184.—Suppletory oath. In the civil and ecclesiastical law. The testimony of a single witness to a fact is called ‘half-proof,” on which no sentence can be founded; in order to supply the other half of proof, the party himself (plaintiff or defendant) is admitted to be examined in his own behalf, and the oath administered to him for that purpose is called the “suppletory oath,” because it suphlice the necessary quantum of proof on which to found the sentence. 3 Bl. Comm. 370. This term, although without application in American law in its original sense, is sometimes used as a designation of a party’s oath required to be taken in authentication or support of some piece of documentary evidence which he offers, for example, his books of account.—Voluntary oath. Such as a person may take in extrajudicial matters, and not regularly in a court of justice, or before an officer invested with authority to administer the same. Brown.