On 10 October 1865, Sykes went poaching with a group of six other men. Evidence suggests that Sykes had often poached in the past, but he had never been caught before. On this night the men were challenged by a group of gamekeepers, and in making their escape Sykes and a number of other men assaulted one of the gamekeepers. The gamekeeper died from his injuries, and a reward was offered for information about the attack. Eventually, the government offered a free pardon to anyone willing to give evidence, whereupon one of the seven men, Robert Woodhouse, gave evidence against the other six. Four of the men, including Sykes, were found guilty of manslaughter, and received life sentences with a minimum of twenty years of penal servitude.