He was a Queen's Counsel who served as the Solicitor General for New South Wales (1974–78), and held the rank of colonel in the Australian Army Legal Corps.
The RAAF Air Board Citation reads in part, "Flight Lieutenant Marr has proved himself to be a consistently conscientious, efficient and reliable captain of Catalina Aircraft, who can always be depended upon to carry out his task regardless of difficulty.
He retired early from this appointment in March 1978,[4] and returned to private practice at the Bar, where he formed and headed a floor of Barristers in Garfield Barwick Chambers.
[citation needed] In 1998, Marr was awarded a Medal of the Order of Australia in recognition of his services to veterans' affairs and the Christian Brothers College, Waverley.
Marr was Honorary Colonel of the Waverley College Cadet Unit until his death on 16 November 1999, a period in excess of 40 years.