Wall Street Journal: “The people-based program — called Screening Passengers by Observation Technique, or SPOT — began undergoing tests at Boston’s Logan Airport after 9/11 and has expanded to about a dozen airports. Trained teams watch travelers in security lines and elsewhere. They look for obvious things like someone wearing a heavy coat on a hot day, but also for subtle signs like vocal timbre, gestures and tiny facial movements that indicate someone is trying to disguise an emotion. TSA officers observe passengers while consulting a list of more than 30 questionable behaviors, each of which has a numerical score. If someone scores high enough, an officer approaches the person and asks a few questions.”