Ohio Rev. Code § 6131.61: Oath of witnesses.

In any hearing provided for in sections 6131.01 to 6131.64, inclusive, of the Revised Code, before a board of county commissioners, at which testimony to determine any fact is to be received, an oath as in trials in the court of common pleas shall be administered to all witnesses before they testify. Such oath may be administered by the president of the board.