In criminal cases, for example, a change of venue will be permitted if the court feels the defendant cannot receive a fair trial where the court is located. A written declaration upon oath made before an authorized official.An affidavit is a type of verified statement or showing, or containing a verification, meaning it is made under oath on penalty of perjury. What this means to the notary: The law makes certain that an affidavit (notarial language) describing the events of the notarization are. An affidavit is a written statement made under oath that is typically used in legal proceedings. Learn their purpose, when to use, and how to write. An affidavit is the written equivalent of verballygiven court testimony.