At the Supreme Court in Sydney on Saturday 7th November 1840 several men were tried for bushranging. Two of them would be dead with the month.

James Martin, James Mason, assigned servants to Mr. Blaxland; and James Walker, James Howard and Robert Rawson, assigned to Mr. Bettington, were arraigned at the bar; James Martin for the wilful murder of John Johnson by shooting him in the head with a pistol, on 24th March 1840 at Gammon Plains (Merriwa). Mason and Walker were charged with being present at the time, and aiding and assisting; and Howard and Rawson for being accessaries after the fact. All the men pleaded not guilty and a lengthy trial followed. Two of the witnesses called, John Green and Thomas Kievers were approvers. John Green had been engaged in the outrage that had occurred at the house of Henry Pelham Dutton when John Johnson was shot.

Henry Dutton who was a settler at Gammon Plains, was the first witness called. His residence was situated about a mile and a half from Mr. Bettington's place and about three miles from Mr. Blaxland's. Dutton testified that the bushrangers came to his house about half an hour after sundown; Mrs. Dutton and three children were in the bedroom at the time and Dutton was in the hall of the house when he heard a loud crash of glass in the front parlour. Upon opening the door he was confronted with two masked men who threatened him with a gun. He was held in the room and shortly joined by his family, three female servants and two of their children and two male servants. All four bushrangers were covered by masks which covered their whole head and reached to their shoulders with slits cut with a knife to see through; and were dressed in smock frocks and moleskin trousers. After about 45 minutes there was gunfire in the hall and John Johnson, carpenter to Dutton, was found to have been shot.

Thomas Kievers, an approver was called on as a witness. He was 22 years old and an Irishman from Co. Mayo who arrived on the Bengal Merchant in 1835. He was bred at Newcastle-upon-Tyne and was a travelling pedlar. He had been punished four times, twice for losing sheep, once for going away from his station without a pass, and once for refusing to carry rations fifteen miles; the first time he received fifty lashes, the second time a hundred, the third time twenty five, and the fourth time fifty lashes. He was at the same station near Boggy Bryne Creek, as John Walker and James Howard, two of the prisoners at the bar.  Kievers first took to the bush with James Mason on 9th March after being ill-treated by the superintendent who refused to give Kievers tea, sugar and tobacco. Kievers had been told by the superintendent after he had been punished the last time for refusing to carry the rations that he would be made to carry them every day all the winter a distance of fifteen miles.

Kievers testified that he and Mason together with Green and Dayley carried out two or three robberies together. (Green was an assigned servant to Mr. Blaxland and Dayley to James Bettington). The prisoners Martin, Mason and Walker went with Kievers to carry out the robbery on Dutton's house. They armed themselves with a large stick, a cut down musket and fowling piece. Later when some of the loot was found by the mounted police, articles included clothing, Wellington boots, a cruet stand, several gold rings, stockings, trinkets that had belonged to Mrs. Dutton and toy horses and men made of bone.

Approver John Green gave insight into the brutality and callousness of the gang in his evidence. He also testified that James Martin was a close associate of the notorious Opposum Jack and that he believed that Martin murdered Opposum Jack.

Henry Beaverson (Bevison) was another associate of this loosely knit gang who attempted to murder Kievers, and was himself later murdered by James Martin.

A verdict of guilty against Martin, Mason and Walker was pronounced. The other two, Howard and Rawson, were found not guilty.

Martin and Mason were hanged on 8th December. John Walker was reprieved, perhaps because Henry Dutton recalled that Walker had prevented any violence occurring towards Mrs. Dutton.