S.C. Code Ann. § 16-3-460: Pleading in bar by State's witness to subsequent indictment.

In case any such person so used as a witness in behalf of the State in any prosecution for fighting a duel or for being concerned therein shall afterwards be indicted for the same offense, the fact of his having been used as a witness in the former prosecution for the same offense may be pleaded in bar to such subsequent indictment and, on proof thereof by competent evidence, such person shall be thereof acquitted and discharged.