The supposed "exculpatory evidence" is there. They are going to claim that the deputy looked in August and didn't see any such bag or white thing or skull. They are going to claim that DC looked in November and did not see any such bag or thing. Etc. Although we can debate the merits of such argument--this is the evidence they are relying
upon.
If that is the evidence the defense is relying on...Casey better start making a list of her pen-pals now. She is definitely up that proverbial creek...