Richard Lamoureux, a collision reconstruction expert from DFA Engineering Services Inc., presented his report to court Tuesday, deconstructing the incident as four collisions, not one. Lamoureux said his report was based on a combination of video from the bus, data that was downloaded from the bus by investigators and police reports. He said he did not interview Diallo. Court was shown video from the back of the bus that showed a stop request sign was lit at 3:49 p.m., a little more than a minute before the crash. Lamoureux said the double-decker's movement was gradual and resembled a lane change to do a stop at Westboro station.