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5 examples of how evidence-based policing enhances law enforcement

Proactive policing that targets hot places, hot people and hot times based on knowledge gleaned from crime analysts is an effective crime-reduction strategy


The challenge is overcoming the belief by some that officers who participate in evidence-based policing desire to study problems incessantly or have a “paralysis by analysis” mindset.


Successful day-to-day policing is largely based on building relationships and trust both internally in our organizations and externally in our communities – emotional concepts that are often difficult to measure.

Getting a confession from a subject, making connections with a shop owner or community member, or a patrol officer using natural, keen instincts to read cues that a subject needs further investigation, are examples of successful policing that are often considered the “art and craft” of law enforcement.

However, that doesn’t mean we should ignore the contextual data, technology and best available empirical research to train our officers and inform their activity. [1] This practice of evidence-based policing is a decision-making perspective that suggests policies and practices should be supported by assessing and analyzing data, rigorous scientific evidence about what works and what does not, and acknowledging that research should be part of the conversation around police operations. [2-4]

There is still a great deal of weight placed on the craft or art of policing, and there should be. Most every police department has a police officer who is a magnet for guns, stolen cars, wanted subjects and those carrying large amounts of illegal narcotics. Still, relying on the craft of policing and random patrol can only take us so far. What if we could enhance these instincts with the best available evidence – data that rules out other theories and then informs and challenges policies, practices and decisions by continually assessing the information gathered?

Evidence shows that proactive policing that targets hot places, hot people and hot times based on knowledge gleaned from crime analysts has proved to be an effective crime-reduction strategy. [5] If we can couple instinctive proactive policing while addressing hot spots and reducing criminal opportunities through deterrence then the police might be able to exert their influence in meaningful ways.

The challenge is overcoming the belief by some that officers who participate in evidence-based policing desire to study problems incessantly or have a “paralysis by analysis” mindset. [3] Members of the American Society of Evidence-Based Policing are out to change that perception. The society is comprised of front-line cops who suggest police become the drivers of research while partnering with researchers to find the answers to questions that are relevant to policing’s core missions. What is critically important is that as police officers, we are the ones who have the most accurate view of the world within which we operate.


The following examples of evidence-based policing show promising results that might be applicable in your jurisdictions. The research is based on rigorous evaluation often done with randomized controlled trials (RCTs), considered the gold standard in scientific methodology. [4-6] RCTs are methodology designs used to compare the counterfactual (what would have happened at the same time as the intervention) but were not discovered because something else was done. They are essentially randomized comparisons of an equal number of treatments (interventions) compared to the business as usual (controls). [5]

1. Repeat offenders and crime variations

Evidence: Crime risks vary consistently and are typically concentrated by the time of day, the day of the week, season, type of holiday and even weather conditions. Additionally, only a few offenders commit most of the crime. Some estimates show that just 3-5 percent of the population commit 50-60 percent of crime. Additionally, based on the “power few” or loosely connected 20/80 rule, 80 percent of all crime might be committed by 20 percent of the population.

Recommendation: With the assistance of a crime analyst, track repeat offenders for repeat offenses and monitor when they are in and out of jail. Staff your patrol teams when crime is the highest. Also, after assessing the data, use crime reduction teams to target hot places, hot people and hot times. Avoid random patrol and consider a focused offender approach – partner with probation, parole and prosecution.

Some police ignore their own crime data of where and when crime is occurring and tend to overstaff during off times and days – more than likely due to labor/union contractual expectations. [4]

For crime to generally happen there must be a likely offender, a suitable target and the absence of a capable guardian or someone to care enough to observe or intervene.

2. Hot spot policing

Evidence: If police assessed the data and patrolled hot places sporadically and unpredictably every two hours for 10-16 minutes they could have a measurable impact on crime with a policing strategy known as the “Koper Curve.”

In Sacramento, a hot spot study was conducted involving an intervention area (the hot spot patrols), which was then compared to a control area or (business was usual). The result: Part I Crime incidents decreased 25 percent in the intervention (treatment) hot spots compared to the business as usual (control) hot spots (where crime incidents rose 27 percent). Calls for service declined by about 8 percent in the intervention group and increased by approximately 11 percent in the business-as-usual hot spots.

Recommendation: Consider conducting traffic and pedestrian stops proactively in locations with violent activity. As a police leader, visit these hot spots frequently to demonstrate commitment, enthusiasm, credibility and an overall investment in the plan. Further, by visiting, you may gain additional insights into new strategies and deployments. [5]

Putting a “cop on the dot” in an area where crime takes place is probably not very realistic for most resource-strapped police departments running from call to call. However, if police leaders can place an officer in that hot spot for 15 minutes unpredictably and sporadically, then research shows a decrease in crime that lasts for 2 hours. Suddenly, this becomes much more realistic and manageable.

3. Burglary risks

Evidence: Predictable risk of residential burglary occurs in the areas to the side, front and behind the victim’s residence for the first 10-14 days after the crime. This evidence has been ignored for years and was just recently tested in Redlands, California, and Baltimore City, Maryland.

Recommendation: After a burglary warn neighbors of their risk and suggest ways in which they can target harden their residence such as locking back windows; utilizing ring technology, video surveillance, alarms and motion lights; cutting away shrubbery; and encouraging more guardianship of neighbors.

4. Domestic homicide predictors

Evidence: Previous suicide attempts appear to be the best predictor of domestic homicide.

Thames Valley Police (UK) records were examined for 118 victims and 120 offenders in 118 cases of “deadly” domestic violence: murder, attempted murder, manslaughter and grievous bodily harm. The case-control study found male offenders who committed serious domestic assaults were over three times more likely than other violent offenders to have had markers of suicidal tendencies. [7]

Recommendation: Use this information as a threat matrix and tailor services accordingly. If there are those suicidal tendencies, utilize support services and other partners for prevention.

5. Cognitive interviewing techniques

Evidence: According to several studies, cognitive interviewing techniques, or asking open-ended questions, reinstating the context by eliciting memory retrieval cues, and focusing on sensory details – resulted in 25-40 percent more details.

Many U.S. local police do not practice cognitive interviewing techniques when speaking to victims and witnesses of violent crime, despite significant evidence that shows the victim will feel heard, empowered, and less often felt re-victimized.

Recommendation: Show empathy – acknowledge trauma and pain, use open-ended questions, i.e., “tell me more” and “help me understand.” Use powerful retrieval cues like smell and sound. Ask impact questions – “How has this impacted you? What can’t you forget about the experience?”


Dynamic demands in daily policing require shifting priorities while allowing officers to make sound decisions rooted in discretion. [1] Evidence-based policing doesn’t suggest replacing the craft of policing – it advocates for enhancing it. [4]

It is my experience that police generally welcome research and data if they are empowered, included and the measurements explained to them in concise ways. However, it is these measurements that researchers and practitioners are often at odds with – crime reduction versus crime detection or how evaluations are done – experiments, quasi-experiments and before/after analysis. [2]

Police supervisors and managers must continue to translate and digest the research in ways that make sense to our front-line police but look and feel like everyday police activities, while encouraging officers to participate in their own officer-led research. [2]

Finally, we don’t prove anything in science; we only test theories that might work in one jurisdiction but might be less successful in another. [8,9] The hope is that we progress to the point where one day we will consistently assess our data with competent crime analysts and place our officers in positions to succeed, both from an officer-safety and a crime-reduction perspective, for themselves, their departments and the communities they serve. Besides as Neil de Grasse Tyson once said, “To be scientifically literate is to empower yourself to know when someone else is full of shit.”

If you want to learn more about evidence-based policing or how to conduct rapid officer-led research trials with the help of organizations such as BetaGov, register for the third annual ASEBP conference on May 20-21 at the University of Cincinnati. Attendees will even be provided an opportunity to participate in a quasi-experiment on a virtual reality simulator by Street Smarts VR.

To learn more about the American Society of Evidence-Based Policing, visit



1. Potts J. The benefits, challenges, and lessons of evidence-based policing. The Journal of California Law Enforcement. 2017, 51, 2:4.

2. Lum C, Telep CW, Koper CS, Grieco J. Receptivity to research in policing. Justice Research and Policy. 2012, 14(1), 61-95.

3. Sherman LW. A tipping point for “totally evidenced policing” ten ideas for building an evidence-based police agency. International Criminal Justice Review. 2015, 25(1), 11-29.

4. Sherman LW. The rise of evidence-based policing: Targeting, testing, and tracking. Crime and Justice. 2013, 42(1), 377-451.

5. Ratcliffe J. Reducing Crime: A Companion for Police Leaders. Routledge, 2018.

6. Syed M. Black Box Thinking: Why Most People Never Learn from Their Mistakes But Some Do. Penguin, 2015.

7. Sherman L. The Police Foundation Annual Conference. Two cheers for evidence-based policing.

8. Alpert G, Cordner G. Striking a balance – Research, science, and policing. Research in Brief. The Police Chief. 2018, 8:14-15.

9. Greene JR. The upside and downside of the ‘Police Science’ epistemic community. Policing: A Journal of Policy and Practice. 2014, 8(4), 379-392.


Repeat offenders and crime variation

  • Cohn EG. The prediction of police calls for service: The influence of weather and temporal variables on rape and domestic violence. Journal of Environmental Psychology, 1993, 13:71–83.
  • Sherman L. Attacking crime: Police and crime control. In Modern Policing, edited by Michael Tonry and Norval Morris. Vol. 15 of Crime and Justice: A Review of Research, edited by Michael Tonry. Chicago: University of Chicago Press, 1992.
  • Sherman LW, Gartin PR, Buerger ME. Hot spots of predatory crime: routine activities and the criminology of place. Criminology. 1989, 27(1), 27–56.
  • Blumstein A, Cohen J, Roth JA, Nagin D. Criminal Careers and “Career Criminals.” Washington, DC: National Academies Press, 1986.
  • Kock R. 80–20 Principle: The Secret to Success by Achieving More With Less. New York: Doubleday, 1989.
  • Martinez NN, Lee Y, Eck JE, SooHyun O. Ravenous wolves revisited: A systematic review of offending concentration. Crime Science. 2017, 6(1),10.

Hot spot policing

  • Koper CS. Just enough police presence: Reducing crime and disorderly behavior by optimizing patrol time in crime hot spots. Justice Quarterly. 1995, 12:649–72.
  • Police Foundation. 5 Things You Need to Know About Hot Spots Polocing & the “Koper Curve” Theory.
  • Telep CW, Mitchell RJ, Weisburd D. How much time should the police spend at crime hot spots? Answers from a police agency directed randomized field trial in Sacramento, California. Justice Quarterly. 2014, 31, 905-933.
  • Bowers K, Shane J, Pease K. Prospective hot-spotting: The future of crime mapping? British Journal of Criminology. 2004, 44(5): 641–58.

Burglary risks

Domestic homicide predictors

  • Thornton S. Police attempts to predict domestic murder and serious assaults: Is early warning possible yet? Cambridge Journal of Evidence-Based Policing. 2017, 1(2-3), 64-80.

Cognitive interviewing techniques

Jason Potts is Director of the Department of Public Safety director for the City of Las Vegas, which provides the public with law enforcement and detention services. This department manages the city jail and includes the deputy city marshals (who provide public safety at city parks and facilities) and animal protection services.

Director Potts started his policing career with the Vallejo Police Department in Northern California, where he moved up the ranks to captain, leading the Operations Bureau, Investigations Bureau and Emergency Services Unit. Before his career in municipal policing, he worked for U.S. Customs and Border Protection as a border patrol agent.

During his career at the Vallejo Police Department, Potts worked in various capacities, including patrol, crime suppression, investigations, SWAT, field training, internal affairs, the FBI’s Solano County Violent Gang Task Force and the Oakland Drug Enforcement Administration Task Force. He also is a military reserve special agent with the Coast Guard Investigative Service.

Potts earned a master’s degree in Criminology, Law, and Society from the University of California, Irvine. He has a bachelor’s degree in Management from St. Mary’s College in California. He holds a certificate of completion from the Police Executive Research Forum, Senior Management Institute of Police. He is a graduate of the California Peace Officers Standards and Training Command College and is a National Institute of Justice Law Enforcement Advancing Data and Science Program alumni with the U.S. Department of Justice.

An advocate for evidence-based policing, Potts serves on the Executive Board of the American Society of Evidence-Based Policing, is a member of the Council on Criminal Justice (violent crime working group), and is a National Policing Institute fellow. He has been a strong proponent of officer safety and wellness, data-driven patrol deployments, community engagement, practitioner-led research, innovative practices and technology. In June 2019, he was recognized nationally at George Mason University for his collective efforts in advocating and implementing evidence-based policing.