Evidence-Based Policing Matrix

HomeEvidence-Based PolicingThe MatrixResearch on Micro-PlacesMicro Places – Groff et al. (2015) (Offender Focused)

Micro Places – Groff et al. (2015) (Offender Focused)

Study Reference:

Groff, E. R., Ratcliffe, J. H., Haberman, C. P., Sorg, E. T., Joyce, N. M., Taylor, R. B. (2015). Does what police do at hot spots matter? The Philadelphia Policing Tactics Experiment. Criminology, 53(1), 23-53.


Location in the Matrix; Methodological Rigor; Outcome:

Micro places; Focused; Proactive; Very Rigorous; Effective


What police practice or strategy was examined?

This study examined three different approaches to hot spots policing – foot patrol, problem-solving, and offender-focused strategies. Hence, this study is reported three times in the Matrix, and the focus for this summary is the offender-focused policing approach. This approach consisted of identifying repeat violent offenders who either lived in or were suspected of being involved in violent crimes in the target areas and focusing extra attention on them. Offenders qualified for the initiative if they had a history of violent offenses and criminal intelligence suggested they were involved in a criminal lifestyle. Dedicated teams of officers drawn from the districts’ tactical operations squads and an intelligence analyst identified and maintained a list of individuals thought to be causing the problems in the hot spot deployment areas. The offender-focused team members and patrol officers made frequent contact with these prolific offenders ranging from making small talk with a known offender to serving arrest warrants for a recently committed offense. The most frequent tactic used was surveillance followed by aggressive patrol and the formation of partnerships with beat officers. Overall, each tactic ran for a minimum of 12 weeks and a maximum of 24 weeks at any single target area.


How was the intervention evaluated?

A total of 81 high crime areas were identified for the overall study. 27 of these areas were selected as amenable for each condition (thus, there were 27 areas selected for the offender-focused portion of this study). Of these 27 areas, 20 areas were randomly assigned to receive offender-focused strategies and 7 acted as control sites that received usual police services. The researchers examined two separate violent crime outcome measures: all violent crime and violent street felonies, both taken from the Philadelphia Police Department’s crime incident database.


What were the key findings?

Offender-focused policing significantly reduced expected all violent crime counts by roughly 42% relative to the control areas. A significant treatment effect also occurred for offender-focused policing on violent felony counts; the expected violent felony counts in the treatment areas were approximately 50% lower than the expected violent felony counts observed in the seven controls areas during implementation.


What were the implications for law enforcement?

The success of this tactic has several possible practical explanations. Treatment sites had a clear mission and a dedicated team of highly motivated officers who were exempt from answering calls for service and were supported by an intelligence analyst. Once the dedicated intelligence officer identified a list of offenders, the teams of officers selected from the districts’ tactical squads could use their existing skill set with little additional training. Officer surveys showed they supported the notion of focusing on repeat violent offenders.


Where can I find more information about this intervention, similar types of intervention, or related studies?