Started Tulane Law School in 1957 upon discharge from the Active Duty Air Force. During school he worked full time at the Whitney National Bank at night in the Accounting Department and flew with the Air Force Reserves at Alvin Callendar Naval Air Station. Upon completion of law school, he worked full time for the Federal Aviation Agency as an Air Traffic Controller in the New Orleans Center from 1960 until 1963 while he was starting a general practice of law. John was appointed Assistant District Attorney in 1966 in Jefferson Parish, Louisiana and became Executive Assistant in 1968. Later, Mr. Mamoulides was appointed District Attorney upon the retirement of the previous District Attorney. In August 1972 he was elected for his first term as District Attorney and was reelected in 1978, 1984, and 1990. John retired from the office of District Attorney in 1996, after serving 30 years and was then appointed by David M. Barrett as a Legal Consultant to the Office of the Independent Counsel.