Some wee scumbag from County Durham, that's who.
The boys had entered the field and began chasing a flock of sheep, including lambs. As the cruel game escalated, the boys started striking the animals with sticks and corralling them closer to the edge of the quarry. In the culmination of the incident, Mr Thomas told the court how one of the boys managed to catch a trapped lamb, and kicked it off the edge of the cliff.
Mr Thomas then passed a photograph of the dead lamb to the 12-year-old boy, who started to cry.
That sort of thing can happen to the best of people, mind you. I was drinking cider down at the old malthouse with Gable Oak last winter, and he told me this sad story.