The other thing is, the footprints would be entirely different depending on which direction the car was facing. If facing east, entering the car would be fairly simple with all the prints within a roughly 60 degree angle from the car, basically the area between the rear fender and the open door. If the car was parked heading west, then the footprints would cover an area about 150 degrees alongside the car because they would have to go around an open car door. The difference would be rather significant to an expert inspecting the prints.
If the former were true, it would seem to support DRs story of the car turning around in his yard, and after the kidnapping. It could also explain why Aaron and Trevor didn't see a car - due to the headlights moving away from them.
On the other hand, if indeed the kidnapper was in that car, and was there was an afternoon car as DR says, I have to wonder why the kidnapper would not have turned around before the kidnapping? Assuming DR is right, the kidnapper had to have known that he was in a driveway, and it seems extremely risky for him to take the time afterward to turn around, especially knowing he would have to drive another 1/2 mile after turning around, to get off the dead end road and back to St Joseph.