Innes was born in Sydney, New South Wales the eldest son of Major Joseph Long Innes (superintendent of police) and his wife Elizabeth Anne, the daughter of Thomas Reibey and Mary Reibey. Innes was educated at William Timothy Cape's school and at the King's School, Parramatta. He then went to England, and entered as a student at Lincoln's Inn in November 1856; and, after winning a certificate of honour in May 1859, he was called to the bar in November of the same year.
Having returned to Australia, Innes was admitted to the New South Wales bar in 1862, and practised till 1865, when he was appointed a district judge in Queensland. This position he resigned in 1869, and returned to practise his profession in Sydney. He also went into politics, and was returned to the New South Wales Legislative Assembly for Mudgee on 7 March 1872, in May of which year he became Solicitor-General in the first Parkes ministry, and in November of the next year Attorney-General in succession to Edward Butler. Having been nominated to the New South Wales Legislative Council in 1873, he continued to hold office as Attorney-General in the Parkes Ministry until the break-up of the Government in February 1875. In the previous year he had accompanied Sir Hercules Robinson, the then Governor of New South Wales, on his special mission to Fiji, in connection with the annexation of the island to the British Crown, and was knighted in January 1875 in recognition of his legal services on that occasion. Sir George acted as Chairman of Committees in the Legislative Council till August 1880, when he succeeded Francis Bathurst Suttor as Minister of Justice in the third Parkes ministry, this post he resigned in October 1881, on being appointed a Puisne Judge of the Supreme Court of New South Wales. Sir George married, in 1865, Emily Janet, daughter of Hon. John Smith, M.L.C., of Llanarth, Bathurst, New South Wales.
Innes died on 28 October 1896 in England, survived by his wife, five sons and a daughter.
- Allars, K. G. "Innes, Sir Joseph George (1834–1896)". Australian Dictionary of Biography. Canberra: Australian National University. Retrieved 2 January 2014.
- Mennell, Philip (1892). " Innes, Hon. Sir Joseph George Long". The Dictionary of Australasian Biography. London: Hutchinson & Co. Wikisource
- "Sir Joseph George Long INNES (1834 - 1896)". Parliament of New South Wales.