An affidavit is a legal document that is used to provide written evidence or a statement of facts under oath. An affidavit is a statement made under oath, claiming that a fact or set of facts is true to the best of the "affiant's" knowledge.A written statement that someone makes after promising officially to tell the truth. An affidavit can be used as proof in a law court. Affidavit in Support of Attorney Fees - ASAF (CIV). ASDJ. It also might mean you lose the case, depending on the motion that was filed. The clerk will fill it out for you. Clark's Cross Cl. Resp. J), two Appellant affidavits (Exh.