Royce Knox McMahon was born in Columbia, South Carolina to the late Royce Edward McMahon, a Columbia Police Sergeant and Detective, and Lena Elizabeth Knox McMahon.

Judge McMahon has four children (one deceased) and three grandchildren.

Judge McMahon received his B.A. and J.D. from USC. He is a former Columbia Police Officer, USC Police Officer, Lexington County Sheriff’s Deputy, Assistant Solicitor, and private practitioner.