PORTLAND – Airports in Bangor and Portland are among the four in New England that are employing security officers who use behavior detection techniques to identify people who are acting suspicious.

The federal Transportation Security Administration implemented its pilot program for behavior detection – the practice of analyzing people’s actions to determine whether they have something to hide – at Boston’s Logan International Airport in 2002.

It was expanded to T.F. Green Airport in Rhode Island and Portland International Jetport about a year ago, and to Bangor International Airport about two months ago.

The TSA is facing opposition from the American Civil Liberties Union, which filed a lawsuit in Massachusetts last year claiming behavior detection can be easily abused because TSA officers have to guess who is suspicious, leading to racial profiling.

Supporters say behavior detection is a valuable tool in fighting terrorism and has been used for years around the world. Screeners, they say, can be trained to look at the way people act and talk outside the context of their race.

At Logan airport, the program is based on an Israeli model, said George Naccara, federal security director at Logan. Screeners are trained to look for telltale signs that someone is too nervous for the circumstances.

“They are trained to look for stress, fear or some sort of deception,” Naccara said. “They identify certain characteristics and pass the information on to local law enforcement.”

The security personnel who are trained in behavior detection have no responsibilities other than watching travelers and engaging them in conversation. They don’t search luggage or sweep people with a magnetic wand.

Shenna Bellows, executive director of the Maine Civil Liberties Union, said screeners could confuse cultural differences with suspicious behavior, making their judgments too subjective.

Behavior detection is popular at airports because it is inexpensive, she said.

“We are not confident that it can be done successfully, because of racial profiling,” she said.

Behavior recognition analysts are doing what police officers have always done, said William McClaran, a former Portland police chief who teaches law enforcement at Southern Maine Community College.

Everyone shows signs of nervousness when put in a stressful situation, such as getting pulled over for a speeding ticket, McClaran said.

“But these guys are looking at situations when there are no stressors apparent but people exhibit signs of nervousness anyway,” he said. “Eyes darting about, arteries in the neck trembling, something that indicates something out of the ordinary.”