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Returning to the Scenes of the Crime

POLICE DEPARTMENTS used to track neighborhood crime by placing pushpins at crime locations on a wall map. Now crime tracking has become far more sophisticated.

Today, law enforcement analysts around the country depict crime “hot spots” through specialized tools. They are able to calculate trends and graphically depict them via color-gradient dots, standard-deviation ellipses, spatial autocorrelation techniques, and isolines. Collectively, these techniques are referred to simply as crime mapping.

A report by the National Institute of Justice escorts readers through a progressively more complex approach to mapping and analysis.

The report provides an overview of crime mapping, explaining when one might want to use dots, lines, or ellipses to designate hot zones, depending on whether the goal is to identify victimization trends, specific crime scenes, or neighborhoods with high crime or disorder.

The authors also explain complex issues, such as Moran’s I and Geary’s C Statistic—spatial autocorrelation techniques that test whether the distributions of crimes are related to each other.

The presentation further explores how geographic information systems software enhances crime analysis, with the focus on four available programs. One tool, for example, excels at representing the spatial distribution of aggregated crime data in specific bounded geographic areas, while another is best used to map the density of individual crimes on a more graduated basis irrespective of the specific boundaries in question.