Jeffrey Nation was accused of striking Lorenzo Williams, of New Ellenton, in the throat after questioning him.
Nation alleged that Williams attempted to "head-butt" him, and an altercation ended with Williams being arrested.
An investigation determined the former deputy's accusation was untrue. Sheriff Michael Hunt apologized to Williams and to his family, and Nation was fired two days later. Charges were filed by the State Law Enforcement Division.
On Tuesday, Circuit Court Judge Thomas Cooper dropped misconduct charges, according to the Attorney General's Office.