A criminologist reviews 70 years of evidence on how to prevent crime.
There is a growing body of evidence that politically popular justice reform efforts, such as raising the maximum age under which someone can be handled in the juvenile justice system, are proving to make no difference or even increase the risk of recidivism. Policies and programs for criminal justice reform should be guided by scientific evidence, not wishful thinking about what may work in a Utopian world. As Thomas Sowell notes, “When you want to help people, you tell them the truth. When you want to help yourself, you tell them what they want to hear” The field of experimental criminology should continue to embrace evidence-based policy and push back against “replacing what worked with what sounded good.”
The field of experimental criminology has become influential in designing, testing and evaluating criminal justice reforms and reporting their results, even when results are contrary to popularly held beliefs. After all, science advances by trial and error and generating findings sometimes that are at odds with prevailing beliefs. Science is about generating objective evidence. The only faith required is the belief in the scientific method. Findings should be objective as possible, recognizing that choices of statistical analyses and program evaluation designs can change findings. Hence the need for replication of results in other settings and reproductions of results when new methods develop.
In the context of criminal justice reform, social programs that do not show evidence of being effective at reducing crime or that increase crime should be redesigned or abandoned, regardless of political popularity. The esteemed economists John Maynard Keynes and Milton Friedman rarely agreed, but there are two quotes that offer useful guides for criminal justice reform efforts. John Maynard Keynes is attributed as stating “When the facts change, I change my mind — what do you do, sir?” Similarly, Milton Friedman stated, “One of the great mistakes is to judge policies and programs by their intentions rather than their results.”
Criminal justice reform should be guided by evidence, not ideology, anecdote or magical thinking.
Criminal justice reform efforts should be guided by a basic understanding of the facts of crime and criminal offenders, and by scientific findings from social programs that have been shown to prevent crime and minimize the use of the criminal justice system. Over 100 hundred years of research has revealed seven indisputable facts about crime and offenders:
First, crime is highly concentrated by place. As little as 3% of addresses and 5% of street blocks account for more than 50% of crimes reported by citizens to the police. The concentration of crime is even greater if one focuses on more serious crimes that are less subject to under-reporting, such as shootings and homicides.
Second, crime is also concentrated by times of day, days of the week and months. Summers, nights and weekends are peak times for violence. Burglaries happen during the middle of the day when homes are empty and people are away at work, school, or on errands.
Third, crime is highly concentrated among active offenders. Most of the criminal offending in the population is generated by a small fraction of chronic offenders, such that the incapacitation of one high-volume offender abates an estimated 9.4 felony offenses.
Fourth, just as crimes are highly concentrated among places and people, so are the social costs of crime. A subset of serious crimes generates the most harm. Social costs of crime derived from jury awards, the willingness to pay to avoid specific crimes, costs to victims, criminal justice system costs and from sentences imposed for a given offense all show that violent crimes are the costliest.
Fifth, among criminal offenders, the rate of offending peaks in early adulthood, consistent with the “age-crime curve.”
Sixth, offenders do not specialize in specific offense patterns. Rather, active offenders tend to engage in what could be called a “cafeteria style” of offending and select a lot of different offenses from a menu of options. While some offenders show repeat behaviors, even the most optimistic approaches to estimating offense specialization can only find some modest evidence of offending preferences.
Seventh, criminal offending occurs within social networks, and the most active offenders tend to be clustered within dense criminal networks.
One can debate about which theories explain these facts the best, but the facts are indisputable. They exist across time periods, demographic groups, countries and whether crime is measured by official records or self-reported offending and victimization.
The most convincing rigorous evidence that exists focuses on fostering informal and formal social control.
Evidence-based crime policy should be guided by programs that confront these basic facts. The best evidence to guide policy are programs or interventions that have been experimented with in the real world, are attuned to the distribution of crime and offenders, can be scaled up to the population, are sustainable and are constitutional. We are fortunate that criminology has generated an abundance of experimental and quasi-experimental evidence over the past 70 years for what works to prevent crime. This evidence, however, has been largely absent from the current policy debates on criminal justice reform. A truly progressive criminal justice reform should be guided by evidence, not ideology, anecdote, or magical thinking.
The most convincing rigorous evidence that exists focuses on fostering informal and formal social control. Social control focuses on the constrained view of human behavior, or that society must control places and people to have a lawful society. Informal social control typically refers to the spectrum of actions taken by family, friends, neighbors and schools to maintain norms and rules. Formal social control refers to the exercise of the state to use sanctions or the threat of sanctions to enforce norms to prevent crime and illegal conduct. In conventional terms, formal social control is expressed through the functions of police, prosecutors and judges, and includes the other mechanisms of the criminal justice system.
Informal and formal social control are clearly linked to each other. While community safety is primarily produced by informal social control, high-crime areas are in particular need of formal social control like the presence of effective police and prosecutors when neighbors are unable to regulate the conduct of public spaces. So why have progressive criminal justice reforms in the past several years forgotten about social control?
The current state of progressive criminal justice policy reforms seems to have missed the growth of evidence-based policy generated from several decades of experimental and quasi-experimental evaluations in criminology.
This is a rhetorical question, as I realize there is another view about the causes of crime that focus on crime as a social construct and criminal offending as solely a result of social inequality. Under this worldview, addressing crime requires redressing the social origins of crime. While the social origins of crime, such as concentrated disadvantage, can be viewed as “root causes,” we have few experimental or quasi-experimental evaluations of social programs that address root causes and show appreciable changes in the concentration of crime by place, among active offenders and within offending networks. There are programs and policies that can help reduce social inequalities and help mitigate crime, but they are longer-term investments and not the proximal causes of changes in the crime rate in each period.
Criminal justice reform needs to be tailored to the present facts on the ground. The facts of crime in the moment need to be responded to with efforts that prevent crime and not ignore those efforts in the hope for a more promising distant future. Moreover, there is no logical reason that policies cannot address both the current facts of crime in the population and longer-term efforts to reduce future cohorts from experiencing surges in crime and violence. A criminal justice reform effort that is effective at controlling crime with the minimum use of punishment necessary should be guided by evidence on what drives the crime rate and what can reduce inequalities in the criminal justice system.
A close review of experimental and quasi-experimental evaluations offers support for the following social programs that focus on those at greatest risk of serious criminal offending, the concentration of crime by place and the networked nature of offending:
Family: Functional Family Therapy, Multi-systemic Therapy and Nurse Family Partnership all are programs that have been demonstrated to work through at least one high-quality randomized controlled trial among at-risk youth. All these programs focus on teaching parenting skills and increasing pro-social thinking among youth.
Schools: School-based programs that have demonstrated efficacy similarly involve teaching thinking skills to constrain aggressive or criminal behavior. Such programs include Life Skills Training, Positive Action and Becoming a Man. These programs focus on social control, helping youth learn self-control and increasing bonds to school.
Places: Summer jobs for at-risk youth are delivered to youth in communities with the highest rates of crime and violence and thus fit within the general framework of establishing social control in places. These programs help keep kids off the streets in the summer with productive things to do. Also, having adults monitor youth in actual jobs is another form of informal social control. Business improvement districts (BIDs), for example, are a social program that involves local businesses organizing in a defined geography and hiring private security guards and CCTV cameras, cleaning crews and place promotion and marketing materials to make a commercial area look and feel safer. The key logic model of BIDs is the focus on reducing physical disorder in places and offering extra “eyes upon the street.” Other social programs that focus on the physical environment and offer evidence for reducing serious crime include vacant lot greening and vacant housing remediation, improving street lighting and nuisance abatement.
Criminal Justice Agencies: Social control from criminal justice agencies may be one of the least popular social programs among contemporary criminal justice reformers, but it is an area where we have arguably the best evidence. This includes support for deploying extra police to crime “hot spots” — when police stay vigilant about crime prevention in crime hot spots, they exert a significant impact on serious crime and violence. The theoretical logic of hot spot policing is also consistent with the offender-specific program of focused deterrence, a multi-stakeholder approach that involves providing direct deterrence messages to individuals with high rates of offending. Rigorous designs that compare cities with and without focused deterrence or groups of offenders that could have been eligible find that when the program is implemented with fidelity, it significantly reduces serious crime and violence. Research from several quasi-experimental studies also suggests that increasing prison time for active offenders also helps prevent crime.
The current state of progressive criminal justice policy reforms seems to have missed the growth of evidence-based policy generated from several decades of experimental and quasi-experimental program and policy evaluations in criminology. Ideally, criminal justice policy reforms should be logically consistent with facts of crime and criminal offenders, tested in the field and implemented gradually.
By contrast, closing down summer job programs, letting physical disorder and mismanagement of places spread in neighborhoods, having the police pull back from high-crime intersections and the criminal justice system failing to hold active offenders accountable are all examples of ways to foster epidemic rises in serious crime and violence. These results were witnessed during the 2020–2021 rise in violent crime in large U.S. cities, but also echo the patterns of other violent crime cycles in American history.
Understanding the basic facts of crime and offenders explains why social programs that foster informal and formal social control and are targeted to those individuals and places at the greatest risk for criminal offending generate sizable reductions in serious crime. We have good evidence for social programs that work to prevent crime and minimize the footprint of the criminal justice system. This evidence base offers good guidance for effective criminal justice reforms. I am hopeful that the evidence generated from experimental criminology on what works to prevent crime can have a greater impact in the future than it presently has received from the policy community.