# Finding where criminals live by the numbers: mathematician combines calculations with geography.

WASHINGTON -- Math as a tool to track down criminals has never been as precise as the TV show NUMB3RS depicts. But mathematicians are developing better ways to estimate where a person on a crime spree might live.Using information about the layout of a city, such as the locations of similar crimes there in the past few years, beefed-up mathematical tools could improve estimates of where a criminal lives based on where he or she commits crimes, suggests research presented January 7 at the annual Joint Mathematics Meetings.

"I feel like I'm in a gold mine, and I'm the only one who knows what gold looks like," says Mike O'Leary, an applied mathematician at Towson University in Maryland who performed the new research. "There are so many good mathematical problems in this field" of criminology.

A well-established principle of criminology is that perpetrators will tend to commit more crimes close to their homes simply because of convenience and transportation realities. So older techniques estimate where a criminal lives based on the locations of unsolved crimes attributed to that criminal.

But those techniques ignore the actual layout of a city, instead assuming that the likelihood of a criminal striking near his or her home drops off evenly in all directions regardless of roads, neighborhoods, lakes and other geographical features.

"They don't have any way to incorporate yet data about geography," O'Leary says. "Mathematically they just don't have the tools for it."

To help find the perpetrator of a type of crime, such as robbing a convenience store, O'Leary's methods would use historical records of incidences of similar crimes to generate a likelihood distribution for that crime for the whole city. This distribution inherently contains information including where major roads and easy targets are located. The analysis also folds in census data about neighborhood demographics, as well as an analysis of how far from home criminals of different ages typically strike.

Other researchers have also developed software that attempts to incorporate this information. Until now, however, much of the research has been done by social scientists, comments Ned Levine, a geographical researcher at Ned Levine & Associates in Houston who developed crime-analysis software called CrimeStat. O'Leary has "added some insights into the mathematics that previously we were struggling with," Levine says. "He's really cleaning up the mathematics."

O'Leary is still working on the computer software that performs his analysis. The code for the software will be freely available, and the complete package will be free for police departments to use.

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Title Annotation: | Numbers |
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Author: | Barry, Patrick |

Publication: | Science News |

Geographic Code: | 1USA |

Date: | Jan 31, 2009 |

Words: | 417 |

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