RSBM
The ME does not know how the vehicle impacted John, so how can she make any determination? She's not an accident reconstructionist, and the only information she has is broken taillight plastic, not crushed-in car bodywork. She doesn't know that his arm measures up exactly to the taillight because she didn't inspect the car or do those measurements. She doesn't know his eyelid is the same height as the wing. She doesn't know if he could be hit at such an angle in a split second that he could be spun away from the car, causing no lower body injuries.
She couldn't determine how his arm injuries occurred because she's not a biomechanic to determine speeds, forces and properties of materials, and even if she'd said it could be consistent with a car side-swipe, she wouldn't be able to determine whether that was accident or homicide - that is for a jury to decide if no one is forthcoming about knowing he was there, or deliberately or recklessly driving at speed in reverse towards him in the dark. An example of accidental collision could be driving carefully but braking sharply and skidding on ice.
This is the way I see it. If my elbow is hit by a lump of metal traveling at say 20 mph, I would certainly expect bruising and bone fracture. If my elbow is hit by a sheet of frigid plastic, which is travelling at the same speed, and my elbow shatters that plastic for a split-second, I might not expect a bruise or fractured bone, but I would expect skin damage. Because it's broken through the plastic which immediately reduces the force/impact on my bone. IMO bone is stronger than frigid plastic, but it's not stronger than a lump of metal, and it's not going to break the metal.
ARCCA didn't prove that his arm bones would break by breaking through plastic, or bruise him, so they can't give that opinion IMO. They weren't interested, but it's their claim to prove, if that's what they contend. They used a dummy arm to show taillight damage, not arm damage. An arm which is not human bone and flesh, an arm which wouldn't react and bend like a human arm with muscles and ligaments attached to a body which pulls the arm away as the body is spun away and transfers the force to the body, IMO. The commonwealth doesn't have to prove his arm wouldn't break, they can and did certainly show statistics and car accident victims whose bones didn't break, but those circumstances also aren't identical to this collision, and there are unknown variables that cannot be demonstrated without hundreds of human volunteers in hundreds of different positions at hundreds of different speeds and temperatures. There was a man, a sole survivor, who just walked away from a plane crash in the news.
It's the totality of the evidence that the commonwealth has, the car, the scene, the body, the clothing, the DNA, the phone, the defendant, the weather, which proves the collision and the cause of John's injuries and death. Not the ME.
MOO