Investigators are using the software to try to pinpoint the killer's home base.
Law enforcement officials are hoping the system, one of the latest crime-fighting techniques, will help them home in on a suspect, who so far has shot and killed at least six people in the past week while they performed mundane tasks such as gassing up a car, mowing the lawn, or loading packages into a trunk.
The Rigel system, created by Environmental Criminology Research (ECRI), works on the assumption that a person performing a task will expend the least amount of effort possible to complete it. That is, criminals don't want to go farther than necessary to commit a crime, but they don't want to do it too close to home, where they could be recognized.
"People aren't very good at truly randomizing what they do," said Ian Laverty, president of ECRI.
The Java-based technology, which was introduced five years ago as the first geographic profiling software, runs a series of complex mathematical formulas on the locations of a set of related crimes. The program then generates a 3-D multicolored chart indicating the probability that a criminal was operating from a certain location.
The algorithms are based on research on a wide variety of topics, including criminology, behavioral psychology, and an examination of the hunting patterns of lions.
The software isn't designed to solve a crime single-handedly. Instead, it can provide police with a starting point by alerting them, for example, that it might be helpful to go door-to-door in a certain neighborhood and ask residents about suspicious behavior.
"What we're trying to do is help investigators prioritize," Laverty said.
The system is the brainchild of former police detective Kim Rosso, who is now the research director at the Police Foundation and is helping investigators create a geographic profile of the Washington-area sniper.
Fewer than a dozen people are trained to use the complex high-end system, which costs about $50,000 and is geared toward serial violent crimes. The company also offers a lower-end system for $5,700 that's designed for the investigation of property crimes.
The system has been used in 500 to 700 cases so far, ranging from serial rapes, murders and arsons to vandalism. Rigel has helped to resolve about 150 of the cases, the company said.
Narrowing the suspects
Sgt. Brad Moore, a trained Rigel profiler who works with the Ontario Provincial Police, said the software helps whittle down a suspect list, much as psychological profiling does.
For example, he was working on a case of serial rapes in a town outside of Toronto where police had a list of 300 suspects. The profiling software pointed to one man, and DNA evidence linked him to the crime.
"We offer the answer to one of the fundamental questions, and that is 'where is the offender?'" he said.
Moore also used Rigel in a high-profile case in Lafayette, La., in which a police officer was eventually convicted of a string of serial killings during an 11-year period. In that case, the software accurately identified the region where the suspect lived, although other leads resulted in his arrest.
Moore said the software is just one piece of the crime-fighting puzzle. After crunching the geographic numbers, investigators compare the information generated to more traditional data such as thumbprints, blood spatter analysis, ballistics studies, and tips from citizens.
What's more, geographic profiling data doesn't stand up in court in the same way that, say, DNA evidence does.
Still, investigators say the system is a solid investigative tool that could assist police as they try to narrow in on the Washington-area sniper despite their lack of leads in the killing spree. What's more, the system only gets more accurate as the shooter commits more crimes and provides more data points.
For example, a criminal who meets a victim in one location, commits the crime in another, and then disposes of the body in a third spot, may think he's covering his tracks--but he's actually adding three nodes of information to a geographic profiler's database.
In the case of the Washington-area sniper, investigators can look not only at the locations of the shootings, but also the spot where the shooter has reportedly dropped a calling card taunting police and telling them "I am God." Although a criminal may think he or she is throwing investigators off the scent, such actions instead form a pattern the software is designed to detect.