Ideas in American POLICE FOUNDATION Policing July 1998 Evidence-Based Policing By Lawrence W. Sherman Most of us have thought of the statistician’s work as that of measuring Abstract and predicting . but few of us have thought it the statistician’s duty to try to The new paradigm of “evidence-based medicine” holds bring about changes in the things that he important implications for policing. It suggests that just doing [or she] measures. —W. Edwards Deming research is not enough and that proactive efforts are required to push accumulated research evidence into practice through national Ideas in American Policing presents and community guidelines. These guidelines can then focus in- commentary and insight from house evaluations of what works best across agencies, units, leading criminologists on issues of interest to scholars, practitioners, victims, and officers. Statistical adjustments for the risk factors and policymakers. The papers shaping crime can provide fair comparisons across police units, published in this series are from the Police Foundation lecture series of including national rankings of police agencies by their crime the same name. Points of view in prevention effectiveness. The example of domestic violence, for this document are those of the author and do not necessarily which accumulated National Institute of Justice research could represent the official position of the lead to evidence-based guidelines, illustrates the way in which Police Foundation. agency-based outcomes research could further reduce violence ©1998 Police Foundation and Lawrence W. Sherman. All rights reserved. against victims. National pressure to adopt this paradigm could Lawrence W. Sherman is come from agency-ranking studies, but police agency capacity to professor and chair of the adopt it will require new data systems creating “medical charts” Department of Criminology for crime victims, annual audits of crime reporting systems, and and Criminal Justice at the in-house “evidence cops” who document the ongoing patterns University of Maryland at and effects of police practices in light of published and in-house College Park. He was the research. These analyses can then be integrated into the NYPD Police Foundation’s director Compstat feedback model for management accountability and of research from 1979 to continuous quality improvement. 1985. Of all the ideas in policing, million in print (Sackett and Medicine, in fact, seems just one stands out as the most Rosenberg 1995)—as the highly as resistant to the use of evidence powerful force for change: police rigorous scientific evidence used to guide practice as are fields with practices should be based on to guide medical practices. He lower educational requirements, scientific evidence about what has suggested that policing such as policing. The National works best. Early in this century, should therefore be more like Institutes of Health (NIH) Berkeley Police Chief August medicine. Consensus Guidelines are a case Vollmer’s partnership with his Sherman was right about the in point. NIH convenes advisory local university helped generate need for many more randomized boards to issue to physicians this idea (Carte and Carte 1975), experiments in policing, but recommendations that are based which was clearly derived from wrong about how much medicine on intensive reviews of research that era’s expansion of the was really based on scientific evidence on specific medical scientific method into medicine, research. New evidence shows practices. These recommendations management, agriculture, and that doctors resist changing usually receive extensive publicity, many other fields (Cheit 1975). practices based on new research and are reinforced by mailings of While science had greater initial just as much as police do, if not the guideline summaries to some impact in those other professions more so. Closer examination one hundred thousand doctors. during the first half of the reveals medicine to be a But according to a RAND century, policing in recent battleground between research evaluation, doctors rarely change decades has been moving rapidly and practice, with useful lessons their practices in response to to catch up. However, any for policing on new ways to publication of these guidelines assessment of this idea in modern promote research. Those lessons (Kosecoff et al. 1987, as cited in policing must begin with an come from a new strategy called Millenson 1997). Thus three accurate benchmark: catching up “evidence-based medicine,”1 years after research found that to what? More complete evidence “widely hailed as the long-sought heart attack patients treated with on the linkage between research link between research and calcium antagonists were more and practice suggests a new practice” (Zuger 1997) to solve likely to die, doctors still paradigm for police improvement problems like the following prescribed this dangerous drug to and for public safety in general: (Millenson 1997, 4, 122, 131): one-third of heart attack patients. evidence-based crime prevention. Eight years after antibiotics were • An estimated 85 percent of For years, Sherman (1984, shown to cure ulcers, 90 percent medical practices remain 1992) and others have used of ulcer patients remained untested by research evidence. medicine as the exemplar of a untreated by antibiotics profession based upon strong • Most doctors rarely read the (Millenson 1997, 123–25). scientific evidence. Sherman has 2,500 medical journals available, and instead base their praised medicine as a field in Evidence Cops which practitioners have advanced practice on local custom. training in the scientific method • Most studies that do guide The struggle to change and keep up-to-date with the practice use weak, non- medical practice based on most recent research evidence by randomized research designs. research evidence has a long reading medical journals. He has history, with valuable implications cited the large body of for policing. In the 1840s, Ignaz randomized controlled Semmelweiss found evidence that 1 The term “evidence” in this mono- experiments in medicine—now graph refers to scientific, not criminal, maternal death in childbirth estimated to number almost one evidence. could be reduced if doctors ——2—— Increased pressure for “reinventing government” to One way to describe people focus on measurable results is reflected in the 1994 U.S. who try to apply research is the Government Performance Results Act (GPRA), which requires all role of “evidence cop.” federal agencies to file annual reports on quantitative indicators of their achievements. Education is under growing pressure to raise test scores as proof that children washed their hands before Hospital in Los Angeles. As are learning, which has led to delivering babies. He then tried to director of the hospital’s Center increased discussion of research apply this research to medical for Applied Health Services evidence on what works in practice in Vienna, which led to Research, Weingarten is an education (Raspberry 1998). And his being driven out of town by evidence-cop-in-residence. His the U.S. Congress has required his boss, the chief obstetrician. job is to monitor what the 2,250 that the effectiveness of federally Hundreds of thousands of women doctors are doing to patients at funded crime prevention died because the profession the hospital and to detect programs be evaluated using refused to comply with his practices that run counter to “rigorous and scientifically evidence-based guidelines for recommendations based on recognized standards and some forty years. The story shows research evidence. He does this methodologies” (House 1995, the important distinction between through prodding rather than sec. 116). All this sets the stage merely doing research and punishment, convening groups of for a new paradigm for making attempting to apply research to doctors who treat specific research more useful to policing redirect professional practices. maladies to discuss the research than it has ever been before. One way to describe people evidence. These groups then who try to apply research is the produce their own consensus Key Questions role of “evidence cop.” More like guidelines for practices that a traffic cop than Victor Hugo’s become hospital policy. Thirty- In suggesting a new paradigm detective Javert, the evidence five such sets of guidelines were called evidence-based policing, cop’s job is to redirect practice produced in Weingarten’s first there are four key questions to through compliance rather than four years on the job (Millenson answer: What is it? What is new punishment. While this job may 1997, 120). about it? How does it apply to a be as challenging as herding cats, What NIH, Weingarten, and specific example of police it still consists of pointing the 1995 founders of the new practice? How can it be professionals to practice “this way, journal called Evidence-Based institutionalized? not that way.” As in all policing, Medicine are all trying to do is to the success rate for this job varies push research into practice. Just What is it? widely. Fortunately, the initial as policing has become more Evidence-based policing is the failures of people like Semmelweiss proactive at dealing with crime, use of the best available research paved the way for greater success researchers are becoming more on the outcomes of police work in the 1990s. proactive about dealing with to implement guidelines and Consider Scott Wein- practice. This trend has developed evaluate agencies, units, and garten, M.D.,