Pauper’s oath refers to a sworn statement or oath by a person which declares that s/he is completely a destitute or a pauper. Usually, prisoners filing legal actions use a pauper's oath. In a civil trial, it refers to an affidavit required of an indigent litigant to be exempted from court fees or costs. Whereas, in a criminal trial, it is used to qualify for the assistance of a counsel who represents the accused and the expense is met by the government.
According 18 U.S.C.S. § 3569 (repealed), a convict can secure his/her release from prison before paying a committed fine by taking the pauper's oath. [United States v. Estrada, 878 F.2d 823 (5th Cir. Tex. 1989)]