Autopsy & forensics

Frontal impact

• Most common type of impact associated with crash fatalities (NHTSA: Fatalities in Frontal Crashes Despite Seat Belts and Air Bags [Accessed 7 April 2025])
  • While rear impacts are more common, frontal impacts generally result in more severe injuries and death
  • Occupants involved in frontal impacts had a significantly higher injury risk compared to those in rear impacts (Traffic Inj Prev 2022;23:176)
• Occurs when 2 vehicles collide head on or when a single vehicle hits a stationary object head on
• Deceleration leads to the moving forward of the occupants, impacting the windshield and dashboard
• Wearing a seatbelt and using an airbag system may reduce the severity of trauma (Annu Proc Assoc Adv Automot Med 2000;44:149)
• Injuries to the driver
  • Injuries to the knees: abrasions, lacerations or patellar fracture at the side of impact with the dashboard and indirect injuries due to the compression process to the thigh present as an acetabular fracture or posterior hip dislocation (Afr Health Sci 2018;18:321)
  • Presence of intra-articular foreign bodies (fragments from the broken dashboard) is possible (Ann R Coll Surg Engl 2015;97:e21)
  • Energy can be transmitted through the femur upward or through the tibia downward
  • Impact of the knees against the dashboard commonly causes fractures of the tibia, fibula, femur and pelvis
  • Forceful application of the brakes results in foot and ankle fractures (Afr Health Sci 2018;18:321)
  • Grasping the steering wheel may cause scaphoid fractures (Int J Surg Case Rep 2020;66:412)
  • Patterned abrasions and contusions from the contact with the steering wheel
  • Severe chest injuries due to impact with the steering wheel (bilateral rib fracture, sternum fracture, contusion and lacerations of the internal organs) (Ann Emerg Med 2005;45:43)
  • Partial or complete transection of the aorta may occur (at the junction of the aortic arch with the descending aorta) (Cureus 2021;13:e12726)
  • Glass splinter injuries when the head hits the windshield (V shaped lacerations)
  • Dicing injuries or sparrow foot lacerations to the left side of the face and left arm of the driver from impact with the side window; the front seat passenger will have similar injuries but on the right side
  • Fragments of tempered glass embedded in the wound may be seen
  • Ejection of the driver or the front seat passenger through the windshield may cause accidental cut throat injuries (Med Sci Law 2018;58:183)
• Injuries to the front seat passenger
  • Injuries to the front seat passenger are similar to those sustained by the driver (without steering wheel impact) (Forensic Sci Int 2021;324:110853)
  • Front seat passenger may be ejected out of the vehicle through the windscreen, which increases the risk of secondary injuries or running over
  • Injuries from seatbelt prove that one was worn and could help in the identification of passengers' position
• Injuries to the rear passengers
  • Unrestrained rear passengers may be thrown into the front compartment of the vehicle
  • Additional injuries from impact of internal fittings (door handles) (Forensic Sci Med Pathol 2021;17:235)
  • Whiplash injury due to the sudden deceleration is possible
  • Passengers can be thrown out of the car

Side impact

• When a vehicle impacts the side of another vehicle or skids sideways into a flexed object (Int J Trauma Nurs 1995;1:64)
• All injuries seen in frontal impact collisions can occur
• Severe injuries since there are no other components to absorb the force of impact
• More severe to the passenger on the side of the impact
• Side impact causes an abrupt lateral inclination of the head, compressing the cervical spine close to the impact, with the tensile stress to the cervical spine on the opposite side of the impact (J Craniovertebr Junction Spine 2014;5:33)
• Side impact airbag (SAB) deployment is generally associated with a reduced risk of severe injuries in side impact crashes (J Trauma Acute Care Surg 2012;73:914)
  • Occupants with deployed SABs had a lower risk of sustaining serious injuries compared to those without such protection
  • SABs are also associated with an increased incidence of upper extremity injuries linked to the forces generated during airbag deployment (J Trauma 2008;64:1297)

Rear impact

• Generally low velocity impacts (Accid Anal Prev 2015;79:1)
• May cause acceleration injuries (e.g., whiplash associated disorders)
• Whiplash injuries are more common where seats do not have a head restraint
  • Sudden force resulting from the impact propels the body forward while the head lags momentarily due to inertia, resulting in a rapid extension and flexion of the neck
  • This abrupt movement strains the cervical spine, muscles, ligaments and soft tissues, resulting in regional injuries

Rollover or roof impact

• Different injury patterns can occur
• May cause death from asphyxia (compression, positional or a combination of both) if the individual is trapped inside the crashed vehicle or is ejected and becomes trapped beneath the vehicle (Am J Forensic Med Pathol 2008;29:14)
• Ejection from the vehicle is possible in nonbelted occupants (Traffic Inj Prev 2018;19:734)

Injuries due to seatbelt or airbag

• Seatbelt mark: patterned bruising / abrasion on the chest or abdominal wall corresponding to the position of the straps of the seatbelt (Forensic Sci Med Pathol 2021;17:235)
  • Different types of seatbelts: lap strap, shoulder diagonal type, diagonal plus lap strap and shoulder harness
  • Seatbelt pattern might help in differentiating occupant locations within the motor vehicle
  • Absence of seatbelt mark is not a sure sign that the driver / passenger was unrestrained (Forensic Sci Med Pathol 2007;3:258)
• Injuries from airbags vary from minor contusions to more severe injuries such as abdominal wall injuries, rupture of the mesentery, intestines, bladder, compression of the aorta, lumbar spine fracture
  • Chance fractures: an unstable, flexion distraction injury of the spine, typically at the thoracolumbar junction (Clin Case Rep 2023;11:e7886)
  • Airbag deployment may cause cranial, facial or cervical injuries (Ulus Travma Acil Cerrahi Derg 2010;16:379)
  • Airbag deployment may cause burn injuries (J Med Case Rep 2008;2:91)
  • Burns may vary from superficial to second degree, with arms and thorax being the most affected areas (J Forensic Odontostomatol 2007;25:57)

Vehicle height differences

• Mismatch in vehicle height during a crash can lead to misaligned impacts, with taller vehicles often causing more severe injuries to occupants of shorter vehicles due to greater force application at different levels of the body
• Crashes between vehicles of significantly different heights can result in occupant compartment intrusion
• Occupants of shorter vehicles are more likely to sustain severe leg injuries due to impact forces being concentrated on the lower part of the body (Accid Anal Prev 2004;36:761)

Impact with the frontal part of the vehicle

• 3 typical accident phases: primary impact, loading (secondary impact) and tertiary / ground impact (Accid Anal Prev 2017;106:285)
• Mainly blunt force trauma; in some cases sharp force trauma
• Varying types of injuries, from superficial (abrasions, bruises, hematomas and lacerations) to degloving lacerations and fractures
• Primary impact injuries are patterned injuries caused when parts of a moving vehicle forcefully contact a pedestrian's body during impact
  • Point of impact in relation to the center of gravity
  • Patterned abrasions from the grill and headlight rim are possible
  • Height above the shoe sole might indicate the primary or approximate point of impact on the car (with nodding motion of the car potentially resulting in lower impact)
  • Flexion fractures close to the ankle with protrusion on the opposite side of the impact (Sud Med Ekspert 2023;66:33)
  • Bumper fracture may be seen from the contact with the bumper of the car, also known as tibial plateau fracture (Am J Forensic Med Pathol 2022;43:11)
  • Wedge shaped fractures (Messerer fracture) indicating the direction of the impact; the wedge tip points in the direction of the impact (Int J Legal Med 2016;130:1593)
  • Stretch type lacerations are frequent in the inguinal (groin) regions
  • When the vehicle is larger (truck or a bus) or in cases of children impacted by a car, the point of primary contact is going to be higher; primary injuries are going to be situated over the pelvis, abdomen, chest and head (Traffic Inj Prev 2005;6:185)
  • Primary impact to the lower leg might be associated with abrasions, contusions and formation of wound pocket (Sci Justice 2021;61:112)
  • Following the primary impact with a bigger vehicle, the body is thrown on the ground and the risk of run over injuries is increased
• Secondary impact injuries (loading phase) occur after the primary impact, when an initial blow below the pedestrian's center of gravity causes their feet to slide away, lifting the body onto the vehicle's path
  • During the loading phase, the feet of the pedestrian slide forward and the whole body is lifted off the ground and thrown onto the car hood
  • Both the pedestrian and the vehicle receive injuries / deformations (Sci Justice 2021;61:112)
  • Blunt trauma to the thorax is possible (rib fractures, pneumothorax or contusion of the thoracic organs)
  • Blunt abdominal trauma may occur (contusions and ruptures of the internal organs)
  • Head will impact the windshield or the upper or sidebar, which will have lacerations, facial and skull fractures as a result
  • Traces on the vehicle (blood, tissue particles, hair, etc.) might be linked to the victim
  • Specific crack patterns (spider web looking on the windshield of the vehicle)
  • In some cases (of high velocity of the vehicle), the pedestrian may fly over the roof
• Tertiary impact injuries result from the body striking the ground following the secondary impact, with head injuries being common and potentially fatal
  • Injuries sustained during the ground impact might be superimposed on the primary impact injuries
  • Extensive abrasions known as graze abrasions, friction burns or road rash injuries, avulsions and bone abrasions are typical for this phase (J Burn Care Res 2025;46:1)
  • Internal organ damage (contusions, lacerations) and fractures of the skull, ribs, spine and fractures of the limbs

Impact with the side part of the vehicle

• Rotational movement of the pedestrian
• Different types of injuries are possible as well as injuries from prominent parts of the vehicle

Impact with the back side of the vehicle

• Low velocity impacts
• Pedestrians may be thrown away and run over

Run over

• Tire tread marks can be seen over the skin or the adjacent clothes (Forensic Sci Int 2001;119:217)
• Clothing of the victim will be soiled with grease, oil and dirt from the undersurface of the vehicle (Eur J Law Publ Adm 2018;5:137)
• Head may be crushed, causing gross distortion (Accid Anal Prev 2019;129:362)
• Severe injuries may occur to the chest, pelvis or abdomen (Ann Emerg Med 1989;18:881)
• Severe internal injuries, with comminuted fractures of the bones
• Ruptures and eversion of the internal organs
• Stretch marks are seen due to the overstretching of the skin
• Avulsion injury occurs when the wheel moves over a fleshy part, causing degloving of the skin and subcutaneous tissue (Rom J Leg Med 2013;21:165)
• Avulsion injuries are also known as flying injuries
• Burning and singeing of skin and hair as a result of the discharge of hot exhaust

Contributed by Biliana Mileva, M.D., Lorenzo Gitto, M.D., Mihaela Georgieva, M.D. and Metodi Goshev, M.D.

Which of the following injuries is most common in rear impact car to car collisions?

1. Cut throat injuries caused by ejection through the windshield
2. Patellar fractures due to the knees impacting the dashboard
3. Scaphoid fractures from grasping the steering wheel
4. Severe rib fractures and sternum fractures from hitting the steering wheel
5. Whiplash injuries

E. Whiplash injuries are more commonly associated with rear impact collisions than with frontal impacts. In a rear impact scenario, the sudden force propels the body forward while the head lags momentarily due to inertia, resulting in a rapid extension and flexion of the neck. This abrupt movement strains the cervical spine, muscles, ligaments and soft tissues, resulting in regional injuries.

Answer C is incorrect because this is a common injury in frontal impacts due to the driver gripping the steering wheel tightly during the collision. Answer D is incorrect because frontal impact collisions often cause severe chest injuries due to the driver's chest hitting the steering wheel. Answer A is incorrect because although less common, ejection through the windshield can occur in high impact frontal collisions, leading to cut throat injuries. Frontal impacts are less likely to cause whiplash compared to rear end collisions. Answer B is incorrect because patellar fractures and other knee injuries are common in frontal impacts when the knees strike the dashboard.

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Reference: Traffic related deaths

In a car to pedestrian collision, which of the following injuries is most likely to occur during the secondary impact phase?

1. Abrasions, bruises and hematomas to the legs
2. Bumper fracture or tibial plateau fracture
3. Extensive abrasions, avulsions and fractures of the skull and spine from ground impact
4. Rib fractures and pneumothorax from blunt trauma to the thorax
5. Wedge shaped fractures indicating the direction of the impact

D. Rib fractures and pneumothorax from blunt trauma to the thorax. During the loading phase, the feet of the pedestrian slide forward and the whole body is lifted off the ground and thrown onto the hood of the car, resulting in blunt trauma to the torso and to the head. The secondary impact phase, which involves the pedestrian being thrown onto the hood, can result in blunt trauma to the thorax leading to rib fractures and pneumothorax.

Answer B is incorrect because bumper and tibial plateau fractures are typically associated with the primary impact phase when the pedestrian's lower leg strikes the vehicle's bumper. Answer E is incorrect because wedge shaped fractures are associated with the primary impact phase and indicate the direction of the collision. Answer A is incorrect because abrasions, bruises and hematomas to the legs are typical of the primary impact phase, when the pedestrian initially contacts the vehicle. Answer C is incorrect because these injuries are most commonly sustained during the tertiary impact or ground impact phase, when the pedestrian hits the ground.

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Reference: Traffic related deaths