Justice, at bottom, can only be revenge. Murder and mayhem cannot be undone or somehow ameliorated. The loss of a life, a limb, or an organ is permanent. Other injuries take time to heal, and may heal imperfectly; the healing time and its attendant costs are lost, in any event. Theft is rarely made whole.
Aside from the inculcation of morality, our surest protection from predation is the promise of swift and sure vengeance. When the state fails in its duty to exact that vengeance, it becomes illegitimate.