In a low-income Massachusetts apartment complex that never before saw enough crime to grab the attention of its owner's safety director, property managers suddenly were scrubbing graffiti from hallway walls every morning. Residents feared the colorful drawings and scribbled slang were evidence that gangs roamed the inner-city complex during the night.

Managers there were primed to call the cops, step up security, and train cameras on every hallway in their quest to catch the graffiti artists. But when they approached Thaddeus Miles, director of public safety for the quasi-governmental Mass Housing—which oversees that property and 600 others around the state—he had another idea.

Miles reviewed a history of the complex's crime reports and asked a security vendor to work up a profile of criminal activity in the surrounding neighborhood over the past year. Both reports turned up empty: no gang activity, assaults, or robberies.

A bit of sleuthing uncovered the culprits: Crayon-wielding 9- and 10-year-olds “at that ‘wannabe' stage” who were unsupervised in the afternoons, recalls Miles. “There wasn't any green space, and you had a lot of kids. They didn't have anything else to do.”

They do now: Miles installed a computer room on the premises and invited the local college to send its education majors over after school to teach the kids about technology. The graffiti is gone.

Miles' method is called crime mapping—using prior crime statistics from the apartment complex and its neighborhood to predict the community's risk for future trouble. Combined with background checks of potential tenants and other routine prevention strategies, crime mapping can contribute significantly to a risk-assessment plan that helps a safety staff decide where it needs heavier or lighter security.

“One of the best ways to predict annual crime rates is to know what the crime rate was the year before,” notes Matthew Giblin, an assistant professor of criminal justice at York College in Pennsylvania.

Evaluating the Risk Crime mapping's crystal ball has been embraced by risk assessors responsible for security at hotels, banks, college campuses, and, on a more limited basis, multifamily companies. Just half a dozen multifamily companies use the technology as part of their security strategies, compared with 21 of the top 25 Fortune 100 companies that subscribe to crime maps and reports from Exton, Pa., vendor CAP Index, says company president Jon Groussman.

The service scores a property's risk for homicide, rape, robbery, aggravated assault, burglary, larceny, and car theft using police reports, FBI statistics, loss reports from the company's own clients, and offender and victim surveys. It also mixes in demographic data about the neighborhood: education and income levels; how transient the population is; and what kind of housing surrounds the property.

The local score compares the property's risk with sites around the country, in the state, and in the county.