Motor vehicle accidents can cause a variety of injuries to occupants, pedestrians, and cyclists depending on the type and severity of impact. Common causes of injury include impact with interior vehicle surfaces, intrusion of objects into the passenger compartment, and ejection from the vehicle. Injuries may involve any body region. Autopsies of crash victims aim to determine cause of death and document findings for legal purposes. Investigations also examine crash scenes and vehicles to understand accident dynamics.

1. Deaths caused by Motor vehicle
accidents (MVA)
•Occupants of vehicle ( driver, front seat passengers
and back seat passengers)
•Injuries of pedestrian
•Pedal Cyclists ( Bicycle mishaps)
•Two wheeled Motor cycles (motor cycle mishaps)
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2. Injuries in MVA are the result of
1. Impaction of individual on some portion of exterior
or interior of the car
2. Violation of integrity of passenger compartment by
intrusion of part of the car or of another object .e.g.
another vehicle or lamppost , into the passenger
compartment
3. Ejection from the MV , either in part or entire
4. Fire
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3. Mechanism of injury :- Occupants of
the vehicles
Mechanisms of Injury
a. Force of the impact
b. The direction of the impact
c. Where the casualty was seated
d. Use of seat belts or other forms of restraint
e. The intrusion of external objects like poles or
timber
f. Whether there is ejection from the vehicle
g. Behavior of vehicle after impact, e.g. overturning
or catching fire.
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4. Categories of Motor Vehicle accidents-
depends upon direction of impact of vehicle
•There are four categories
1. Front impact crashes
2. Side impact crashes
3. Rollovers
4. Rear impact crashes
However, during a collision or accident combination of four
basic types may also occur ( on front impact – car is deflected,
roll over and slams sideways into a tree)

5. Front collision/impact crashes
•Occur when two vehicles collide head –on or the front
part of vehicle strikes a fixed object , such as telephone
pole or wall or tree
•As a result of kinetic motion , occupants will move
forward ( if unrestrained) and impact the steering
wheel or dash board , windshield or A beam of vehicle
(Deceleration injury )
•Patterns of injury will depend on the position of
occupants within the vehicle
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7. Driver Injuries ( summary)
•Head may impact windscreen , visor area
•Chest may impact steering wheel , resulting
in injuries to chest and abdominal organs
•Upper extremities
•Lower extremities
•Dicing injuries from fragments of side windows
and rear windows glass ( right side of face and
right arm)
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8. Injuries to head , neck
•Surface injuries due to shattered
windscreen (dicing injuries)
•Facial fractures
•Skull fractures : basilar skull fractures
•Brain injuries
•Neck fractures from hyper-flexion and hyperextension
injuries(Fracture dislocation of upper cervical -
vertebrae is common
•Posterior atlanto-occipital fracture /dislocation due to
hyper-flexion
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9. Injuries to chest
a. Surface injuries including seat belt marks
b. Transverse fracture of sternum
c. Rib fractures
d. Lung contusions and lacerations
e. Heart: contusions and or lacerations
f. Rupture / transection of aorta
g. Mediastinal haematoma
h. Diaphragm may rupture
( steering wheel impact type of injury)
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10. Extremity injuries
•Wrist or forearm fractures , closed or open , consistent
with hands on wheel attitude at impact
•Fracture of patella(e) or femur as the knees impact the
dashboard
•Ankle fractures may occur if foot /feet are braced
against floorboard, or pressed firmly against the
accelerator or brake pedal ( look for impressions) or if
the floor buckles at impact
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11. • Front seat passenger
• Injuries similar to driver but unrestrained passenger will strike dash board and
not the steering column , so no steering wheel imprint on chest under ordinary
circumstances
• Dicing injuries on left side of face and or arm
• Rear seat passengers
• Unrestrained may be thrown forward , impacting the back of front seat , the
front seat passengers , the sun visor area or even the windshield

12. Restraining devices
• Seat belt injuries
• Foetal injury and death
• Bruising of chest wall and abdominal wall
• Intestinal , omental and mesenteric lacerations and intestinal
contusions can occur
• Rupture of spleen , liver, pancreas, caecum and bladder and
crushing of aorta (Seat belt syndrome )
• Injuries from air bags
• Abrasions to face, neck and chest
• Minor friction burns to upper limbs, eye
injuries
• Asphyxia

13. Side impact crashes/collisions
•Usually occur at intersections when one vehicle
impacts another or may also occur when a car skids
sideways into a fixed object , impacting on its side
•If impact on right side, driver tends to have right sided
injuries and front seat passenger will have fewer
injuries due to cushioning by the driver
•If impact on left side of vehicle, passenger will tend to
have left sided injuries , as will the driver if no
passenger is present

14. Roll over collisions
•Generally less lethal than head on and side impact
collisions provided individual is not ejected or vehicle
rolls into an unyielding object such as a tree.
• If no restraints are worn and occupant is ejected from
the vehicle or is thrown from passenger compartment
(occupant ejection).
•If partial , transient ejection occurs, body part involved
may be crushed or amputated.
•Overturning of car may result in pinning /crushing of
occupants (traumatic asphyxia)
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15. Rear impacts
•Impact is reduced or absorbed by some degree by
trunk and rear seat compartment
•Most common injury is “whiplash injury of the neck”
•Whiplash injury
“ due to violent acceleration or deceleration force
applied to passenger , usually front seat occupant”
• Fracture dislocation of upper cervical vertebrae or less
commonly in lower part of the spine at about C5-6.

16. Trace evidence
•May be found inside the vehicle or on the victim’s
body
•Inside the vehicle: hair, blood, clothing fibres or
strands from occupant left on broken glass, knobs or
impact surfaces
•On the victim’s body: paint chips, glass fragments, or
broken pieces of the vehicle embedded in wounds
• Toxicology analyses for drivers and passengers should
include tests for alcohol, CO, prescription and non
prescription drugs ,marijuana ; other drugs of abuse such
as cocaine and opiates
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17. INJURIES OF PEDESTRIANS
•Primary impact injuries ( first part struck)
•Secondary impact injuries ( further
injuries caused by the vehicle)
•Secondary injuries , some times called tertiary
injuries ( injuries caused by victim striking objects
like ground )
OR
•Primary impact ( due to impact with vehicle)
•Secondary injuries ( due to impact with ground or
other object after being thrown off vehicle)
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18. Four factors influence type and
appearance of the injuries received
1. Speed of the vehicle at the time of
impact ( high speed, low speed and
hard braking impacts)
2. Type of vehicle involved
3. Whether or not braking occurred
4. Size and age of the victim (adult or
child)

19. Five categories of post impact trajectories
•Wrap : struck by bumper of car, which injures the
lower part of the leg- and by the front edge of the
bonnet , which injures upper part of leg and or
pelvis. (Primary impact).
•Following this, person is rotated so that upper half
body-head, shoulders and chest –is thrown against
bonnet, windscreen or windscreen surround
(Secondary impact)
•Victim falls off the front of car, finally coming to
rest after sliding across road surface ( tertiary
impact)
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20. • Flat projections: by flat fronted vehicles. Victim is thrown forwards
onto road surface in front and is exposed to being subsequently run
over.
• Wing top: person is struck by front corner of vehicle and is
carried over wing, falling to ground at side of or behind
vehicle.
• Roof top: occurs either at high speeds or when vehicle
accelerates after impact. Instead of being projected forwards
from bonnet after secondary impact , victim slides all the way
up windscreen and over the roof , coming to rest on roadway
behind.
• Somersault: feature of high speed impacts and occurs where
there has been sufficient force to the lower part of the body to
somersault the person into the air before he or she falls to
road surface.( NO SECONDARY IMPACT WITH
VEHICLE.)
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22. Patterns of injury: Specific injuries
•Surface injuries: on face, arms and legs broad grazed
abrasions; patterned imprint abrasions from tyre tread
marks; deep bruising of the calves from bumper bar
impact; lacerations (degloving , avulsion ) and under
cutting injuries
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23. Injuries to legs including Bumper fractures
•As bumper strikes lower extremities of pedestrian,
bumper fractures may be produced( open or closed
and involve one or both bones of lower leg).
•If both legs fractured at same level, implies that victim
was standing still at time of impact
•If legs are fractured at different levels , this implies
that victim was walking or running when struck
•A side impact generally causes fractures of only one
leg on the side of impact

24. Head and face injuries
• Skull and facial bones fractures
commonest hinge fracture of base, linear fractures of vault and
localised comminuted fracture of skull bones and fractures of facial
bones
• Brain injury
DAI/DVI; focal contusions and laceration of cortex with patchy SAH
, SDH
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25. Neck injuries
•Disruption of atlanto-occipital joint: rapidly
fatal and due to combination of extension ,
rotation and post movement of head on the
spine, associated with severing of spinal cord
or brain stem
•Fracture dislocations of cervical Vertebrae
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26. Chest injuries
•Surface injuries
•Rib fractures: tearing of pleura &
intercostal vessels
•Lungs: contusion and laceration.
•Cardiac injury
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27. Abdominal and pelvic injuries:
•Liver: Lacerations or right lobe crushed
if impact is at lower part of chest.
•Mesentery, spleen and kidneys:
lacerations occur.
•Separation of pubic Symphysis or
undisplaced fractures of pubic rami
•Dislocation of sacro-iliac joint
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28. Trace evidence and Toxicology in
pedestrian deaths
•Trace evidence may become a critical factor in linking
a victim with a vehicle , as in hit –and –run death
•On vehicle , hair, skin and blood from victim deposited
on vehicle at the time of impact .
•Broken windshield glass may retain a strand of hair or
fabric
•On victim-paint, chip, tire marks or grease from the
undercarriage
•Toxicology: alcohol and or drugs.

29. Motor cycle deaths
•Head impact may cause severe angulation of
neck, with resultant neck injury , such as
atlanto-occipital fracture separation
•When passenger fall off of motorcycles, they
tend to fall backward, incurring posterior scalp
lacerations, fracture of posterior skull( basilar
fossae )and contre-coup brain contusions.
•Motor cyclist may drive into the back of large
vehicle e.g. truck , known as “under-running
or tail- gating”
• Head and shoulders are smashed against the tail
board , even decapitation may occur.

30. Bicycle ( pedal –cycle injuries)
• If bicyclist is struck by a motor vehicle , injuries may be
primary ( from the impact) , or secondary ( impact with ground)
• Degree of injury is most dependent on the speed at which speed
takes place
• “Bicycle spoke injury” is a specific injury which may occur
when a rider or passenger on a bicycle slips from the seat or
handlebars , causing the foot or leg to pass through the spokes
of the wheel.
a. usually involves a child
b. soft tissue of lower leg is crushed , with internal
avulsion or damage

31. Causes of asphyxial deaths related
to motor vehicles
•Crush asphyxia
•Gas inhalations :Co, N2O
•Positional asphyxia
•Hanging : from seat belts
•Choking /suffocation :aspiration of blood from
craniofacial trauma; inhalation of soil after a vehicle
crash; facial compression
•Drowning : entrapment in a submerged vehicle
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32. Causes of death in MVA
Immediate/within few hours
1. Heamorrhage ( immediate or delayed)
2. Fat embolism
3. Pneumonia
4. Carbon monoxide poisoning
5. Fire
Delayed deaths : from complications of trauma like
progressive brain damage, ARDS,
bronchopneumonia , delayed haemorrhage from
liver and spleen and thrombo-embolism
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33. Investigation of automobile accidents
Should include
•1. Study of accident scene: skid marks, tyre marks etc
•2. Mechanical and engineering exam. of involved
vehicles and each of component whose failure could
affect safety in motion
•3. Complete autopsy of all dead victims
•4. Physical and psychiatric exam of surviving drivers
•5. Personal and social histories of surviving persons
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34. The autopsies are performed to
•Determine the cause of death
•Confirm that death was caused by injuries suffered /
sustained in the accident
•Determine the extent of injuries
•Detect any disease or factor e.g drugs that could have
precipitated or contributed to the accident or death
•Detect any criminal activity associated with death
•Document all findings for subsequent use in either
criminal or civil actions
•Establish positive identification of the body, especially
if it is burnt or severely mutilated
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35. Autopsy :
1.Examination of clothes : look for trace
evidence/ physical evidence , tyre marks etc
2.External and internal examination of body:
look for primary impact , secondary injuries on
the body ; Neck dissection & extremity dissection
3.Cause of death determination : role of
disease and accidents ; drugs and accidents /
drunken driving ; psychology and accident
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