What is it you can't understand? All evidence that we know of at this point "could" have been deliberately placed.
The accused was conveniently preoccupied with the victim's mother and the "preoccupation" was planned earlier in the week. Do I need to go on? Can you comprehend how the game works?
Better yet, why don't you tell us what facts absolutely rule out a frame-up?
That someone can "FIRMLY BELIEVE" that it is a frame up at this point.
Do you "firmly believe" it was a frame up as well?