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How to Spot a Terrorist on the Fly

We also looked at the behavioral signs that accompany the act of thinking up an answer on the spot (e.g., an increase in pauses) and signs of emotion in the face, voice or gesture that contradict the words being spoken ("The answer is definitely no" accompanied by just a slight nod of the head).

The facial expressions we identified allowed us to correctly determine who was lying 70 percent of the time; when the rest of demeanor is added, it pushes accuracy close to 100 percent.

Tools like this are indispensable to the future of airport security, and more are coming. Within the next year or two, maybe sooner, it will be possible to program surveillance cameras hooked to computers that spit out FACS data to identify anyone whose facial expressions are different from the previous two dozen people in line.

Someday, remote surveillance devices may identify anyone whose blood pressure and heart rate are much higher than those of the previous two dozen people. While this will provide an important new way of knowing that something is amiss, it does open a Pandora's box. Legislation to protect privacy and prevent misuse of such a technique should be enacted now.

Meanwhile, short-term research on several questions -- whether SPOT misses people whose behaviors are on its checklist; whether other behaviors should be included on the list; and whether additional training would increase observers' accuracy -- could help improve the program.

Civil libertarians have raised the expected concerns about using observational techniques at airports: that SPOT spots more than just terrorists; that minorities, who fear discrimination and might act more nervous than others, may be unfairly singled out; that most of the people identified are innocent.

But the day I spent at Logan confirmed for me that SPOT violates no one's civil rights. Few people were identified. Nearly always, the answers to initial questions made further investigation unnecessary. No record was made, and the passenger lost no time.

Observational techniques are not a substitute for all the other techniques we now use to catch would-be terrorists. But they add another layer to transportation security. They are now being used at fewer than one in 10 major U.S. airports. We need to use them everywhere.

Paul Ekman, professor emeritus of psychology

at the University of California at San Francisco,

is a pro bono adviser to the Transportation Security Adminstration's SPOT program.

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