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.A written declaration upon oath made before an authorized official. After filling out your forms, file them with the justice court where your case was filed. An affidavit is a written statement that you swear is true and that may be used as evidence in a court of law. A warrant may be issued upon an affidavit or sworn oral testimony. , "A wild animal is there for the taking. Affidavits are filed in many scenarios, such as in the case of proving residency to meet a residency requirement.