Mechanical momentum means mass with
velocity discharged into the human body by a moving object or weapon or itself
due to impact of moving body against a surface produces injuries over the body.
In the first case, the counter force is provided by the body and in the second
case, by the rigidity of the object/weapon/surface/wall against which the victim
falls by himself or is forced to fall by external reason. In most cases it is
seen that the mechanical injuries produced over the body are due to a
combination of above two forces. Abrasion is one of the most superficial
injuries and involves destruction of the superficial layers of the skin, caused
by fall on a rough surface, or being dragged by a vehicle. Abrasions are of
different types based on the pattern of the causative force viz. scratches,
grazes, pressure, impact or imprint abrasions. A doctor can help legal
investigation by his evaluation and documentation of abrasions as below.
- They give an idea about the site of impact and
direction of the force.
- They may be the only external signs of a serious
internal injury.
- Patterned abrasions may help in relating the wound to
the object which produced them.
- The age of the injury can be determined, which helps to
corroborate with the alleged time of assault.
- Dirt, dust, grease, sand in the open wounds may connect
the injuries to the scene of crime
- Character and manner of the injury may be known from
its distribution.
- In throttling, crescent abrasions due to fingernails
are found in the neck
- In smothering, abrasions may be seen around the mouth
or nose.
- In sexual assaults, abrasions may be found on the breasts,
genitals, inside of the thighs, and around the anus.
- Abrasions on the face of the assailant indicate a
struggle.
- Abrasions on the victim may show whether the
fingernails of the assailant were long, irregular or even broken.
