Saw today that the vehicle actually had a Black Box. They said they know every second of his travel and what he did.
Even without the box, a good collision reconstructionist will know what occurred, speed, the number of rollovers, distances, impact energy etc..Sometimes getting the info from the boxes can be time consuming with legal issues etc..
all later model vehicles have an obd 2 compliant port that can be plugged into and scanned with computers to access any information necessary for crash situations as well as state run emission inspection stations...
and used for reprogramming performance upgrades if so desired...