When asked whether he had been to New York recently, he "became quiet and started to shake", according to an affidavit. A written statement that someone makes after promising officially to tell the truth.An affidavit can be used as proof in a law court. 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 written statement which you swear is true and which may be used as evidence in a court of law. Affidavit definition: A written declaration made under oath before a notary public or other authorized officer. An affidavit is a written statement that you swear is true and that may be used as evidence in a court of law. 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. In a nutshell, an affidavit is a sworn statement that is documented in writing. Congress and the states continue to legislate new rights and remedies; the courts continue to define and redefine legal terms; the states are increasingly.