There was something about Alex Sadak; at Oakland International Airport recently, he was sweating - seemingly on edge. Nearby, two screeners took notice and approached him to make small talk.
"To be honest, I actually said good morning to him. He looked at me - I don't know why they zoned in on me," said Sadak.
They are not your normal screeners. Daryl Prince and Donald Richardson are a team; specially-trained behavior detection officers to prevent passengers with criminal intent from getting on a plane.
"It's a science and an art form put together," said Richardson.
"We just observe behavior for involuntary physical and physiological things they might do when anybody has a fear of being discovered," said Prince.
"It ranges from clothing to facial expression," said UCSF psychologist Paul Ekman.
Ekman helped the Transportation Security Administration develop its behavior detection program. The author of "Emotions Revealed" says had these officers been on the job on September 11th - they would have stopped the hijackers.
"They showed a whole variety of signs of impatience, anger," said Ekman.
Dr. Ekman trains the TSA officers to discern common emotions.
"In anger the eyes glare while they're relaxed in disgust," said Ekman.
When these TSA officers spot hidden emotion in combination with several other specific behaviors on the list, they'll approach the passenger, talk with them, and put them through additional screening. Usually, that clears things up. As in Alex's case, he had been drinking the night before and was admittedly hung-over.
The TSA says most people arrested under this program had immigration issues, forged ID's, or outstanding warrants - in other words, a reason to be nervous.
In Orlando last month, behavior detection officers uncovered a man whom they say was attempting to bring bomb-making components onboard a flight. And since the program started at Oakland two months ago, three people have been arrested for drugs. But despite these arrests, some civil liberties advocates say this program is deeply flawed. First, because lots of people are agitated at airports, so lots of false alarms. And second:
"It could lead to a very bad path where we're actually profiling people of certain races and ethnicities," said Tim Sparapani, ACLU.
The two men investigated while we were there were both minorities - one of them a pastor from Stockton.
"Not a problem, better to be safe than sorry," said the pastor from Stockton.
The TSA won't release exact numbers, but officials tell us the 40,000 passengers they've targeted under the program have been across the board in gender, race and age.
"Somewhere out there the needle in the haystack is a bad guy. If our behavior detection officer's give us better odds of finding that needle, we're going to use every tool we can while protecting the rights and privacy of passengers," Nico Melendez, TSA spokesman.
Right now, there are more than a-thousand of these trained officers on the job at 100 of the nation's biggest airports.