The Hound of the Data Points

"This gives you an optimal search strategy," Rossmo says. "You search in the high areas first and then work your way downward." He rotates the plane in space, flipping it 180 degrees. "We make jokes about the seamy underside of cities."



The more data points -- encounter sites, body dump sites -- Rigel has to work with, the more accurate it is; which is to say, the smaller the impact of aberrations. Sometimes, when
Rossmo is constructing a profile and the number of points climbs beyond a dozen or so, something interesting happens: The hot zone stops moving. It's as if Rigel has laid its money down on the table.



For investigators, the value of a reliable hot zone is clear. If you can reduce a hunting area from, say, a hundred square blocks to two, all sorts of new strategies become available to the police: DMV checks of the cars in that neighborhood, door-to-door searches, even blanket collection of cheek swabs for DNA sampling. Flyers warning residents to be on the lookout are sometimes sent to all homes in the area. After they were convicted, the so-called Tag-Team Rapists of Surrey, Canada, admitted they actually received one, warning themselves about themselves.

Flashback to 1991: At the mammal hall at the Smithsonian National Museum of Natural History in Washington, regular museumgoers have begun to notice a guy hanging around suspiciously in the lion exhibit. Rossmo comes here whenever he's in town. He is working on his criminology doctoral thesis. He's trying to establish that a violent offender's movements through the city are almost entirely predictable -- and something he's learning here seems to help his case. Such "hunting patterns" seem to be universal. They even cross species boundaries.



In the lion kingdom there are "residents" that roam within a tight, circumscribed home range, and there are "nomads" that venture farther. There are times when a lion will meditatively plan its hunts, and times when dinner is fortuitously presented, as when a hartebeest or a dik-dik happens to wander into its domain. There are even times a lion will engage in what look like senseless spree killings -- charging and slaughtering as many as five animals in a single day, then leaving their uneaten carcasses to rot. The descriptions and m.o.'s fit almost perfectly with the typologies of human killers Rossmo was developing.



In The Serengeti Lion, which Rossmo had been reading, author George Schaller maps the travels of one nomadic male lion for nine days. The drawing looks vaguely like a daisy. The animal made foraging journeys in all directions, returning always to a tight cluster of rest sites -- a home base -- near the center. It brings to mind a geographic profile.



It was easy for Rossmo to jump cut, in the cinema of his mind, from the Serengeti plain to a quiet neighborhood in, say, Oak Park, Illinois. The killer driving past a row of apartment buildings looking for signs -- the curtains, the music, the scent of perfume issuing from an open window -- that this is the den of a single young female.