As far as I am aware, there is no known means of medically assessing the intensity or otherwise of the pain a person is going through. When related to injury, medical evidence can only describe the nature of the injury but not the pain that goes with it. The more severe the injury the more likely the severity of the pain. Such pain can merely be imagined by a person who has seen when and how the injury occurred or who sees the nature of the injury later and was told how it happened including the medical doctor who may have treated the victim and noticed the agony he expressed by words or action or through groaning; or to whom the nature of the injury is described and the circumstances in which it occurred. For instance, a person who saw how any person’s limb, e.g. leg, was crushed by a heavy object would literally feel, pathologically, some reflexes which tend to register in him that the victim has undergone severe pain. When told about it he will likely imagine the severity of the pain. But the real nature of the pain can best be experienced or described by the victim.
– Uwaifo JSC. C & C Constr. v. Okhai (2003) – SC.8/1999
