Officer Ana Paz slowly scanned the airport terminal, studying faces, luggage and movements, her right hand fixed on the semiautomatic rifle strapped to her chest. She spotted someone suspicious-looking.

The man looked angry, she thought.

And he probably was.

He was waiting for his wife to get out of the restroom at Miami International Airport.

Authorities at about a dozen airports around the country are using "behavior pattern recognition" — monitoring passengers' actions and expressions in hopes of spotting terrorists.

Airports tend to have lots of people who look angry, tense or furtive. But security officials here are so impressed with behavior pattern recognition techniques — which they say can distinguish a nervous traveler from a dangerous one — that they say they plan to expand their use more widely in Miami than at any other U.S. airport.

If officials have their way, all 35,000 of the airport's workers — including janitors, skycaps, even Starbucks coffee servers — will be trained to watch travelers for suspicious movements. At other airports, such training is generally limited to security and law enforcement officers.

"If you had 35,000 pairs of eyes observing suspicious behavior, that's a strong layer of security," said Greg Chin, a spokesman at Miami International Airport, where officials began training senior airport managers Thursday.

The federal Transportation Security Administration says officers at about a dozen airports are using behavior screening at checkpoints — though they wouldn't say which ones — and they expect to expand the program. In Miami, airport police, who are separate from TSA officers, are also using the methods.

Ann Davis, a TSA spokeswoman in Boston, where the agency launched its behavior screening effort shortly after Sept. 11, said the program has yielded about 95 arrests for fraudulent documents, money and drug smuggling, and other offenses. But she said it is unclear whether any of the arrests were connected to terrorism.

"It has been successful in catching bad guys, but not bad terrorist guys," said Richard Bloom, a dean who directs terrorism and security studies at Embry-Riddle Aeronautical University in Prescott, Ariz.

But such efforts are necessary because officers and technology are limited in what they can do, said Rafi Ron, the former security director at Ben-Gurion International Airport outside Tel Aviv, Israel. He now heads a company called New Age Security Solutions, which is working with officials here to train them in behavior recognition techniques.

Ron pointed to the example of would-be shoe bomber Richard Reid, who exploited lapses in security screening but whose behavior was ultimately noticed by fellow passengers.

He said most terrorists don't have the "tremendous personal skills" necessary to escape detection.

Law enforcement authorities trained in behavior recognition are careful not to reveal exactly what would pique their interest. But on a patrol with Paz, it was clear it could be any number of things — someone rifling through a trash can, an unattended bag, a young man sitting on the floor alone, or a seemingly unhappy face.

"When you scan a crowd, you're looking for what's unusual," said Paz, a 25-year veteran of the Miami-Dade Police Department.

Such efforts have been in place at Ben-Gurion Airport for years, and they were brought to American airports after the Sept. 11 attacks. But Bloom said good security officers have long used behavior screening of one sort or another.

The American Civil Liberties Union filed a lawsuit two years ago challenging the use of behavior recognition at Logan Airport in Boston, claiming it "effectively condones and encourages" racial and ethnic profiling.

In Miami, Ron told the roughly 70 training participants that behavior recognition is not about racial profiling, and he pronounced such screening ineffective. He noted that the two terrorist attacks carried out at Ben-Gurion were by people Israelis would not necessarily have suspected — Japanese and Germans.

Something terrorists do typically share, he said, is an uneasiness about what they are about to do.

"If you're carrying a device on you or in your bag, if you believe you're going to heaven as these people do," Ron said, "you behave differently."

Separately, a polygraph-like device that can supposedly identify potential terrorists in as little as three minutes from their biometric responses — skin, blood volume and voice — to key questions was tested this summer at McGhee Tyson Airport near Knoxville, Tenn.

TSA is interested in the $200,000-per-unit Cognito scanners, which are being developed by an Israeli company, Suspect Detection Systems, whose principals include the former deputy head of Mossad, Israel's elite intelligence unit.

The test results have not been released, but the company says units are scheduled to be deployed later this year in some airports in Israel.

"We do not check general nervousness," said Shabtai Shoval, the company's chief executive. "Our system can identify only people that are terrorists or criminals. Nervous passengers will not be detected."