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Spatial planning, risk assessment

Doctoral students design online mapping system for tracking sex offenders


A team from Texas A&M University's College of Architecture is developing computerized mapping techniques to help police track locations and estimate risk-levels for registered sex offenders.

"We have created a spatial planning tool that law enforcement officers can use to locate sex offenders living in off-limits child safety zones," says Praveen Maghelal, doctoral student in planning in the Department of Landscape Architecture and Urban Planning. "Geographic information systems (GIS) technology provides a powerful means to map the addresses of such offenders and relate these locations to critical areas where children frequently gather."

"The system also is expected to help authorities provide timely proximity information about sex offenders living near the site of a child's disappearance, thus potentially contributing to quick solutions to such crimes," adds partner Miriam Olivares, also a doctoral student in planning.

Federal laws, such as the Sexually Violent Offenders Registration Act of 1994 and the 1996 Megan's Law, require those convicted of sexual crimes to register their places of residence with local law enforcement agencies, which then notify others residing in the neighborhood (within three blocks for subdivisions and within a one-mile radius for non-subdivided land) of the offender's presence. Most states also designate child safety zones near which offenders may not live, such as around daycare providers and schools.

Tracking such offenders has proven difficult, however, due to their mobility and to the fact that the size of child safety zones varies between different legal jurisdictions. In Texas, child safety zones are designated as "within 1,000 feet of premises including schools, day-care facilities, playgrounds, public or private youth centers, public swimming pools, and video arcade facilities, places where children generally gather."

Maghelal and Olivares used the GIS process of geocoding to locate all such facilities in Brazos County, the jurisdiction for which this system initially was developed; then they mapped the residences of the 164 sex offenders registered there in spring 2005. Working with the City of Bryan, which posted this information to the Web, the two graduate students made the resulting map available to both county law enforcement and the general public.

"Praveen and Miriam's project was more than just a database," says Doug Wunneburger, the research scientist who taught the GIS course for which it was developed. "Their analysis showed that a high percentage of registered sex offenders live in locations that violate restrictions against proximity to child safety zones. Their map allows members of the public to use the work as a planning tool to determine if sex offenders live near their homes or facilities used by their children. It can also help parole officers and sex offenders identify areas to avoid in finding a place for such offenders to live."

But Maghelal and Olivares did not stop at simply mapping where registered sex offenders live. They came up with a system for categorizing risk to communities caused by the presence of sex offenders.

"Based on the nature of a sex offender's offense, parole boards assign a risk level of low, medium or high," Maghelal explains. "Miriam and I have created an analysis system by overlapping and categorizing an individual offender's area of risk with child safety zones, which helps law enforcement gauge the cumulative risk to the community posed by individual offenders."

The students' approach was a novel one and has been praised by law enforcement officials.

"Prior to our study, no one had tried to understand the dynamic effect of the presence of sex offenders on the community," says Olivares. "Most studies had been done from the perspective of the sex offender's location or of concentrations of multiple registered offenders. But we looked at how to calculate for the community the accumulated threat based upon where sex offenders live."

The students' class project has turned into quite an enterprise. Olivares and Maghelal have presented papers about the project at the National Institute of Justice's Crime Mapping Research and ESRI Conferences, at the Texas A&M Pathways Student Research Symposium, where it was awarded first place for graduate research, and at the university's Student Research Week, where it also won first place for oral presentation. In addition, the web-based service developed by the City of Bryan as a result of the student's work has received coverage on national television. Now, Maghelal and Olivares are hoping to work with other communities to analyze the risk imposed due to the presence of registered sex offenders.

"I think the most interesting aspect of Praveen and Miriam's GIS mapping and risk assessment methodology is its potential for evaluating the benefits of the current law-making trend to mandate large child safety zones," notes Wunneburger.

"Can such practices help prevent sex crimes? If so, could similar methods be applied to prevent or limit impacts of other crimes, such as DWI offenses? These two students have already established their proficiency in addressing such questions."

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