The Hound of the Data Points

And yet: Early on in the rampage, Rigel guessed the sniper's anchor point to be somewhere in the northern suburbs of D.C. (It turned out, in fact, that the killers may have had no anchor point at all.) It's tough to say whether it hurts or helps Rossmo's cred to point out that every pseudo-profiler who went on a TV news show with a half-cocked opinion was spectacularly wrong. In any case, though, when an anonymous tip attributed to the snipers gave police the clue they needed, the solution still seemed to be a long way away, buried deep in those 15,000 daily tips and an armada of irrelevant white vans.



"There are instances where profiling will probably be quite helpful, and there are a lot where it doesn't work at all," says Keith Harries, a professor of geography at the University of Maryland Baltimore County and a pioneer in "geography of crime" research. "In the sniper case, [Rossmo's algorithm] was just not able to handle the level of variation in the data."



As Ned Levine, a Houston-based urban planner who himself developed a geographic profiling model called Crimestat for the National Institute of Justice, points out, the two men arrested in the sniper case, John Allen Muhammad and John Lee Malvo, never kept a home base for long. (They had lived most recently in Washington state.) The distances they traveled were so large as to make the models imprecise. They killed not in areas they knew, but in areas like areas they knew. Which, in increasingly homogeneous America, can encompass quite a lot of real estate. Itinerant assassins like Andrew Cunanan and Aileen Wuornos have resisted accurate geoprofiling. (Evidence shows that U.S. serial killers are almost twice as nomadic as serial killers from elsewhere.) The increasing mobility of offenders and the increasing complexity of travel patterns could, Levine suggests, create ever-larger problems for geoprofilers.



Rigel retails for around $55,000. Two full years of study directly under Rossmo or someone he has trained are required to use it. That's why an exclusive club of only seven agents in the world, within the Royal Canadian Mounted Police, the Bureau of Alcohol, Tobacco and Firearms, Scotland Yard and the Ontario Provincial Police force, are certified to handle Rigel. The premise is that, as with fingerprint analysis, the interpretation is only as good as the interpreter. The raw algorithm can be quite far off, but a properly trained profiler
can account for vagaries of terrain and travel methods and criminal behavior. That's the art. And that, Rossmo might say, is what separates his system from the cruder, plug-in-the-numbers-and-let-rip alternative models that have sprung up since Rossmo's company patented Rigel in 1996.



Rossmo's competitors assert Rigel hasn't yet proven itself. In the long run, they believe, Rossmo's model will reveal itself as no more accurate than their own -- indeed no more accurate than straight centrography, the old pushpin method. "The business of the training is a way of making it seem terribly special and exotic, and imply that there are all sorts of skills that they can charge a lot of money for," says David Canter, director of the Center for Investigative Psychology at the University of Liverpool, who sometimes makes his own program, Dragnet, available free to researchers as open-source software. No one has ever done a head-to-head comparison of all the competing models, but, says Levine, "it's certainly overdue."



Rossmo says he can't discuss the Beltway Sniper case in any detail, in part because he doesn't have all the details about the suspects' movements throughout the killing spree. But he is pretty sure that Rigel wasn't as wrong-footed as it appeared. "Based on everything I know, the patterns of their behavior seemed, geographically, to be what we expected. That's all I'll say. I didn't find anything very surprising." In any case, he says, with any methodology there are assumptions and limitations. "I'd say of the requests I've received, 85 percent of the time we could provide some help," he says.



Back in Rossmo's office, the phone rings again: It's a request for him to speak at a university. It's not hard to imagine
Rossmo standing in front of the students and driving home a key point: Remember, folks, how probabilities work. Bet with the odds but put a fifty in a coffee can. There are times when insurance companies have to fork out a big settlement. There are days when it does rain in Southern California, and moments when broken clocks tell Greenwich Mean Time. There are stories where the Mounties don't always get their man.

Bruce Grierson lives in Vancouver and has written for numerous publications, including The New York Times Magazine.