Thanks, Dandan.
You reminded me that I am so focused on Alanna falling out of a red truck, that I haven't explored that other ways her body could have fallen out of, or off a vehicle (and also that the red truck could be a red herring)
Your strap to the roof scenario is plausable.
Thanks!
The more I think about it, the more plausible it sounds...
Since the beginning I did think the body was dumped there intentionally, but now i don't think it was. If her body was intentionally dumped there near the curb, the perp would have to stop at the intersection, check if no one is around, lean over, open the door, then make sure the body was pushed out, all from the drivers seat. It just seems too risky having to do that at an intersection in broad daylight. A second perp sitting in the passenger seat would have made it easier I guess though.
But with the tarp and body being secured on the roof, it sounds a lot more plausible. With regards to the question about would the perp have put the body on the roof in broad daylight then who knows. But maybe they have a garage so the daylight issue wouldn't have been a problem in getting it on the roof. Also there is more chance of evidence being left if the body was in the boot or in the vehicle and it would be harder to remove any evidence from inside the boot too.
It really does make sense as to why LE took all different restraints from the family home imo. One of these restraints came loose or broke, resulting in the tarp falling off as he went around the corner. He panicked and took off leaving the body wrapped in the tarp in the road.