You. you would look for those cues of the gray sweatshirt and green vest, but you may not have those on the way out. you would look to other things they re wearing, shoes, pants, the backpack, that can t be changed quite so easily. and those are the indicators that you would look for on potential exit videos. so we will identify the make and model of the shoes he s wearing and the backpack. you can t imagine the level of detail that the analysts and investigators go to in really tying that stuff down. and juliette kayyem, the expertise is critically important in the sense that it is so crowded. there are so many people. the new york city subway system, the most crowded subway system of all.