Truth Be Told

Virginia Hughes looks at the methods for detecting lies:

[T]here’s a huge problem with the polygraph: it’s all-too-frequently wrong. Truth-tellers may show a strong physiological response to being questioned if they’re nervous or fearful, which they often are — particularly if the target of a hostile interrogation. … Because of these considerable flaws, polygraph evidence is almost never allowed in court. But it’s still used routinely by federal law enforcement agencies, not only for screening accused criminals but potential new employees.

It turns out there’s a much more accurate way to root out deception: a 55-year-old method called the ‘concealed information test’. The CIT doesn’t try to compare biological responses to truth versus lies. Instead, it shows whether a person simply recognizes information that only the culprit (or the police) could know.

She considers why the CIT, employed frequently in Japan, hasn’t caught on in the US:

One reason, according to [John] Meixner, is that the CIT only works if it’s given at the very beginning of an interrogation. Otherwise, through the process of questioning, the suspect may gain knowledge about the crime that he or she didn’t have before. Investigators are “not especially keen on that.”

The CIT is also a bit less versatile than the traditional polygraph, because investigators have to know some hard facts about the crime before testing the suspect. In a real-world terrorism plot, for example, investigators wouldn’t necessarily know what city or month or weapon to ask about.

But the biggest reason we don’t use the CIT, according to Meixner and Rosenfeld, is probably cultural. As they wrote in a review paper last year: “The members of the practicing polygraph community simply do not like giving up [that] which they are used to.”