Lecture Notes in Forensic Medicine
© Derrick Pounder, University of Dundee
- 1 -
BLUNT FORCE INJURIES
A wound is a disruption of the continuity of tissues produced
by external mechanical force. The term injury is used
synonymously with wound, but can have a wider meaning and
encompass not only damage produced by physical force, but
also damage produced by heat, cold, chemicals, electricity and
radiation. The English word ‘injury’ derives from the Latin
word ‘injuria’ which literally means not lawful. The term
lesion originally meant an injury but has now come to be more
widely applied to include any area of injury, disease, or local
degeneration in a tissue causing a change in its function or
structure. Therefore use of the terms injury or wound imply
damage from unnatural causes, while the use of the term
lesion is non-committal on whether the cause of the damage
was natural disease or not.
Wounds, or injuries, are generally classified according to their
cause as blunt force injuries, sharp force injuries, gunshot
injuries, and a miscellany of others, including for example
burns. This is the classification followed in this text, and each
group of injuries is discussed in successive chapters.
A blunt force injury is any bodily damage resulting from
forceful contact between the body and a blunt object. The
forceful contact most commonly involves movement and
impact, with the resulting transfer of kinetic energy. Either the
moving object strikes the body as in a blow, or the moving
body strikes an unyielding object as in a fall. Less often the
physical force is applied more slowly by the pressure of
crushing, squeezing, or pinching. Crushing or scraping of the
skin produces abrasions (grazes).
Bruises occur when the
elastic limit, the tolerance, of subcutaneous blood vessels is
exceeded so that they tear and bleed.
Greater forces are
needed to tear the skin to produce lacerations. These three
blunt force injuries – abrasions, bruises, and lacerations – may
occur singly or together in any combination.
An abrasion is an area of crushing or loss of skin, or mucous
resulting from contact with a blunt object.
Abrasions are typically superficial, trivial injuries which may
be overlooked easily but provide useful forensic information.
They bleed only slightly, heal quickly and leave no scar.
Tangential impact between an object and the skin causes a
typical graze in which the superficial skin layers are scraped
off and piled up as skin tags at the far end of the injury. The
location of the skin tags indicates the relative direction of
movement between the object and the body.
Broad patches of abrasion are sometimes described as brush
abrasions, the frictional element of which gave rise to the term
‘brush burns’, as in for example ‘carpet burns’. They are seen
in their most florid form as ‘road rash’, following a motor
vehicle collision in which the victim, typically a motorcyclist,
slides along the road surface.
Trace evidence from the impacting surface may be present