15-6-13(f). Omitted counterclaim. When a pleader fails to set up a counterclaim through oversight, inadvertence, or excusable neglect, or when justice requires, he may by leave of court set up the counterclaim by amendment.
Source: SD RCP, Rule 13 (f), as adopted by Sup. Ct. Order March 29, 1966, effective July 1, 1966.