The problem is this wasnt a normal case
there were so many crazy people and stories involved THAT TOOK THE STAND.
You have a scientist from Mars that wants to put leashes on flies, and in his spare time he goes in the woods with coat hangers looking for hidden graves.... THAT TESTIFIED FOR THE STATE
Obviously Casey is shady as shit and PROBABLY had SOMETHING to do with the death of Caylee, but how can you possibly get the facts right when you have liars left and right telling you the story?
Yup, and that's trial lawyering 101. If you can't put a story together that is believeable, you have no chance to convict.