That will be a possible argument.Remember, it's proof "beyond a reasonable doubt" (generally considered to be >90%). Not "more probably than not" (51%). That's a high bar. Anyway, I'm not claiming to support any of these ideas, just playing devil's advocate!
What he said in the initial interview with police will be telling. Did he say he was unaware of striking anything? Or of striking a person?
Tough to claim he was unaware of striking anything when you repair your car.
Also, as I recall, the police report mentioned the person struck was on the hood of the car for about 1000 feet! If that is the case, that is 12 seconds at 60mph (I don't know how fast the car was going). I just can't see this going well for the guy.