Medico-Legal Investigations
Blunt Force Trauma
Blunt Force Trauma
 There are Four Main Divisions of Blunt
Force Type Injuries. They are:
– Abrasions or scrapes: scratches and grazes
– Contusions (leakage of blood from vessels =
extravation) or Bruises
 Extra = outside; vasa = vessel
– Lacerations or Tears
– Fractures of Bone(s)
Blunt Trauma
 The severity of blunt
trauma depends on:
– Amount of force
delivered
– Time over which the
force is delivered
– Region struck
– Extent of body surface
struck
– Nature of the Weapon
Blunt Trauma Wounds
 If a weapon breaks on impact less energy is
delivered to the body
 If the body moves with the blow less energy
is delivered to the body
Blunt Trauma Wounds
 The larger the area over which the blow is
delivered the less severe the injury
 An object that projects from the weapon will
deliver all of the force
 Rounded portions of the body can sustain
greater injuries
Blunt Trauma Wounds
 Abrasions:
– An injury in which there is removal of outer
layers of tissue by compression or a sliding
force
– Indicates EXACT site of contact or impact
– In living persons the wound will scab over and
become dry and darken
– Postmortem the wound is yellow with a
parchment-like appearance
Blunt Trauma Wounds
 There are three types of Abrasions:
– Scrapes
– Impact
– Patterned
What is the Forensic Significance of
Abrasions?
 Indicates violence
 Its shape gives an idea about the causal
instrument
– Bite abrasions take the pattern of the teeth
 Site of abrasion denotes the type of crime
 Age of abrasion can be estimated so the time of
the incident is known
 Helps in identification of the assailant as in bite
abrasion
Blunt Trauma Wounds
 Scrapes
– A blunt objects takes off the
top layers of skin
– May go as deep as the
dermis
– Leakage of fluids
(serosanguineous fluid)
– The area is reddish brown
and forms a scab
BFT
Blunt Trauma Wound
 Impact Abrasions
– The blunt force is perpendicular to the surface
of the body
 Mostly seen over bony process
– Eyebrows
– Cheekbone
– Nose
BFT
Blunt Trauma Wound
 Patterned Abrasions
– This occurs when the
object which impacts
the body leaves an
imprint or stamp on the
skin
– Be aware postmortem
insect bites may
resemble patterned
abrasions
Blunt Trauma Wound
 Dating Abrasions is a complicated process
– Scab formation begins in 4-6 hrs and is usually
complete in 18 hrs
– The skin begins to regenerate within 72 hrs
– Once the scab falls off the skin will remodel and
become thinner after about 12 days
What is a Contusion?
 Bleeding under intact skin due to heavy
blunt instrument
– Hemorrhage into the skin, the tissues under the
skin or both
– Caused by crushing or squeezing of tissue
Can you Differentiate Ante- and
Postmortem Contusions?
 Yes,
 Ante mortem
– Swelling present
– Color change
– Not washable
– More tissue infiltration (diffuse)
Blunt Trauma Wound
 Contusions (Bruising)
– Leakage from ruptured, injured or traumatized
blood vessels (cellular leakage as well)
– Diffuses out into surrounding tissues
(hematoma)
– Sufficient BFT must have been applied to tear
one or more vessels
Blunt Trauma Wound
 Fresh Bruises & Trauma:
– Age and color a bruise presents depends on certain factors
– Bruises can vary in color (depending on person)
 Age (Children and elderly bruise easier)
– A bruise can appear or disappear depending on:
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Oxygen levels
Blood pigment & breakdown of hemoglobin
Physical Health Antemortem
Localized area of injury
cancer leukemia
scurvy
Aspirin
Anticoagulants (cumadine, heparin, warfarin, etc.)
Temperature
Hemophilia
Blunt Trauma Wound
 Bruising
– Bruises can formulate easier in:
 Loose tissue
 Fat
 Older adults and/or children
 Women (less muscle mass)
 Disease of the vascular system
Blunt Trauma Wound
 Dating Contusions:
– This is not an exact science
 Hemosiderin in macrophage
 Bruises usually follow a
color pattern but not always
– Reddish-purple or
bluish-purple to violet,
green, dark yellow to
greenish-yellow and
then disappears
– The edges of the bruise
have the oldest colors
Blunt Trauma Wound
 Bruising
– May take minutes to
days to present
 Take photograph
incrementally during this
time
– Bruises can mask
natural color
– Estimation of age of
bruise can be difficult
after death
BFT
BFT
What are the Diagnostic Features of
Lacerations?
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Bridging
Abraded Edges
Edges irregular
Contusions at edges
Hair crushed
Blunt Trauma Wound
 Lacerations (Tears):
– Tears in the skin due to pressure (BFT) are
called lacerations
– Lacerations are distinguished from incisions by
“bridging”
– Lacerations may or may not imprint the object
used to create BFT
– There may be no external signs of injury but
avulsions may occur
Blunt Trauma Wound
 Lacerations
– The wound usually has
ragged or abraded edges
– Wound margins are
irregularly shaped
– BFT injuries often contain
evidence (trace) embedded
in wound
 Paint, bark, fibers,
grease, metals, rubber,
etc.
– May be scrapes and bruising
around the wound as well
Blunt Trauma Wound
BFT
BFT
BFT
Blunt Trauma Wound
 Defense Wounds due to BFT
– Mainly abrasions and contusions
 On back of hands, wrists, forearms
Blunt Trauma Wound
 Fractures of Bone
– Can determine “directionality” of the impact
– Can present as clear breaks
– Can present as compound fracture
– Can present as hair-line fracture
Blunt Trauma Wound
 Fractures of the
Extremities
– Direct Force
 Blunt object impacts a
long bone causing
breaking of the bone on
the opposite side of
impact
 May be crushing on side
of impact if force is great
enough
Blunt Trauma Wound
 Direct Force
– Penetrating Fractures
 Large force acting
on a small area
– Gun shot wounds
– Focal Fractures
 Small force on a
small area
– Bat or pipe
Blunt Trauma Wound
– Crush Fractures
 Large force over a
large area
– Motor vehicle
(bumper
fractures)
Blunt Trauma Wound
 Indirect Force
– Produced by a force acting at a distance from
the fracture site
Blunt Trauma Wound
 Indirect Fractures
– Traction Fractures –
bone is broken by a
violent contraction
– Angulation Fractures –
bone is twisted (spiral
fracture)
– Verticle compression
Fractures – oblique
fracture of long bones
BFT
Case Study
 An elderly woman was discovered lying on her
back in her sewing room. Rigor mortis was in its
early stages. A prominent amount of blood was
covering her face. At autopsy there were red-blue
contusions to her chest and right side with
associated lacerations of the spleen and liver.
After washing her face, a patterned contusion of
the left cheek was noted resembling a heel mark
from a shoe or boot. There was no significant
head trauma.
Case Study
 Numerous photographs of the facial contusion was
taken.
 Within hours of the autopsy, a suspect was
apprehended. He was present in the
neighborhood the last day the woman was seen
alive. He was wearing tennis shoes which the
authorities confiscated for testing. Fingerprint
powder was dusted on the soles.
Case Study
 A transparency print was made, and the
transparency was placed over the photograph of
the facial wound. A criminalist determined the
comparison was a positive match and the
pathologist agreed. On the basis of these
examinations the suspect was indicted. No other
incriminating evidence was found against him.
Should these interpretations have been made?
Was there enough information to indict? If not
what other evidence would you want them to
collect?
Case Discussions
 The approach by both the pathologist and
criminalist were sound. Both looked at the shoes,
transparency and photograph of the wound to
make comparisons. A mark on the face can be
matched with an offending weapon if the pattern is
distinct. In this case, both examiners thought the
match was perfect because the marks on the face
corresponded to the depressed areas of the heel
of a shoe.
Case Discussions
 Matching patterns on a body with objects
that may have inflicted them is an important
part of examining injuries caused by blunt
trauma. These patterns, however, cannot
be used to determine whether a specific
weapon inflicted injury.
Case Discussions
 At best one can determine that a weapon of
similar dimension caused damage. Although
patterned injuries on the body are not commonly
matched to a particular weapon, there may be
other material transferred from a victim to a
weapon such as hair, fibers and blood. Thus, the
examination suggested that the mark was made
by a boot with a certain type of sole.