CNN The Situation Room September 25, 2013 21:51:00
Nervousness and physiological reaction, as well as potential concealment of weapons. >> reporter: and more subtle ticks in behavior. >> from the tiniest expression in the face to the way somebody walks or carries themselves, how they're looking at another person or an area. >> reporter: but their cutting-edge approach goes further. twice a month they hold lockdown drills for employees and customers. >> announcer: attention, this is a drill. >> reporter: customers are told to shelter in the back rooms of the nearest store. there are security checks for vehicles coming in with merchandise. rosin...