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Forensics

Motor vehicle deaths


Author: Lindsey Harle, M.D. (see Reviewers page)
Revised: 16 August 2012, last major update August 2012
Copyright: (c) 2012, PathologyOutlines.com, Inc.

Types of collisions
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Frontal impact:
● Most common (80%); occurs when two vehicles collide head-on, or when a single vehicle hits a stationary object head-on
● Vehicle occupants continue moving forward due to kinetic energy; impacting the windshield and dashboard
● Drivers show trauma of the anterior head due to impact with windshield or visor; may show skull fractures, atlantooccipital dislocation, neck fractures, diffuse axonal injury
● Drivers may have chest injuries due to impact with the steering wheel, with sternal and rib fractures, pulmonary contusions and lacerations (due to rib fractures), cardiac laceration/contusion, aortic dissection, hepatic and splenic lacerations
● May show pattern impact injury of the steering wheel
● Drivers may show wrist or forearm fractures if hands were positioned on wheel at time of impact
● Drivers may have patellar or femoral fractures due to impact with dashboard; or ankle fractures
● “Dicing injuries” to the left face and left arm: small abrasions/lacerations on driver due to shattering of the driver-side window
● Front seat passengers: injuries similar to driver, but no steering wheel impact
● Dicing injuries of the right face and right arm due to shattering of passenger side window
● Unrestrained rear passengers may be thrown to front compartment of vehicle

Side impact:
● Usually due to one vehicle impacting the side of another vehicle
● All injuries seen in frontal impact collisions can occur
● Injuries should be more severe on side of impact; individuals on impacted side should have more severe injuries than those on the opposite side

Rear impact:
● May cause “acceleration” injuries (e.g. whiplash) which tend to be less severe

Rollover:
● Tend to be more severe; many different injury patterns can occur
● May cause traumatic asphyxia if individual is ejected and becomes trapped beneath vehicle
● May see pattern injury from seatbelts; pattern should correspond to position of individual in car (e.g. driver vs. passenger)
● Seatbelts can produce mesenteric, omental, or bowel contusions/lacerations

Suicidal motor vehicle accidents
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● Vehicle directly collides with fixed object or another vehicle
● No signs of braking at scene
● Decedent may have history of suicidal ideation or suicide attempts

Pedestrian deaths
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Factors influencing injury pattern:
● Vehicle speed: high speed impact may cause pedestrian to be thrown over vehicle
● Braking may result in pedestrian being “picked up” by vehicle or being thrown forward
● Type of vehicle: larger vehicles that hit pedestrian above their center of gravity tend to knock them down rather than pick them up
● Size/age of pedestrian: impact below pedestrian’s center of gravity causes them to be lifted and thrown

Injuries sustained by pedestrians:
● Tire/tread marks: on skin or clothing; can link pedestrian to vehicle
● Pattern injuries: in addition to tire marks, can include impressions of bumper, headlights, or other parts of vehicle; can be used to link pedestrian to vehicle
● Bumper fractures: occur when bumper strikes pedestrian’s lower extremities; may not be associated with overlying cutaneous injury
● Measure distance from heel to estimate bumper height
● Contusion pockets: collections of blood in subcutaneous tissue or muscle; due to impact with hood or bumper
● “Stretch” lacerations of inguinal folds: due to overstretching of body at hip joint; appear yellow and dry
● Suicidal pedestrian deaths: need witness information and decedent history of suicidal ideation to corroborate

Motorcycle deaths
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Types of injury:
● Head trauma: most common lethal injury; may occur even in individuals wearing a helmet
● Basilar skull fracture is most common
● Motorcycle passengers tend to fall backwards, producing lacerations and fractures of posterior head
● Brush abrasions (“road rash”) on exposed skin
● Traumatic asphyxia: may occur if motorcycle lands on individual

Bicycle deaths
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● Most bicycle accidents produce only minor trauma
● Degree of injury is largely related to speed of the impact
● Bicycle spoke injury: occurs when leg or foot passes through wheel spokes; causes crushing/avulsion of soft tissues; more common in children

Evidence to examine
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● Toxicology of driver, passenger, and pedestrian, to include carbon monoxide for vehicle occupants
● Trace evidence: hair, blood, clothing fibers, glass chips, or paint chips can be used to link a car to a pedestrian death, or to determine a person’s position in vehicle

End of Forensics > Motor vehicle deaths


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