>> investigators are out with a report declaring a huge government expenditure a failure. it involves a tsa behavior detection strategy at u.s. airports where certain officers would be trained to look in effect for likely terrorists. the program has cost almost a billion dollars. the investigators studied the data and conclude there is no evidence it does any good. our report tonight from nbc's tom costello. sn .

>> reporter: it's a tactic borrowed from the israelis. scanning the crowd for anyone who doesn't seem to fit in. nervous, jumpy, hostile, perhaps wearing a big coat on a warm day. then talking to them to learn their motives. a new gao report calls for cutting funding to the tsa program because there is no evidence behavior detection works and the ability to accurately identify deceptive behavior based on behavioral indicators is the same as or slightly better than chance. tomorrow the tsa chief faces questioning on capitol hill .

>> how is this a value to the average american traveling through the airports? how will it make them safer and therefore is it worth the money we are investing in it?

>> reporter: the tsa has 3,000 screeners dedicated to behavior detection screening nearly 2 million people a day. already credited with stopping police impersonators, drug couriers and potential terrorists. a behavior specialist was among those wounded in the l.a.x. shooting rampage two weeks ago. the tsa says behavior detection is vital to the layered approach to deter, detect and disrupt individual who is pose a threat. in israel behavior recognition is critical and the program should be expanded.

>> here the program should include law enforcement at the airport and beyond that the employees, all the airport community wherever they are.

>> reporter: behavior detection is used around the world. tonight the question is whether this core tsa program has been worth a billion dollars. tom costello, nbc news, miami.