Jan. 17--WARWICK -- Since 2004, security officials at T.F. Green Airport have tried to spot dangerous passengers by a pulsing cartoid artery, how much they sweat, blink, and behave in ways that might indicate an anxiety that stems from something more sinister than a fear of flying.
The federal Transportation Security Administration is looking for passengers who have their stress hormones up and running because they intend to attack the air transportation system.
Green was among the first three airports in the nation to test "behavior detection techniques" -- a list of "tells" that federal officials think may help them to identify terrorists.
Joseph S. Salter, the federal security director assigned to Green, said "a significant number" of TSA's 250 officers at Green have been trained in the program officially known as "Screening Passengers by Observational Techniques," or SPOT.
So have members of the Rhode Island Airport Police Department, the state employees that TSA calls upon to speak with passengers who score high on the federal SPOT scale.
TSA will not say how many airports it added to the SPOT program after introducing it in Boston in 2002 and expanding it to Warwick and Portland, Maine, two years later.
Ann Davis, a TSA spokeswoman in Boston, said SPOT is in use full time at "a handful" of airports across the country and that a number of others took part in a two-week trial last month.
Some civil libertarians challenge the techniques as subjective, racially biased, probably ineffective at spotting a trained terrorist, and a waste of resources that could enhance security if used elsewhere.
TSA, an arm of the U.S. Department of Homeland Security, still considers SPOT an experimental program, Davis said. The agency expects to decide this year whether it works and should be put into practice at all airports.
In an interview last week, Salter endorsed the program, saying, "I personally see the value of it" at Green.
Salter, 60, is a former police officer and detective for the Port Authority of New York and New Jersey, and counted as "personal friends of mine" 25 of the 37 Port Authority employees killed in the 9/11 attack on the World Trade Center.
He was assigned to JFK, Newark and LaGuardia airports from 1973 to 1991, retiring as a detective sergeant.
He called the SPOT criteria an attempt to codify behaviors that every good beat cop practices instinctively.
"I cut my teeth on this stuff," he said.
TSA will not reveal the behaviors on the SPOT scorecard, but Salter said, "The public has a right to know what's going on and we have a duty to share with them the fact that there are things being done in their best interest. I think this is a worthwhile program and I have no problem saying it."
As one part of the array of security measures in place at Green, SPOT presents terrorists with one more obstacle to a successful attack, Salter said.
"Those people are opportunists," he said. "They'll seek a softer target," though no one can say whether Green was ever scouted by terrorists and abandoned as a potential target because of SPOT or any other aspect of its security program.
Salter said he was confident in the deterrent effect, but "how do you prove that you've deterred somebody?"
"We're looking for anything and everything" that might pose a threat, he said.