John Robert Kerr was born in Sydney on 24 September 1914, a son of Harry Kerr and his wife Laura (nee Cardwell). He was educated at Fort Street Boys' High School. In 1936 he graduated LLB with first-class honours and the University Medal. He was admitted to the Bar on 17 February 1938. In that year he married Alison Worstead, who died in 1974. There were three children. In 1975 he married Mrs Anne Robson. During the second World War he served with the 2nd AIF and attained the rank of Colonel on the staff of General Sir Thomas Blamey in the Directorate of Research and Civil Affairs.

He took silk in 1953. A member of the New South Wales Bar Council from 1960 he became Vice-President 1962-3 and then President in 1964 of the Bar Association. From 1964 to 1966 he was President of the Law Council of Australia and presided at the Third Commonwealth and Empire Law Conference in 1965. His work was recognised by his appointment as CMG and by his receiving honorary life membership of the American Bar Association and of the Law Society of England and Wales. He had much to do with the establishment of the Law Association for Asia and the Pacific, was chairman of its inaugural committee, and its first President (1966-70).

In 1966 John Robert Kerr became a Judge of the Commonwealth Industrial Court, and was also a Deputy President of the Trade Practices and Copyright Tribunals, and a Judge of the Supreme Court of the Australian Capital Territory and of the Courts of Marine Inquiry. He became Chief Justice of NSW on the retirement of Sir Leslie Herron.

Mr Justice Kerr was appointed KCMG in 1974, and was also made K St J. He resigned as Chief Justice on 27 June 1974 in order to become Governor-General of the Commonwealth. Following the events of 1975 public opinion turned against Kerr and he resigned in 1977. He retired to London and died on 25 March 1991.

During his time as Chief Justice of NSW, John Kerr implemented major reforms under the Supreme Court Act 1970 (NSW) and established an Executive Office to bridge the administrative and judicial responsibilities of the Court. He oversaw the construction of new accommodation for the Federal and State law courts building in Queens Square. A distinguished lawyer, diplomat, with a brilliant academic mind, Kerr was an enthusiastic supporter of legal aid, legal reform and legal education. Sir John Kerr resigned from the office of Chief Justice of NSW in 1974 to accept the position of Governor-General of Australia.