The retrospective analysis of the autopsy records of 50 homicides showed that the Injury Severity Score (ISS), a numerical scoring system initially developed to quantify the severity of injuries sustained in road traffic accidents, can also be useful for objectively describing and ranking the overall severity of trauma with regard to forensic issues. The present case report illustrates to what extent the ISS can help to assess the contribution of each assailant in homicides committed by several perpetrators. In the case presented the court was convinced that one perpetrator had inflicted four deep stab wounds to the victim's face (each with bony lesions), 2 stabs to the chest piercing the right lower pulmonary lobe and causing a haemothorax of 200 ml, an abdominal stab wound without involvement of a parenchymatous organ as well as multiple defence wounds of the arms. Thereafter, a second perpetrator was thought to have inflicted several heavy blows with a full water bottle causing severe contusions on the right side of the forehead, the chin, the left side of the face and a spider's web fracture of the frontal bone. Using the ISS an injury severity score of 24 was assigned to the first complex of injuries and a score of 10 to the second complex. The forensic conclusions with regard to prognosis and lethal outcome are discussed.