>> reporter: well, i can tell you that the national guard, victor, is on standby in case things get more chaotic tonight. we know that police officers are working 12-hour shifts, some officers cancelled their personal days off. and, obviously, the city is basically bracing for more chaos that could happen tonight. victor? >> all right, dan simon there for us in st. louis. dan, thank you so much. well, the dramatic dash cam video captured the moment that officer shot and killed smith. >> the video at the center of that high profile murder trial when prosecutors argued stockley planted evidence. as cnn's jean casarez reports, though, the judge just didn't agree. >> reporter: a high speed chase caught on police dash cam. two st. louis police officers pursuing a 24-year-old black man, anthony lamar smith, in december 2011. prosecutors claim officer jason