The man in the cheap brown jacket slumped in line, staring at the ground. His hands were fidgety, reaching repeatedly into his jacket pocket, or patting it from the outside. A momentary look of anguish, just a fraction of a second or so, occasionally flashed across his face: the inner corners of his eyebrows would go up, so that his brows sloped down from the center of his forehead; his cheeks would rise; and the corners of his lips would pull down slightly. He was exhibiting what I call a micro-expression, a sign of an emotion being concealed.
The question was: What was he concealing? And why?
To the behavior-detection officers I was with at Boston's Logan International Airport, his combination of mannerisms - the micro-expression, the slumped posture, the pocket-patting - raised a red flag. They called a state police officer, who asked the man the purpose of his travel. It turned out that he was going to the funeral of his brother, who had died unexpectedly. That was the reason for the bowed head. The frequent chest-patting was to reassure himself that he had his boarding pass. The micro-expression was an attempt to conceal his grief.
The man was not a terrorist, just an innocent traveler carrying some extra emotional baggage that day. So why single him out for questioning because of a fleeting expression and a sad-sack posture?
Critics of the controversial new security program I was evaluating - known as SPOT, for Screening Passengers by Observational Techniques - have said that it is an unnecessary invasion of privacy, based on an untested method of observation, that is unlikely to yield much in the way of red-handed terrorists set on blowing up a plane or flying it into a building, but would violate fliers' civil rights.
I disagree. I've participated in four decades' worth of research into deception and demeanor, and I know researchers have amassed enough knowledge about how someone who is lying looks and behaves that it would be negligent not to use it in the search for terrorists. Along with luggage checks, radar screening and the rest of our security arsenal, observational techniques can help reduce risks - and potentially prevent another deadly assault like the attacks of Sept. 11, 2001.
Much has been said about the Sept. 11 hijackers' unusual behavior in the days before they boarded their ill-fated flights. Several were repeatedly questioned, but no one recognized their lies. An airport screener later said he had been suspicious of one because of his strange demeanor that day. But the screener had no training that would have given him the confidence to act on his suspicions.
The hijackers' lies - to visa interviewers and airport check-in workers - succeeded largely because airport personnel weren't taught how to spot liars. The people who might have saved the lives of many Americans were needlessly handicapped.
Imagine if that screener had been taught to discern the signs of deception in a person's facial expressions, voice, body language and gestures, making him confident enough to report the hijacker's behavior. SPOT, which the Transportation Security Administration introduced this year at 14 U.S. airports, is the first attempt at using observational techniques as part of our security approach, and it is promising. Preliminary findings show that the overwhelming number of those detained for further investigation were intending to commit or had committed some kind of wrongdoing: They were wanted criminals, drug smugglers, money smugglers, illegal immigrants - and, yes, a few were suspected terrorists.