Complex sentence: The federal courthouse was the site of the 1966--1967 trial of suspects in the murder of Chaney and two other activists; it was the first time an all-white jury convicted a white official of a civil rights killing.
Split into simpler sentences: The federal courthouse was the site of the 1966--1967 trial of suspects in the murder of Chaney and two other activists. For the first time, an all-white jury convicted a white official of a civil rights killing.