Imam al-Sha'bi (may Allah have mercy on him) narrates that Sayyiduna Ali (may Allah be pleased with him) ruled two-thirds of the blood money concerning the one who pinched, the one who bucked, and the one who died of a broken neck. Ibn Abi Za'idah explains it in detail: three girls were playing together. One of them climbed onto another, and the third pinched the one being ridden upon; she bucked, so the one on top fell and her neck broke. So Sayyiduna Ali (may Allah be pleased with him) ruled two-thirds of the blood money in this matter, and because the girl who died had herself contributed to it, he waived her one-third (thulth) share.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الديات / 16401