Defensor matrimonii an officer of the Roman Church in every diocese, whose duty it is, in cases where a marriage is claimed to be null, to search for and produce the proofs of its validity, and to follow the case into any court to which it may be carried by appeal, with the right of originating such an appeal himself in cases where, through some defect in the proceedings or in the testimony, a verdict of nullification has been granted upon insufficient grounds. The office was instituted by Benedict XIV by his bulls of Aug. 26, 1741, and Nov. 3, 1741 (Bullar. Magn. tom. xvi, p. 41, 48).