He was stationed at various locations in central and northern Queensland between 1867 and 1880 conducting regular punitive expeditions against clans of Indigenous Australians who resisted colonisation.

In his years of duty for the Native Police, Johnstone led many punitive expeditions and "dispersals" consistent with government policy, resulting in thousands of Aboriginal people being killed or displaced from their traditional lands.

Lieutenant-General Need married an Indian woman, most likely the daughter of Saadat Ali Khan II, and had several children with her, one of whom was Robert Johnstone's father.

[3] It is notable that a number of other Native Police officers, such as Lieutenant John Murray have similar family backgrounds involving Indian grandmothers.

During this time Robert claimed that he came in frequent contact with the remnants of the local Aboriginal population (probably the Koroit gundidj clan of the Gunditjmara) and with those residing on the Wannon River.

This government funded paramilitary force had been in existence in various forms throughout Colonial Australia since 1837 and consisted of white officers in command of mounted and armed Aboriginal troopers.

These camps "were dealt with in the usual and only effectual mode for restraining their savage propensities", which meant indiscriminate shooting of the occupants by Johnstone and his troopers to clear them from the area.

[9] The brutal operations of the Native Police were well known throughout the colony and beyond, where troopers would usually "make a night attack on the slumbering tribe and generally slay a large number".

[11] Later in the same year, after some Yuibera men had speared five head of cattle at Koumala, Johnstone chased members of the clan to some islands offshore and when they tried to return to the mainland "such a lesson was administered" to keep them from "committing outrages in that locality".

[12] In 1868 a large group of Aboriginals killed 7 cattle at Greenmount with Johnstone and his troopers "administering a lesson to the blackskins...who richly merit a severe one".

[14] Johnstone himself describes in his memoirs other punitive expeditions he led while stationed at Nebo, including that of "punishing blacks" for the killing of a shepherd at May Downs.

When taking cover from this unexpected attack, Johnstone found a large Aboriginal weapon-making site in a ravine between Tierawoomba and Blue Mountain.

Although having armed settlers partake in the punitive expeditions of the Native Police was against official orders, Johnstone allowed West Fraser to participate on the "promise of secrecy and obedience".

[16] In March of the same year, Johnstone was again out with his troops endeavouring to punish "the blacks" after the killing of a Chinese shepherd at Mt Heilcalong station near Lake Elphinstone.

[18] While in the Mackay region, Johnstone had evidently become acquainted with John Ewen Davidson, a sugar planter who had formed plantations in several parts of Queensland[original research?].

Johnstone describes one incident early in his stay where "the blacks" used their wooden shields as a movable barricade and the cover of smoke from deliberately lit fires in a counter-attack on the property's homestead.

[21] Johnstone and his troopers, together with armed sailors and volunteers, scoured the coast from Cardwell north to Cooper Point, searching every Aboriginal camp they came across.

[25] A travelling correspondent to the Valley of Lagoons area by the name of Richard Bird Hall wrote several letters to the Queensland Government and to various newspapers about the murderous actions of Johnstone and his troopers.

Johnstone and his troopers sailed to the area in their police boat and found the "Goodwill" abandoned and burnt on a beach in Trinity Bay where the modern-day community of Yarrabah is now located.

"The blacks were given a proper warm reception" when Johnstone arrived and after proceeding inland for 3 miles his troopers dispersed another group of local Yidinji people first by firing on them from a distance and then charging amongst them.

They then sailed further south to the Gladys Inlet (which is now known as the Johnstone River) where a large group of Aboriginals led by a very tall man decorated with pipeclay resisted the troopers' approach.

Johnstone sailed a little further up the river towards its bifurcation, noting the dense jungles and thick soil which could be exploited for sugarcane farming despite the area being populated with Aboriginal people.

[30] After several days evaluating the potential of clearing this region of thick jungle for exploitation of cash crops such as sugar, the group sailed back to the mouth of the river.

Needing water, Dalrymple directed Mr. Thompson towards the smoke from an Aboriginal beach camp on the mainland at a place now known as Palm Cove and Johnstone and his troopers proceeded there in the police boat.

At Constantine Point at the mouth of the Mulgrave River, Johnstone found a large gunyah and stole the mummified remains of an Aboriginal woman from it.

Dalrymple's description was "The head of this mummy is small – the animal organs being developed to distortion, the mental being next to nil; in fact, it is of the very lowest type of human formation."

[30] The crew of a sugar trading cutter by the name of Albert and Edward which anchored in Challenger Bay off Palm Island, kidnapped some local Aboriginal women for sexual purposes.

[15] After "the blacks" had robbed a hut at Dalrymple's Gap, sub-Inspectors Johnstone and Burrowes and their troopers tracked them to the coast at Seymour River estuary where they were "dispersed".

[35] In 1876, Johnstone with other Native Police officers in Alexander Douglas-Douglas and George Townsend, aided in the creation of a track from the Hodgkinson goldfields to the coast where Battle Camp became a port for the miners.

[15] Captain Thomas Harris of the schooner Douglas had three Aboriginals from the Dunk Island area to work loading guano and beche-de-mer from Chilcott Islet.