They can often tell if a body was killed at the site vs elsewhere.
Let us not forget Karlie was discovered only a short time after she was last seen.
The body found was reasonably "fresh" even though it was likely skeletal.
She died by blunt force iirc....Police can often tell if the body was originally posed (SK) killed suddenly in situ (crumpled in a certain way) or dumped.
In this case, perhaps there were fibres in the wound area that did not come from a forest.
Guessing....but there are ways and means of telling if a body was dead when dumped including insect activity, where it occurs first, what order the decay begins etc.