In 1838 O'Halloran retired from the army by the sale of his commission, and sailed for South Australia the same year with his wife Jane O'Halloran, their sons
Thomas Joseph Shuldham O'Halloran and George Waring Wright O'Halloran and his daughter Annie Helen Lucy O'Halloran (by his first wife), in the
Rajasthan, landing at
Glenelg in November 1838. Upon his retirement he was appointed as a member of the
South Australian Legislative Council, retaining the position until February 1851. In March 1857 he was elected as a member of the Legislative Council and served until his resignation in June 1863.
Maria controversy . In June 1840, the brig
Maria set sail from
Port Adelaide towards
Hobart. By July 1840, stories and rumours had circulated that all 26 people on board had survived a shipwreck, but had been killed by members of the Milmenrura, a clan of the
Tanganekald people, along the
Coorong. After a police investigation, which discovered several mutilated bodies and determined who the murderers were believed to be,
Governor Gawler ordered O'Halloran (as police commissioner) and Police Inspector
Alexander Tolmer to lead a party of police and sailors to the area. His orders were to find and execute those responsible. On 22 August 1840, after several days of interviews, investigations and a
drumhead court-martial, two Milmenrura men were publicly hanged on the Coorong in front of 65 people from their tribe. O'Halloran then told the people (through an interpreter) that their bodies were not to be taken down and that this was to be a warning against violence towards Europeans by
Aboriginal people. This was one of the most contentious incidents in South Australian legal history. At the time, Aboriginals in South Australia were considered
British subjects, and therefore
deemed to be under the protection of British law. Gawler's ordering of a drumhead court-martial and the executions was not well received by the London authorities and contributed to his removal as governor. At that same time O'Halloran's younger brother, Captain (later Major General) Henry Dunn O'Halloran (1800–71),
69th Regt., posted at
New Brunswick, Canada, was conducting a significant study of the language and customs of the indigenous
Mi'kmaq people. ==Character==