A written declaration upon oath made before an authorized official. Introduction. The complicated nature of various terms and phrases relating to bail and pretrial release or detention can sometimes lead to confusion.An affidavit is a sworn statement of fact that can be used in a variety of legal proceedings, from bankruptcy cases to family and civil litigation matters. An affidavit is a sworn statement a person makes before a notary or officer of the court outside of the court asserting that certain facts are true.