up upsidedown in a pond. >> reporter: it wasn't the floor mats, those were the in trunk right where hardy put them after receiving the recall notice weeks earlier. it wasn't a seizure, although hardy was on medication, the autopsy ruled that out. so what really happened? what if the car could talk? essentially it can. most vehicles have what's commonly called a black box known as an event data recorder or edr. >> this those kinds of accidents, edr will be invaluable. shawn dennis reconstructs car accidents for law firms and insurance companies. >> it's all the way down. >> reporter: the black box is tied into the air bag system and records two to three seconds of pre-crash data, throttles accelerators, seat belts. >> we see 2.3 seconds before the