S.C. Code Ann. § 19-11-20

Notwithstanding the provisions of SECTION 19-11-10, no party to an action or proceeding, no person who has a legal or equitable interest which may be affected by the event of the action or proceeding, no person who, previous to such examination, has had such an interest, however the same may have been transferred or come to the party to the action or proceeding, and no assignor of anything in controversy in the action shall be examined in regard to any transaction or communication between such witness and a person at the time of such examination deceased, insane or lunatic as a witness against a party then prosecuting or defending the action as executor, administrator, heir-at-law, next of kin, assignee, legatee, devisee or survivor of such deceased person or as assignee or committee of such insane person or lunatic, when such examination or any judgment or determination in such action or proceeding can in any manner affect the interest of such witness or the interest previously owned or represented by him. But when such executor, administrator, heir-at-law, next of kin, assignee, legatee, devisee, survivor or committee shall be examined on his own behalf in regard to such transaction or communication or when testimony of such deceased or insane person or lunatic in regard to such transaction or communication, however the same may have been perpetuated or made competent, shall be given in evidence on the trial or hearing in behalf of such executor, administrator, heir-at-law, next of kin, assignee, legatee, devisee, survivor or committee, then all other persons not otherwise rendered incompetent shall be made competent witnesses in relation to such transaction or communication on said trial or hearing.