John Foster DeRosier, 78, longtime District Attorney for Calcasieu Parish, died Thursday morning. John DeRosier attended undergraduate school at the University of Southwest Louisiana in Lafayette, La., and entered Louisiana State University Law School in 1967. As a Lake Charles resident of 50 years, John DeRosier had a law practice that focused on civil litigation, personal injury, and criminal law until his election as District Attorney. John DeRosier took the oath of office for Calcasieu Parish District Attorney on Dec. 20, 2005, and was re-elected to additional six-year terms in 2008 and 2014, serving as District Attorney for 15 years. He was preceded in death by his first wife, Karen McBurney DeRosier; his parents, Paul and Helen Miller DeRosier; two sisters, Helena Head and Dolores “Tiki” DeRosier; two brothers, Paulie DeRosier and Francis Joseph DeRosier.