The truth about criminal profiling

Malcolm Gladwell has a fascinating and important article on criminal profiling:

Dangerous Minds

He is not impressed by the "science" or the results:

In the case of Derrick Todd Lee, the Baton Rouge serial killer, the F.B.I. profile described the offender as a white male blue-collar worker, between twenty-five and thirty-five years old, who “wants to be seen as someone who is attractive and appealing to women.” The profile went on, “However, his level of sophistication in interacting with women, especially women who are above him in the social strata, is low. Any contact he has had with women he has found attractive would be described by these women as ‘awkward.’ ” The F.B.I. was right about the killer being a blue-collar male between twenty-five and thirty-five. But Lee turned out to be charming and outgoing, the sort to put on a cowboy hat and snakeskin boots and head for the bars. He was an extrovert with a number of girlfriends and a reputation as a ladies’ man. And he wasn’t white. He was black.

A profile isn’t a test, where you pass if you get most of the answers right. It’s a portrait, and all the details have to cohere in some way if the image is to be helpful. In the mid-nineties, the British Home Office analyzed a hundred and eighty-four crimes, to see how many times profiles led to the arrest of a criminal. The profile worked in five of those cases. That’s just 2.7 per cent, which makes sense if you consider the position of the detective on the receiving end of a profiler’s list of conjectures. Do you believe the stuttering part? Or do you believe the thirty-year-old part? Or do you throw up your hands in frustration?

[snip]

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.

Astrologers and psychics have known these tricks for years. The magician Ian Rowland, in his classic “The Full Facts Book of Cold Reading,” itemizes them one by one, in what could easily serve as a manual for the beginner profiler. First is the Rainbow Ruse—the “statement which credits the client with both a personality trait and its opposite.” (“I would say that on the whole you can be rather a quiet, self effacing type, but when the circumstances are right, you can be quite the life and soul of the party if the mood strikes you.”) The Jacques Statement, named for the character in “As You Like It” who gives the Seven Ages of Man speech, tailors the prediction to the age of the subject. To someone in his late thirties or early forties, for example, the psychic says, “If you are honest about it, you often get to wondering what happened to all those dreams you had when you were younger.” There is the Barnum Statement, the assertion so general that anyone would agree, and the Fuzzy Fact, the seemingly factual statement couched in a way that “leaves plenty of scope to be developed into something more specific.” (“I can see a connection with Europe, possibly Britain, or it could be the warmer, Mediterranean part?”) And that’s only the start: there is the Greener Grass technique, the Diverted Question, the Russian Doll, Sugar Lumps, not to mention Forking and the Good Chance Guess—all of which, when put together in skillful combination, can convince even the most skeptical observer that he or she is in the presence of real insight.