The FBI is also using gait analysis, a technique used to identify someone by the way the person walks, hoping it will lead to a suspect. Agents have released surveillance video to see if someone in the public might recognize the suspect from the way he or she moves.
Dr. Mike Nirenberg wrote a textbook on gait analysis, and he reviewed the FBI video with NPR. "Look at how close their feet are to each other. … So that is a narrow base of gait," he said, watching the suspect. "Immediately what you notice is the arm swing of the person on that left arm. … There isn't a lot of rotation in the upper half of their body, their torso."