“That’s why we started rounding up all the Mexicans,” said one former behavior detection officer.

Those results aren’t surprising, according to those involved in the program, because the behavior checklist was, in part, modeled after immigration, border and drug interdiction programs. Drug smugglers and undocumented immigrants often exhibit clear signs of nervousness and confusion, or may be in possession of fraudulent documents.

Nothing in the SPOT records suggests that any of those arrested were associated with terrorist activity.

The $900 million program, Screening of Passengers by Observation Techniques, or SPOT, employs behavior detection officers trained to identify passengers who exhibit behaviors that TSA believes could be linked to would-be terrorists. But in one five-week period at a major international airport in the United States in 2007, the year the program started, only about 4 percent of the passengers who were referred to secondary screening or law enforcement by behavior detection officers were arrested, and nearly 90 percent of those arrests were for being in the country illegally, according to a TSA document obtained by The Intercept.

A controversial Transportation Security Administration program that uses “behavior indicators” to identify potential terrorists is instead primarily targeting undocumented immigrants, according to a document obtained by The Intercept and interviews with current and former government officials.

The detailed 13-page report, taken from the SPOT program’s database, shows the number of referrals made by behavior detection officers, the reason for referral, details about the particular incident, arrests and reasons for arrests, and a brief summary of the incident. The Intercept is redacting the name of the airport involved, the identities of the behavior detection officers and other law enforcement agents involved in the referral or arrest, and passengers’ personal identifying information.

The statistics, though a small snapshot from 2007, appear to buttress repeated criticisms of the program by government auditors and outside groups, which allege that the program is being used to profile passengers based on their race.

The Intercept also interviewed a dozen current and former behavior detection officers, TSA officials, law enforcement agents and other government officials who have been closely involved in the program or monitored it. All of them said the program appears to be designed to target undocumented immigrants and drug smugglers.

Many items on the SPOT checklist are traditional clues for human smugglers and the people they are smuggling, such as “individuals who are seemingly unrelated but display identical dress or luggage.”

One former behavior detection officer described homing in on a “group of Latino guys and gals” wearing brand new outfits that looked like they were bought from a discount chain, like Walmart or JCPenney. “They all looked like they were totally lost and milling around like zombies in fresh clothes and haircuts,” the former officer said.

The behavior indicators point to people who appear confused or nervous because they’ve never been to an airport, may be carrying fake identification or none at all, and are scared about their illegal status being discovered. “You’re essentially making [federal air marshals] profile people,” the former behavior detection officer told The Intercept. “That checklist is ridiculous.”

Still, it has continued, and the TSA has refused to release details on almost every aspect of the program: its behavioral indicators and arrest data, as well as evidence of success in spotting actual terrorists. In March, the American Civil Liberties Union, expressing concerns the program was being used to racially profile passengers, sued the TSA, requesting a variety of documents related to the program.

Last month, The Intercept published TSA’s closely held list of over 90 indicators that behavior detection officers use to identify terrorists. The list, which included “bad body odor,” “whistling” and “excessive grooming,” has been widely ridiculed. The latest document obtained by The Intercept appears to back up previous concerns that the program is aimed at undocumented immigrants more than terrorists.

During a five-week period in 2007, behavior detection officers at this airport identified 429 passengers for secondary screening based on their behavior, after which 47 were referred to law enforcement. Thirty-four of those referrals were suspected undocumented immigrants or those traveling with expired visas.

Instead of terrorists, the officers often found undocumented immigrants who were trying to fly home and were nervous about being caught.

“Passenger spoke no English,” read the notes on several of the referrals.

“Passenger stated that she was in the country illegally and was returning home due [to] lack of work. She also stated that she was nervous due to her illegal status.”

Many of the referrals included statements like, “passenger stated he was nervous due to his illegal status.”

There were 16 arrests over the time frame covered by the report — and none of those arrested were terrorists. Fourteen of those arrested were described as “illegal aliens.” One of the arrests was of an intoxicated passenger who was denied boarding and assaulted an officer, and another person was arrested because suspected drugs and drug paraphernalia were found in his luggage.

Since its start in 2007, the SPOT program has been heavily criticized for its lack of scientific methodology, and even more importantly, its apparent lack of success in identifying would-be terrorists after almost eight years of operation. It’s a pessimistic assessment that even some within TSA share.

“If you’re looking for people who exhibit multiple criteria on the checklist to reach the point of secondary screening or law enforcement referral, you’re just looking for illegal immigrants,” said an aviation security official.

The embattled SPOT program has been the subject of numerous congressional, government and DHS investigations criticizing its effectiveness.

“The checklist misses so many signs of potential danger and really just shows signs of a nervous traveler,” said a current TSA employee involved with the program.

TSA did not respond to, or acknowledge, The Intercept’s multiple requests for comment.

Most of those interviewed supported the idea of deploying roving law enforcement officers at airports to search for potential terrorists, but were critical of nearly every aspect of the current program.

One senior homeland security official said the behavior checklist could work, but TSA’s behavior detection officers have not been properly trained to use it. “My guess is most of them wouldn’t have stopped bin Laden if he walked through their lane,” the official said.