generally , a safety belt is essential during driving and often decreases the mortality rate of the passengers up to 50 - 75% . the majority of articles have been written about their benefits only , but it is also undeniable that in the case of improper use , seat belts can even be dangerous and life - threatening ( 1 - 4 ) . the following report presents a rare mortality case with fatal asphyxia caused by the seat belt , referred to forensic department . here the examination of the body and the results of the autopsy , toxicology and pathology tests are described from the viewpoint of forensic medicine . the deceased was described as a 49 year old man who was driving with a high speed of 110 kilometers per hour , in a highway in tehran . he died instantly without collision with the dashboard , steering wheel or any other part of the car according to the statement of the car passenger . the body belonged to a 49-year - old male , weighting approximately 85 kilograms , height 175 centimeters , with formal clothing and was examined in tehran forensic autopsy center . rigor mortis had been established and bruises with natural color were developed on the posterior surfaces of the body . time of death was estimated to be within the last 24 hours . in the examination , the deceased was in relatively good health and adornment . on the head and face , there were no signs of assaults , pressure around the mouth and nose , congestion , conjunctival hyperemia and petechiae in the eye , foreign body in the mouth , or bone fracture . on the neck , strip - like bruises were visible on the left side . on the trunk , strip printed abrasion was seen starting from the upper left shoulder and extending diagonally to the right side ( possibly the pressure of the seat belt ) . cardiopulmonary resuscitation signs were n't seen on the chest . on the extremities , abrasions were visible on the dorsum of the left wrist and anterior of the right forearm , abrasions and bruises were present on anterior right forearm and right groin . defensive injuries , electrical signs , fracture and dislocation of joints were nt visible and tangible . no signs of intracranial hemorrhage ( ich ) , intraventricular hemorrhage ( ivh ) , sub - arachnoid hemorrhage ( sah ) , brain contusion , and space - occupying mass lesion were seen . hematomas were evident under the skin and between the muscles in accordance with the strip - like abrasions and massive bruises in the left intercostal muscle , in addition to hematomas on left side of neck and left anterior shoulder . the hyoid bone and thyroid cartilage in the neck were normal . in cutting the throat and larynx and trachea , hematomas were visible around the muscles of the left side of throat and larynx . there was no sign of fracture and dislocation in larynx or foreign body in the airway . the body was also assessed in prone position and in autopsy of posterior spinal and dorsal cervical spine , no pathologic finding was found . no abnormal peripheral blood or fluids were detected in the two sides of thoracic cavity . lungs were congested in appearance and had a spongy consistency when touched and had no edema at the cutting . atherosclerotic stenoses were absent with a normal consistency and in slicing the heart muscle , fibrosis and hyperemia were nt evident . the abdominal cavity was open with no blood or other abnormal fluids . in the intra - abdominal organs , liver and spleen were normal and were not teared . other intra - abdominal organs were deployed without disruption to their anatomical location . to determine the cause of death in addition , vitreous , urine , bile , gut , and stomach samples were evaluated from toxicologic viewpoint . finally , based on the results of examination , autopsy , and toxicology , the compression of neck critical elements such as carotid sinus was determined as the cause of death . in addition to the speed , the road type , and the mechanism of the accident , type of the belt is also important in causing injuries ( 1 , 2 ) . there are different types of safety belts in vehicles including femoral belts , diagonal belts ( shoulder ) and three - point seat belts ( thigh and shoulder ) ( 3 , 5 , 6 ) . these belts are now used in the rear seats , and all new cars have three - point seat belts . if the femoral belt is fastened too high and placed on top of the hips , it can cause fracture on the body of vertebrate and transverse processes . improper use of this type of seat belt can also lead to soft tissue injuries and even small bowel perforation and rupture of solid organs ( 8 , 9 ) . while all of these injuries are caused by higher fastening of the safety belts , even with the proper use of seat belts crossing over neck can happen . in this case , hip goes lower at the time of the collision of seat and slides under seat belt . however , most abdominal cavities and spinal cord injuries are due to high fastening of seat belt ( 10 - 12 ) . any damage to the small intestine and colon and lumbar spine at the level of safety belt is called safety belt syndrome , abrasion and laceration of the abdominal wall is also common and is seen in 30% of patients and has been first reported by braunstein , garrett . by using three - point belts , collision with the dashboard and steering wheel will be avoided . however , this belt type may lead to fracture of ribs , sternum and clavicle and neck vertebrae ; strangulation and hanging on the left side of the car have also been reported ( 13 - 15 ) . a diagonal abrasion across the chest is usually associated with a three - point belt accompanied with fracture of ribs , sternum and clavicle in severe accidents and may also be associated with rupture of the aorta and ventricle of the heart and might cause vascular and tracheal and laryngeal lesions in the neck ( 16 ) . horizontal fractures caused by femoral belts in the second and third lumbar vertebrae was first reported in 1948 by chance and fracture of c7-t1 transverse process have been reported in using three - point seat belts . in the three - point seat belts , the most common lesions are mesenteric rupture and rupture of vessels in the mesentery of the small intestine , additionally a colon rupture at the anti - mesenteric region related to jejunum and ileum were reported . in an article by kirk patrick , 68 cases out of 82 patients had lesions in the small intestine and 19 had colonic injuries ( 11 , 13 - 15 ) . reported that from a total of 130 patients with lesions caused by the seat belt , only 34 patients had cervical lesions ( 24 had soft tissue lesions ) and 10 patients had neck fracture , all of which were associated with application of the three - point seat belts ( 16 , 17 ) . in the presented case , if the speed of the car was in the allowed range and safety belt was properly used , driver 's immediate death would not have happened . therefore , it is necessary to use the seat belt as a savior in the drivers , but we should not neglect the application of the standards of driving and the speed of the vehicle or else this very simple and valuable tool can change into a destructive one . it seems that , compression of neck critical elements such as carotid sinus by a three - point safety belt could be a rare potential cause of instant death following car accidents . all authors passed four criteria for authorship contribution based on recommendations of the international committee of medical journal editors .
although death is a gradual process , sometimes sudden death occurs in a fraction of a minute or seconds . here 
 we report a 49-year - old man without any underlying disease , which has instantly died in an accident scene due to compression of neck critical elements by a three - point seat belt . 
 the examination of the body and the results of the autopsy , toxicology and pathology tests are described from the viewpoint of forensic medicine .