the oncoming lane traveled by the secret service. it was clear the skid marks would be a critical clue. the mait investigators then interviewed eyewitnesses, one of whom was driving behind the secret service cars. according to her, the agents did nothing wrong. >> they were relaxed, taking their time, driving along at a reasonable speed for the area and the terrain. >> after gathering all the evidence, the mait investigators began the hard work of reconstructing what caused the accident. >> what i'm doing here is called motion analysis. i'm using the scaled physical evidence and the scaled vehicles to try to determine how the vehicles were moving during particular phases of the collision. >> the motion analysis provided