one is pulseless and unresponsi unresponsive. >> reporter: it looked like an accident, but prosecutors accused one of killing her sister intentionally by driving them both off a cliff. >> everyone standing around saw her take the explorer off the cliff with her sister beside her, plummeting them to a death. she survives with her air bag and her safety belt while her sister dies a horrible death. >> reporter: authorities said the car's data recorder indicated she was accelerating right before the crash and never applied the brakes. a key point of dispute if this goes to trial. >> the defense is clearly going to be they were in an argument. she got distracted by her sister who was attacking her in the car, and the car went off the cliff. this is a real and viable defense. >> reporter: eyewitnesss say they saw the blonds physically fighting in the vehicle just before it happened. >> i could see a pair of hands yanking on the driver's head,s and she was arguing with the person. >> reporter: the ordeal seeming like a scene ripped right out of magnum p.i. but hours ago after hearing testimon