Brandon C. Welsh’s research while affiliated with Northeastern University and other places

This paper summarizes the main fmdings of what works, what does not work, and what is promising in preventing crime, and discusses the implications for public policy. The findings are based on the book Evidence-Based Crime Prevention, published in 2002. The book's aim was to update and substantially revise the 1997 report, Preventing Crime : What Works, What Doesn't, What's Promising, by Lawrence Sherman and his colleagues at the University of Maryland. An analysis of nearly 700 program evaluations found that 29 program types worked, 25 did not work, and 28 were promising in preventing crime. These results suggest that we know a fair amount about how to prevent crime. Results also suggest three broad-based courses of action : (1) we need to increase resources devoted to those program types with demonstrated effectiveness in preventing crime; (2) we need to stop funding those program types with proven evidence of ineffectiveness; and (3) we should begin further testing of those program types that are promising.

This paper summarizes the main findings of what works, what does not work, and what is promising in preventing crime, and discusses the implications for public policy. The findings are based on the book Evidence-Based Crime Prevention , published in 2002. The book’s aim was to update and substantially revise the 1997 report, Preventing Crime : What Works, What Doesn’t, What’s Promising , by Lawrence Sherman and his colleagues at the University of Maryland. An analysis of nearly 700 program evaluations found that 29 program types worked, 25 did not work, and 28 were promising in preventing crime. These results suggest that we know a fair amount about how to prevent crime. Results also suggest three broad-based courses of action : (1) we need to increase resources devoted to those program types with demonstrated effectiveness in preventing crime; (2) we need to stop funding those program types with proven evidence of ineffectiveness; and (3) we should begin further testing of those program types that are promising.

Research summary A long‐standing critique of place‐based crime prevention interventions has been that any reductions in crime are often short‐lived. If researchers do not carry out longer‐duration follow‐ups, we cannot know for sure if the effects of these interventions will persist, decay, or even strengthen. Using a rigorous microsynthetic control design, we evaluated the long‐term impacts of a large‐scale, public‐area closed‐circuit television (CCTV) surveillance project in Newark, New Jersey. Results show that the CCTV project was associated with a statistically significant reduction of auto theft in the intermediate term (3–4 years). The reduction of auto theft approached statistical significance ( p = 0.08) during the short term (1–2 years). The analysis also observed potential displacement effects, with displacement of robbery ( p = 0.09) in the short term (1–2 years) and theft from auto ( p = 0.06) in the long term (9–11 years) approaching statistical significance. Policy implications The results of this study may suggest the potential for a slightly modified view of deterrence decay. The CCTV project's effect on auto theft grew from approaching significant to statistically significant between the short‐term and intermediate‐term periods. Such “sleeper effects” suggest that an extended period was necessary for CCTV to generate deterrence. The deterrence decay during the long‐term period did not occur until after these sleeper effects emerged, which may be understood as deterrence attenuation. Although only approaching statistical significance—and not as pronounced as the reduction of auto theft—the potential displacement of robbery and theft from auto indicates that static CCTV target areas may facilitate offenders taking advantage of nearby crime opportunities while appearing inconspicuous within CCTV viewsheds. In sum, policymakers should be mindful that research evidence limited to short‐term impacts may fail to detect nuanced effects relevant for policy and public guidance.

Background David Farrington (1944–2024) wrote extensively about the methodological rigour and utility of the longitudinal‐experimental research design to advance knowledge about the development, explanation, prevention and treatment of antisocial behaviour and criminal offending over the life‐course. Founded in 1935, the Cambridge‐Somerville Youth Study (CSYS) is recognised as the first randomised controlled trial in criminology and the first longitudinal‐experimental study in criminology. Aims To report on key scientific and policy contributions made by the CSYS in investigating the development and prevention of delinquency and criminal offending over the life‐course. Methods Uses previously analysed observational and experimental data from follow‐ups of study participants conducted in middle age ( N = 494; mean = 47 years) and old age ( N = 488; 84–92 years). Results Identified several parental socialisation practices and interactions during childhood (but not father absence) as strongly associated with serious criminal offending in middle age. Support for peer deviancy as a causal mechanism for iatrogenic effects among treatment groups, compared to pair‐matched controls, during middle age drew policy attention to group‐based prevention interventions. Conclusions The longitudinal‐experimental design is a highly important yet under‐utilised methodological approach in criminology. Future research should include revisiting the original plan for the design, addressing a key potential concern of the design and carrying out longer follow‐ups at key stages of the life‐course.

Research Summary Broken windows theory suggests that police can prevent serious crime by addressing social and physical disorder in neighborhoods. In many U.S. cities, recent increases in disorder, fear, and crime have initiated calls for an intensification of disorder policing efforts. Disorder policing programs can be controversial, with evaluations yielding conflicting results. Further, a growing number of descriptive analyses of aggressive order maintenance programs raise concerns over varied negative consequences, such as increased racial disparities in arrests of citizens. Systematic review and meta‐analytic techniques were used to conduct an updated analysis of the effects of disorder policing on crime. Fifty‐six eligible studies including 59 independent tests of disorder policing interventions were identified, representing almost twice the number included in the previous review. As part of the meta‐analysis, new effect size metrics were used. The updated meta‐analysis suggests that policing disorder strategies are associated with overall statistically significant crime reduction effects that spill over into surrounding areas. The strongest program effect sizes were generated by community and problem‐solving interventions designed to change social and physical disorder conditions at crime hot spots. Conversely, aggressive order maintenance strategies did not generate significant crime reductions. Policy Implications The types of strategies used by police departments to address disorder seem to matter in controlling crime, and this holds important implications for police–community relations, justice, and crime prevention. Further research is needed to understand the key programmatic elements that maximize the capacity of these strategies to prevent crime.