through logical deduction we can say that LE did NOT take the screen door for:
*prints (they already lifted prints and the doors been cleaned).
*to show how it slammed shut (the entire door frame would have been taken for this).
*trace evidence such as dna (evidence would have been extracted & tested while in police custody)
which leaves:
*prints of someone who has recently been there and used that door (someone they didn't have enough evidence to subpoena or get a court order for?)*the door itself is evidence, such as scrapings or marks showing that a brick had been used many times to hold it open.
If anyone can think of more, please add to the list.