Nodes, paths and edges: Considerations on the complexity of crime and the physical environment

Recent studies point to the potential theoretical and practical benefits of focusing police resources on crime hot spots. However, many scholars have noted that such approaches risk displacing crime or disorder to other places where programs are not in place. Although much attention has been paid to the idea of displacement, methodological problems associated with measuring it have often been overlooked. We try to fill these gaps in measurement and understanding of displacement and the related phenomenon of diffusion of crime control benefits. Our main focus is on immediate spatial displacement or diffusion of crime to areas near the targeted sites of an intervention. Do focused crime prevention efforts at places simply result in a movement of offenders to areas nearby targeted sites—“do they simply move crime around the corner”? Or, conversely, will a crime prevention effort focusing on specific places lead to improvement in areas nearby—what has come to be termed a diffusion of crime control benefits? Our data are drawn from a controlled study of displacement and diffusion in Jersey City, New Jersey. Two sites with substantial street-level crime and disorder were targeted and carefully monitored during an experimental period. Two neighboring areas were selected as “catchment areas” from which to assess immediate spatial displacement or diffusion. Intensive police interventions were applied to each target site but not to the catchment areas. More than 6,000 20-minute social observations were conducted in the target and catchment areas. They were supplemented by interviews and ethnographic field observations. Our findings indicate that, at least for crime markets involving drugs and prostitution, crime does not simply move around the corner. Indeed, this study supports the position that the most likely outcome of such focused crime prevention efforts is a diffusion of crime control benefits to nearby areas.

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Does crime just move around the corner? a controlled study of spatial displacement and diffusion of crime control benefits*

Hotspot mapping is a popular analytical technique that is used to help identify where to target police and crime reduction resources. In essence, hotspot mapping is used as a basic form of crime prediction, relying on retrospective data to identify the areas of high concentrations of crime and where policing and other crime reduction resources should be deployed. A number of different mapping techniques are used for identifying hotspots of crime – point mapping, thematic mapping of geographic areas (e.g. Census areas), spatial ellipses, grid thematic mapping and kernel density estimation (KDE). Several research studies have discussed the use of these methods for identifying hotspots of crime, usually based on their ease of use and ability to spatially interpret the location, size, shape and orientation of clusters of crime incidents. Yet surprising, very little research has compared how hotspot mapping techniques can accurately predict where crimes will occur in the future. This research uses crime data for a period before a fixed date (that has already passed) to generate hotspot maps, and test their accuracy for predicting where crimes will occur next. Hotspot mapping accuracy is compared in relation to the mapping technique that is used to identify concentrations of crime events (thematic mapping of Census Output Areas, spatial ellipses, grid thematic mapping, and KDE) and by crime type – four crime types are compared (burglary, street crime, theft from vehicles and theft of vehicles). The results from this research indicate that crime hotspot mapping prediction abilities differ between the different techniques and differ by crime type. KDE was the technique that consistently outperformed the others, while street crime hotspot maps were consistently better at predicting where future street crime would occur when compared to results for the hotspot maps of different crime types. The research offers the opportunity to benchmark comparative research of other techniques and other crime types, including comparisons between advanced spatial analysis techniques and predic-tion mapping methods. Understanding how hotspot mapping can predict spatial patterns of crime and how different mapping methods compare will help to better inform their application in practice.

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The Utility of Hotspot Mapping for Predicting Spatial Patterns of Crime

Motivated by empirical observations of spatio-temporal clusters of crime across a wide variety of urban settings, we present a model to study the emergence, dynamics, and steady-state properties of crime hotspots. We focus on a two-dimensional lattice model for residential burglary, where each site is characterized by a dynamic attractiveness variable, and where each criminal is represented as a random walker. The dynamics of criminals and of the attractiveness field are coupled to each other via specific biasing and feedback mechanisms. Depending on parameter choices, we observe and describe several regimes of aggregation, including hotspots of high criminal activity. On the basis of the discrete system, we also derive a continuum model; the two are in good quantitative agreement for large system sizes. By means of a linear stability analysis we are able to determine the parameter values that will lead to the creation of stable hotspots. We discuss our model and results in the context of established crim...

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A statistical model of criminal behavior

Originating with the Newark, NJ, foot patrol experiment, research has found police foot patrols improve community perception of the police and reduce fear of crime, but they are generally unable to reduce the incidence of crime. Previous tests of foot patrol have, however, suffered from statistical and measurement issues and have not fully explored the potential dynamics of deterrence within microspatial settings. In this article, we report on the efforts of more than 200 foot patrol officers during the summer of 2009 in Philadelphia. Geographic information systems (GIS) analysis was the basis for a randomized controlled trial of police effectiveness across 60 violent crime hotspots. The results identified a significant reduction in the level of treatment area violent crime after 12 weeks. A linear regression model with separate slopes fitted for treatment and control groups clarified the relationship even more. Even after accounting for natural regression to the mean, target areas in the top 40 percent on pretreatment violent crime counts had significantly less violent crime during the operational period. Target areas outperformed the control sites by 23 percent, resulting in a total net effect (once displacement was considered) of 53 violent crimes prevented. The results suggest that targeted foot patrols in violent crime hotspots can significantly reduce violent crime levels as long as a threshold level of violence exists initially. The findings contribute to a growing body of evidence on the contribution of hotspots and place-based policing to the reduction of crime, and especially violent crime, which is a significant public health threat in the United States. We suggest that intensive foot patrol efforts in violent hotspots may achieve deterrence at a microspatial level, primarily by increasing the certainty of disruption, apprehension, and arrest. The theoretical and practical implications for violence reduction are discussed.

http://ttaniguchi.net/wp-content/uploads/2014/08/Ratcliffe-et-al-2012-The-Philadelphia-Foot-Patrol-Experiment.pdf

The philadelphia foot patrol experiment: a randomized controlled trial of police patrol effectiveness in violent crime hotspots*

Patterns in crime

Using information gathered from police investigators' reports, this Article identifies some of the salient patterns and characteristics that differentiate forms of stranger rape, distinguish stranger from nonstranger rape, and distinguish serial from nonserial rape. The patterns and characteristics discussed reflect the situational nature of the offense, which is how the offender commits the offense, rather than descriptions of personal characteristics. These distinguishing patterns and characteristics also suggest why some stranger rapists are apprehended while others remain at large. The major framework utilized in distinguishing rape in this study is not solely based on victim-offender relationship. Rather the joint consideration of victim-offender relationship and the number of reported rapes committed by the same person before apprehension is suggested to better reflect the complex interplay between offender, victim, and situational characteristics and how they relate to the apprehension of the rape offender.

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James L. Lebeau

Papers

Patterns in crime

Patterns of Stranger and Serial Rape Offending: Factors Distinguishing Apprehended and at Large Offenders