Arthur Halloran, Commissioner for Crown Lands in the Wide Bay–Burnett, reported in 1854 that a white man known as Gilburri, “who for the last fifteen years has been living among the Aborigines, and who is said to have instigated them to commit depredations,” had been captured by Sub-Lieutenant Bligh.
Fahy was delivered to Brisbane. A widely cited account places him, five days after capture, in the same cell as Dundalli — hanged on 5 January 1855 for the murder of sawyer William Boller. The two men regarded each other as tribal brothers. Wikipedia’s Dundalli entry also corroborates a separate meeting in June 1842, before Fahy reached the Bunya Mountains.
The court sent him to Cockatoo Island, not the gallows. Gregory needed an experienced bushman. The deal was a pardon for a guide. Fahy accepted.