Thursday, November 15, 2007

FBI Profiling

Malcolm Gladwell on the flaws of criminal profiling;

Not long ago, a group of psychologists at the University of Liverpool decided to test the F.B.I.’s assumptions. First, they made a list of crime-scene characteristics generally considered to show organization: perhaps the victim was alive during the sex acts, or the body was posed in a certain way, or the murder weapon was missing, or the body was concealed, or torture and restraints were involved. Then they made a list of characteristics showing disorganization: perhaps the victim was beaten, the body was left in an isolated spot, the victim’s belongings were scattered, or the murder weapon was improvised.

If the F.B.I. was right, they reasoned, the crime-scene details on each of those two lists should “co-occur”—that is, if you see one or more organized traits in a crime, there should be a reasonably high probability of seeing other organized traits. When they looked at a sample of a hundred serial crimes, however, they couldn’t find any support for the F.B.I.’s distinction. Crimes don’t fall into one camp or the other. It turns out that they’re almost always a mixture of a few key organized traits and a random array of disorganized traits. Laurence Alison, one of the leaders of the Liverpool group and the author of “The Forensic Psychologist’s Casebook,” told me, “The whole business is a lot more complicated than the F.B.I. imagines.”

Alison and another of his colleagues also looked at homology. If Douglas was right, then a certain kind of crime should correspond to a certain kind of criminal. So the Liverpool group selected a hundred stranger rapes in the United Kingdom, classifying them according to twenty-eight variables, such as whether a disguise was worn, whether compliments were given, whether there was binding, gagging, or blindfolding, whether there was apologizing or the theft of personal property, and so on. They then looked at whether the patterns in the crimes corresponded to attributes of the criminals—like age, type of employment, ethnicity, level of education, marital status, number of prior convictions, type of prior convictions, and drug use. Were rapists who bind, gag, and blindfold more like one another than they were like rapists who, say, compliment and apologize? The answer is no—not even slightly.

“The fact is that different offenders can exhibit the same behaviors for completely different reasons,” Brent Turvey, a forensic scientist who has been highly critical of the F.B.I.’s approach, says. “You’ve got a rapist who attacks a woman in the park and pulls her shirt up over her face. Why? What does that mean? There are ten different things it could mean. It could mean he doesn’t want to see her. It could mean he doesn’t want her to see him. It could mean he wants to see her breasts, he wants to imagine someone else, he wants to incapacitate her arms—all of those are possibilities. You can’t just look at one behavior in isolation.”

A few years ago, Alison went back to the case of the teacher who was murdered on the roof of her building in the Bronx. He wanted to know why, if the F.B.I.’s approach to criminal profiling was based on such simplistic psychology, it continues to have such a sterling reputation. The answer, he suspected, lay in the way the profiles were written, and, sure enough, when he broke down the rooftop-killer analysis, sentence by sentence, he found that it was so full of unverifiable and contradictory and ambiguous language that it could support virtually any interpretation.

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