Triumviri capitales or treviri or tresviri
TRIUMVIRI CAPITALES or TREVIRI or TRESVIRI, Rom, civ. law. Officers who had charge of the prison, through whose intervention punishments were inflicted. Sallust in Catalin. They had eight lictors to execute their orders. Vicat, ad voc.
A Law Dictionary, Adapted to the Constitution and Laws of the United States. By John Bouvier. Published 1856.