The Trial of Zairaf Ma'arad

Sa'afras Ali, Ahmed Awan and Sha'id Nizia were all sentenced to life in prison for the murder of Ross Parker. But Zairaf Ma'arad was found completely not guilty of anything,. Not guilty of murder, not even guilty of manslaughter or assault because he was obviously there. He admitted to being a part of this yet he got absolutely no prison tag for anything. I just can't understand it at all because he was one of the three men that admitted to having a part in the attack.