Upon graduating from law school and passing the New York bar exam, Dunnaville began work for then United States Attorney for the Southern Distict of New York (and later New York City District Attorney) Robert Morganthau, whom he considers his most important mentor.
Upon graduating from law school and passing the New York bar exam, Dunnaville became the first African American to work for the Internal Revenue Service. In 1961 he began work for then United States Attorney for the Southern Distict of New York (and later New York City District Attorney) Robert Morganthau, whom he considers his most important mentor.