O'Callaghan was born on 11 April 1845 near Windsor along the Hawkesbury River in New South Wales. He was the eldest son of servant and grazier Jeremiah Callaghan and his wife Margaret, he attended Todd's Academy in Sydney and spent much of his childhood in Britain and North America. Back in Australia, the family established a form on the Mortnington Peninsula, before relocating to Melbourne in 1860. O'Callaghan joined the Victoria Police Force on 16 November 1887, starting off as a Detective, Third Class. Prior to joining the police, he spent some time mining for gold, in what was ultimately a luckless endeavour.
Career
Although O'Callaghan quickly established himself as a successful crime-buster, he was also notorious for self-destructive behaviour. For instance, in 1871, he was demoted for giving alcohol to a prisoner, and in 1882 he was suspended from duty for "disrespectful demeanour towards the Royal Commission on Police". Nevertheless, he was promoted to Officer in 1886; Inspector in 1892; Superintendent in 1895; and Chief Commissioner on 1 July 1902. O'Callaghan authored the Victorian Police Code in 1906. He retired from the police force on 31 March 1913. O'Callaghan was also an active member of the Australian Natives' Association. Having joined in 1876, he was elected as foundation chief president in 1877, serving in the position till 1878. He also edited the inaugural issue of the foundation's journal, the National Journal. O'Callaghan was the President of the Royal Historical Society of Victoria from 1925 to 1927.
Later years and personal life
O'Callaghan was a Catholic and a member of the Melbourne Cricket Club. On 20 June 1882, he married schoolteacher Mary McDonald at St Francis' Church in Melbourne. They had seven sons and five daughters, including three sets of twins. McDonald died in 1914 and two of their children also predeceased him. Having been in poor health for several months, O'Callaghan died on 1 September 1931 at his North Carlton residence, aged 86. He was buried at the Melbourne General Cemetery. In his novel Power Without Glory, published in 1950, Frank Hardy modelled the "corrupt chief commissioner" Thomas Callinan after O'Callaghan.
