60 Fighting Crime With Mathematics

One major problem in crime-fighting is that a police crackdown in one neighborhood may simply push criminal behavior into a nearby area. In March two mathematicians, working with an anthropologist and a criminologist, announced a way to quantify this reaction. “Crimes tend to cluster together in space and time, forming hot spots,” says UCLA mathematician Martin Short, the study’s lead author. Drawing on real-world data, his team developed a model showing that hot spots come in two varieties. One type forms when an area experiences a large-scale crime increase, such as when a park is overrun by drug dealers. Another develops when a small number of criminals—say, a pair of burglars—go on a localized crime spree. The model suggests that a focused police response can relatively easily extinguish larger hot spots because the criminals there scatter randomly, making it unlikely that they will resume coordinated unlawful activity nearby. But for smaller crime waves, crooks just migrate together into an adjacent neighborhood, where they are likely to start another spree. By analyzing police reports as they come in, Short hopes to determine which type of hot spot is forming so police can handle it more effectively. DANIEL LAMETTI