Complex sentence: Frierson said that the rumored culprit came from a well-known, prominent white family, and had served on the initial coroner's inquest jury which had recommended that Stinney be prosecuted.
Split into simpler sentences: Frierson said that the rumored culprit came from a well-known, prominent white family. A member or members of that family had served on the initial coroner's inquest jury which had recommended that Stinney be prosecuted.