Crash Course describes the science of reconstructing car accidents:
With the right physical evidence, reconstructionists can determine how fast a car was going and whether the driver was braking or swerving in the moments before impact. Sometimes, they are called on to make grimmer determinations — in a truly bad wreck, it can be difficult to tell who was driving the car. In some crashes, the force of impact does all the work: The person with the brake pedal’s pattern etched into the sole of his shoe was probably the driver.Other incidents are trickier to decipher. In a case this spring, a reconstructionist testified that a woman was driving when she and a Hartford businessman careered out of control on Connecticut’s Route 9. The attorney for the woman, on trial for manslaughter, claimed that it was the man who was driving. The lawyer suggested that the woman’s injuries, including a ruptured left breast implant, were consistent not with driving but with performing oral sex on the late businessman when he lost control of the car.
Reconstructionists hold that eyewitnesses are more-or-less useless:
Drivers lie to protect themselves, and given the speed of most accidents, even the memories of honest souls can’t be trusted. Witnesses will swear that a pedestrian was launched 200 yards by a collision — a feat that could only be accomplished if the offending vehicle were doing something like Mach 3. They will claim a black car was white, or a white car was red. Once, three cops commenting on the same accident told Rich respectively that the conditions were wet, dry, and icy.