.G. (2018). Evidence-based policing and the stratified integration of crime analysis in police agencies: National survey results. Policing: A Journal of Policy and Practice, 12 (3), 303–315.

Abstract: Using data collected from a 2008 national survey of over 1,000 agencies, this paper presents findings about the stratified integration of crime analysis into police patrol operations. Relationships are examined among stratified crime analysis integration, and the agency’s commitment to crime analysis, evidence-based crime reduction approaches, and accountability mechanisms. The analysis shows that there is no connection between patrol commanders’ commitment to crime analysis or prioritization of evidence-based practices and the appropriate use of crime analysis by line-level officers, first-line supervisors, and managers (i.e., stratified crime analysis integration). The analysis does show that having a designated crime analyst and prioritizing accountability for crime reduction at all ranks were strong  predictors of stratified crime analysis integration. The findings suggest that the presence of a primary analyst and of accountability mechanisms is more than agencies simply ‘saying’ that evidence-based practices or crime analysis is important.

Santos, R.B., & Taylor, B. (2014). The integration of crime analysis into police patrol work: results from a national survey of law enforcement. Policing: An International Journal of Police Strategies and Management, 37(3), 501-520.

Abstract: The purpose of this paper is to examine national survey data of police agencies in the USA to explore the current state of crime analysis integration to patrol crime reduction work. The data examined in this paper are from a national quantitative survey which sought to understand how crime analysis results are used by officers as well as higher ranking personnel in the patrol division and what types of strategies are implemented using crime analysis. The findings show that the routine use of crime analysis is not well integrated. Despite the low integration, however, some differenceswere found.Management uses crime analysis themost overall, but officers and first-line supervisors use tactical crime analysis more routinely than management, where management personnel use evaluation most routinely. Tactical crime analysis is used most often for directed patrol, strategic for both directed patrol and general information, and evaluation for both general information and crime prevention. Analysis of using analysis proactively shows that agencies use tactical crime analysis most proactively, followed by the strategic crime analysis, then evaluation. The study relies on self-report surveys, so the results may suffer from some of the general limitations of self-reports. Also, the study resulted in a lower response rate than surveys of police agencies typically achieve. Although responding and non-responding agencies were comparable in terms of population size, number of officers, and region of the country,the response rate was about 55 percent. However, it is a possibility based on the analysis results that non-responses may reflect a disinterest in the topic or the lack of integration of crime analysis. This is the first national survey that focussed specifically on crime analysis integration in patrol work for crime reduction. The value of the results presented here are in the description of the current state of crime analysis integration in the USA which has not been investigated in such depth before and the identifications of gaps in both research in practice.

Taylor, B. & Boba, R. (2011). Guidebook for integrating crime analysis into patrol within a community policing context [PDF]. Washington DC: Office of Community Oriented Policing Services.