antithetarius

from Bouvier's Law Dictionary, Revised 6th Ed (1856)
ANTITHETARIUS, old English law. The name given to a man who endeavors to
discharge himself of the crime of which he is accused, by retorting the
charge on the accuser. He differs from an approver (q, v.) in this, that the
latter does not charge the accuser, but others. Jacob's Law Dict.
    

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