This popular police "mindreading" technique is bullshit but the things that cops say about it are somehow even worse.

Back in December, ProPublica published a fascinating look into the snake-oil industry around Scientific Content Analysis or SCAN, a so-called "law enforcement tool" that purports to help investigators determine whether their suspects lying. This highly-profitable yet totally-dubious training method works through a rigid grammar analysis that relies entirely on the assumption that human brains only ever work in one completely uniform, logical, rational, conscious, and deliberate manner:

With SCAN, Sapir encourages the asking of a simple, open question: What happened? After the person writes a statement, the SCAN investigator looks for signs of deception, analyzing, among other things, pronouns used, changes in vocabulary, whats left out and how much of a statement is devoted to what happened before, during and after an event. Indications of truthfulness include use of the past tense, first-person singular (I went to the store); pronouns, such as my, which signal commitment; and direct denials, the best being: I did not do it. Signs of deception include lack of memory, spontaneous corrections and swapping one word in for another for example, writing kids in one place and children in another.

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Sapir likens SCAN to Sudoku, only with words, not numbers, sentences, not squares: Everything must fit left to right, and top to bottom.

And of course, there's no consideration for the possibility that someone might be, idunno, nervous oranxious or god forbidunder-educated and therefore might respond to this "test" in ways that seem arbitrarily "suspicious."

Yet there are still tons of cops who swear by it anyway even though, as ProPublica reveals through a comprehensive analysis of SCAN test results, the system has about a 50 percent likelihood of accurately predicting whether a suspect is lying, which is no better than a random guess. Read the rest