There’s an odd little tale in a pardon for homicide from 1236 – see CPR Henry III vol. 3 p. 167. Walter, son of Walter Stiek was in deep trouble – he was said to have killed his brother, Hugh, and, unless he could attract royal sympathy, he would be liable to capital punishment. So he came up with a rather unlikely sounding explanation, which would mean that he might be pardoned as unlucky rather than executed as homicidal. He said that it had all been a terrible accident – he had been engaged in a spot of ploughing, and had thrown the ‘swingle tree’ of the plough (what do you mean you don’t know what a swingle tree is) at an ox (such use of the ‘swingle tree’ is, I am assuming, not recommended ploughing practice) and – pyoiiiing – it rebounded from the ox’s horn, hit poor Hugh, and did for him. The physics of this seem a bit unlikely to me, but then I can claim no particular expertise in the way of swingle trees.