Business Week: How Not to Catch a Terrorist ... They’re also sizing up passengers for signs of suspicious behavior, such as excess anxiety or sweating. Known as the Screening Passengers by Observation Technique, or Spot, the program was put in place to nab terrorists and is now used at roughly a third of U.S. airports. After nine years, government studies show that it’s turned out to be an effective tool for sniffing out alleged criminals—just not the ones it was intended to catch. So amid criticism from civil liberties advocates, the U.S. Department of Homeland Security has brought in consultants to revisit the program. According to the U.S. Government Accountability Office, there’s no evidence that Spot has caught a single terrorist. Of 353 arrests from November 2010 to April 2012, 68 percent were for immigration offenses, drug charges, or outstanding criminal warrants. (TSA agents can’t make arrests; they refer suspects to law enforcement.) From 2004 through 2008, according to the GAO, none of the 1,083 arrests resulting from TSA referrals resultedin terrorism charges.