How Not To Draft A Probable Cause Affidavit (Zimmerman)
An affidavit shows proper attribution when it explains how the affiant knows each piece of information in the affidavit. That doesn't mean that a proper affidavit can't be based on second-hand or even third-hand or fourth-hand information — it can. But a proper affidavit must explain how each link in the chain gained the information — how everyone knew what they knew — so that the judge can make an intelligent assessment of the sufficiency of the evidence.
For example, a properly attributed affidavit might say "On April 13, 2012, I spoke with Officer Smith, one of the other officers on the case. Officer Smith told me the following: a few hours before he spoke with me, he interviewed witness Jane Doe. Ms. Doe told Officer Smith that she was walking down Main Street when she saw a man she recognized from the neighborhood as Dastardly Dan running out of the bank."
By contrast, a bad affidavit would say "Witnesses indicated that Dastardly Dan was seen running out of the bank." An even worse one says "Dastardly Dan ran out of the bank," and offers nothing to indicate the basis for knowledge.
Even though it was produced under the supervision of a special prosecutor, under circumstances that I'd assume would warrant extreme care, the Zimmerman affidavit falls into the "even worse" category."