MECHANICAL INJURIES

all you want to know about mechanical injuries ..its types etc.

1. MECHANICAL
INJURIES

2. INTRODUCTION
An injury is define as any harm, whatever illegally
caused to any person in body, mind, reputation or
property as per Indian Panel Code (Sec. 44). In
forensic science, the injuries/wounds are
produced by physical violence, which break of the
natural continuity of any of the tissues of the
living body .There are different types of injuries.
Trauma is explained as an injury to the body
caused by physical, mechanical or chemical
factors, which may result in wounds or possible
complications. The medical purposes, violence
refers to either behaviour that result in injury or
both psychological and physical trauma .

Mechanical trauma is an injury to any portion of
the body from a blow, crush, cut, or penetrating
wound.

3. MECHANICAL INJURY
General principles
A wound is caused by a mechanical force which may be
either a moving weapon or object, or the movement of the
body itself. In the first case, the counterforce is provided by
the inertia of the body, and in the second case by the rigidity
of some stationary object against which he falls.
A combination of these two events is seen in most cases. Due
to the impact between the forward moving force and the
counterforce, energy is transferred to the tissues of the body,
which causes a change in their state of rest or motion. The
human body contains many complex tissues which greatly
vary in their physical properties, such as state of solidity,
fluidity, density and elasticity, and because of this a change in
the state of rest or motion of the body produced by a forceful
impact does not affect the tissues uniformly. Some of the
energy is spent in moving the body as a whole. But most of
the energy may cause non uniform motion of localised parts
of the body, due to which the affected tissues will be
subjected to compression or to traction strains or to a
combination of both. All the body tissues, except those which
contain gas, are resistant to compression, i.e., they resist
force tending to reduce their· volumes. Mechanical force
does not cause compression of the tissue but causes their
displacement and deformation, and traction strains are
produced in the affected tissues. Such strains may be due to

4. forces causing simple elongation of tissues, but they may be
due to more complex mechanism, such as bending, torsion or
shearing.
The complications of mechanical trauma are usually related
to fracture ,haemorrhage and infection. They do not
necessarily have to appear immediately after occurence of
the injury. Slow internal bleeding may remain masked for
days and lead to an eventual emergency. Similarly wound
infection and even systemic infection are rarely detectable
until many days after the damage. All significant mechanical
injuries must therefore be kept under observation for days or
even weeks.

FACTORS INFLUENCING THE NATURE AND EXTEND OF WOUND
1. The Nature of the Object or Instrument:
With a blow from a pointed or sharp-edged weapon,
the force is concentrated over a limited area; due to
which deep penetration or incision of the tissues occurs.
The hardness of the tissues and the friction of the
divided tissues against the sides of the object resist the
passage of object through tissues. With a blow from a
blunt instrument, the force is distributed over a
relatively large area, due to which the damage caused to
a unit mass of tissue is less than when the force is
concentrated over a smaller area.
2. The Amount of Energy Discharged During Impact:
The amount of kinetic energy present in a moving
object is measured by the formula mv2/2, where m =

5. mass, and v= velocity of the moving object. An object of
definite weight moving at a definite speed produces a
definite amount of energy. If the weight of the object
alone is doubled, the kinetic energy is doubled, but if
the velocity only is doubled, the kinetic energy is
quadrupled. Therefore, the velocity of the object is
more important than the weight.
3. The Conditions under which the Energy is Discharged:
Most of the energy liberated in an impact may he
spent in causing generalised movements of the body,
which may be sufficient to knock down a person,
although the local injury may be minimal. If the body or
part of the body struck is immobilized, the greater part
of the kinetic energy may be spent in causing localised
deformation. If the head is free to move, a blow may
cause little damage, but if the head is well supported, a
similar blow may cause marked injury to skull.
4. The Nature of the Affected Tissues:
Skin: The shape of the skin is readily changed when
struck as it is very pliable and a little elastic. The skin is
strongly resistant to traction forces due to the firm
coherence of its tough layers of keratinized cells, and it
is often not damaged when struck with a blunt
instrument, though the underlying tissues may be
damaged severely. When crushed against rigid bone, the
skin is readily split.
Subcutaneous Tissues: The subcutaneous tissues are
very plastic due to their fat content and the pliability of
their' supporting connective tissue fibers.
Muscles: The muscles are usually not damaged from
blows due to their great plasticity and elasticity but may

6. be crushed or torn against bone or lacerated by
fragments of displaced and broken bone
Bones: The bones are relatively rigid. The bones may
bend without breaking when a force is applied, and then
may recoil to its normal shape due to its elasticity. A
blow to the chest may bend the ribs without fracture,
but the thoracic organs may be damaged. Fracture
occurs when the bone is bent beyond the limits of its
elasticity, which starts at the point of maximum
convexity caused by the bending.
Body Fluids and Gases: Fluid is incompressible but is
easily displaced. Powerful hydrostatic forces may be
produced in a hollow organ which contains fluid due to a
blow, which are transmitted equally and uniformly in all
directions and may rupture anatomically distant and
mechanically weak tissues.

7. CLASSIFICATION

Mechanical injuries are classified into

1. Abrasions
2. Contusions
3. Lacerations
4. Incised wounds
5. Stab wounds
6. Fire arm wounds
7. Fractures and dislocation

1. ABRASION
An abrasion is a destruction of the skin, which usually
involves the superficial layers of the epidermis only. They are
caused by a lateral rubbing action by a blow, a fall on a rough
surface, by being dragged in a vehicular accident, fingernails,
thorns or teeth bite. Some pressure and movement by agent
on the surface of the skin is essential. In its simplest form, the
epidermal cells are flattened and their nuclei are elongated.

8. If sufficient friction is applied, partial or complete removal of
the epithelium may occur and the superficial layer of dermis
is damaged.
CAUSATIVE AGENT
Hard blunt or hard blunt and rough or pointed end of an
object or weapon. Example: stone, stick, needle or any other
weapon or rough surface of any other material.
MODE OF PRODUCTION
Abrasions are produced by the impact of the above
materials, when friction is caused between the object and
the epidermis due to the impact. The direction of force
causing the friction may be horizontal (as in scratches or
grazes)or tangential or it may be more or less
perpendicular (as in pressure or imprint abrasion)
FEATURES OF ABRASION
Abrasions are superficial injuries. But often there is
accompanying injury to the subcutaneous or still
deeper tissues. At the site of abrasion, there may be oozing
of lymph and sometime very slight oozing of blood. The
lymph or blood which oozes out, and the denuded epithelial
debris , dry up within a few hours to form a scab. Abrasions
heal without formation of permanent scars.
TYPES
1. SCRATCHES
2. GRAZES
3. PRESSURE ABRASIONS

9. 4. IMPACT ABRASIONS
MEDICOLEGAL IMPORATANCE


1. From abrasion, the type of the weapon used, can be
said.
2. From linear or graze abrasion, the direction of
application of force and the relative position of the
victim and the assailant can be known.
3. From abrasions, time of assault can be roughly
assessed. When fresh, an abrasion is red with
evidence of oozing of serum and a little blood .By 8-
24 hours, there is a reddish scab formation. By 6th
day, it is blackish and it starts falling off from the
margins

4. Abrasions sometime give indication about the specific
type of offences committed. Nail scratches in the neck
of a dead body may be indicative of manual
strangulation or throttling may be indicative of killing by
smothering.

5. Abrasions may be produced on the vulnerable sites of
the dead body during shifting of the body to the
mortuary. These postmortem abrasions may be
mistaken as antemortem abrasions . These abrasions
are present mostly against the vulnerable bony
prominences.

10. Ante-mortem and Post-mortem Abrasions:
Abrasions produced slightly before or after death cannot
be differentiated even by microscopic examination. In
superficial lesions or when decomposition is advanced,
differentiation is difficult. After death, the abraded
epidermis becomes stiff, leathery, and parchment-like,
brown, more prominent, and may be mistaken for
burns. On drying, abrasions become dark-brown or even
black. In a body recovered from water, abrasions may
not be seen on first inspection, but they are easily seen
after the skin dries. Abrasions may be produced after
death when a body is dragged away from the scene of
crime. The distribution of such abrasions depends upon
the position of the body while it is being dragged.

2. bruise/ contusion
Features of bruise

When fresh a bruise is reddish in color, slightly raised
above the surrounding area, is painful and tender and
may or may not have denudation of the covering cuticle
.Gradually, it changes in color and subsides by two
weeks. It is usually roundish or takes the shape of the
striking part of the weapon. Along with rupture of the
capillaries. There is damage in the soft tissue. But the
skin is usually spared because skin tissue is quite tough

Type of weapon

11. Impact with hard blunt weapon produces bruise.
Example- stone, stick. Impact by a stick or rod will cause
two parallel linear bruises along the two margins of the
impact, with a pale gap intervening, the breadth of
which correspond with the diameter of the stick.
From this kind of bruise, the type of the weapon used,
can be known.
FACTORS WHICH INFLUENCE THE FORMATION AND
APPEARANCE OF A BRUISE

1. Quantity of force used- A greater force is more likely
to cause a bruise.
2. Quality of force- A hard blunt force will cause a
bruise, but a soft blunt force may not. Thus, striking with
a stone will produce a bruise, but covering the part of
the body with a rug before hitting with a stick may not
produce a visible bruise. No bruise may be apparent
externally, because the impact being soft, there may not
be any rupture of capillaries underneath the skin.
But it may cause deep bruise or haematoma adjacent
to the bone because, the applied force causes the soft
tissue to strike the hard bone, resulting in the rupture
of the capillaries and venules there.
3. Site of application of force
A greater force may even not produce any bruise on
the anterior wall of the abdomen due to toughness
and yielding force absorption capacity of the tissue there .But

12. bruises are easily produced against a bony prominence, say
malar prominence because the capillaries in the
subcutaneous tissue rupture easily in between the bone
underneath and the hard blunt force applied on the surface.
4. Sex
Females bruise easily due to delicacy of tissue in them
including the vessels, and also due to more subcutaneous fat
in them. Vessels present in the fatty tissue are more likely to
be ruptured on application of force than the vessels present
in the tough fibro muscular tissue.
5. Age
Infants, young children and very old persons
bruise more easily than young adults. In infants and young
children, it is due to delicacy of tissue including vessels and
more amount of subcutaneous fat.
6. Certain pathological conditions
Persons suffering from some disease (example- leukaemia
vitamin ”K” deficiency ),bruise easily without application of
much force. These persons may even develop haemorrhagic
spots without application of any force.
7. Complexion of the person
A bruise appears more prominent in a fair complexioned
person. In dark-skinned persons ,it may not be well
appreciated.
PATTERNED bruise

13. The design on the surface of the weapon maybe imprinted
on the bruise. Such a bruise is called a patterned bruise.
Example – bruises caused by a cycle chain
or motor vehicle grill. A bruise caused by the roundish end of
a weapon is circular in shape. When caused by the margin of
the circular end of the weapon, it is crescent shaped. If
caused by the body of a rod or stick then two parallel lines of
bruises appear with a gap in between , which is roughly equal
to the breadth of the weapon.

Medico- legal Importance:
1) Patterned bruises may connect the victim and the object
or weap, e.g., whip, chain, cane, ligature, vehicle; etc.
2) The age of the injury can be determined by color changes.
3) The degree of violence may be determined from their size.
4) Character and manner of injury may be known from its
distribution. (a) When the arms are grasped, there may be 3
or 4 bruises on one side and one larger bruise on the
opposite side, from the fingers and thumb 'respectively,
indicating the position of the assailant in front of, or behind
the victim.
(b) Bruising of the arm may be a sign of restraining a person.
(c) Bruising of the shoulder blades indicates rum pressure on
the body against the ground or other resisting surface.

14. (d) In manual strangulation, the position and number of
bruises and nail marks may give an indication of the method
of attack or the position of the assailant.
(e) Bruising of thigh especially inner aspect, and of genitalia
indicates rape.
(5) In the case of fall, sand, dust, gravel or mud may be found
on the body.
Bruises are of less value than abrasions because:
(1) Their size may not correspond to the size of the weapon.
(2) They may become visible several hours or even one to
two days after the injury.
(3) They may appear away from the actual site of injury.
(4) They do not indicate the direction in which the force was
applied
LACERATIONS

In laceration there is breach of continuity of tissue involving
depth more than the covering epithelium of skin or that of an
organ. Lacerations are caused due to impact by hard blunt
and rough weapons or objects.
Features

Shape – Usually irregular. Margin – Irregular. Floor – Tags of
tissue may be seen passing across the floor .Dimensions –

15. length or length and breadth both are more than the depth
of the injury .Foreign substances at the site of laceration –
Many of these injuries being sustained on roads or due to fall
etc., often the lacerations gave dust or such materials
adhered to their floors . These foreign materials
may sometime help to find out the place of occurrence of the
injury or assault
Types:
1) Split Lacerations: Splitting occurs by crushing of the skin
between two hard objects. Scalp lacerations occur due to the
tissues being crushed between skull and some hard object,
such as the ground or a blunt instrument.
Incised-like or Incised-looking Wounds- Lacerations
produced without excessive skin crushing may have relatively
sharp margins. Blunt force on areas where the skin is close to
bone, and the subcutaneous tissues are scanty, may produce
a wound which by linear splitting of the tissues, may look like
incised wound.
2) Stretch Lacerations: Overstretching of the skin, if it is fixed,
will cause laceration. There is localised pressure with pull
which increases until tearing occurs and produces a nap of
skin, which is peeled off the underlying bone or deep fascia.
This is seen in the running over by a motor vehicle, and the
flap may indicate the direction of the vehicle. They can occur
from kicking, and also when sudden deformity of a bone
occurs after fracture, making it compound.

16. 3) Avulsion: An avulsion is a laceration produced by sufficient
force (shearing force) delivered at an acute angle to detach
(tear oft) a portion of a traumatized surface or viscous from
its attachments. The shearing and grinding force by a weight,
such as lorry wheel passing over a limb may produce
separation of the skin from tile underlying tissues (avulsion)
over a relatively large area. This is called "flaying". The
underlying muscles are crushed, and the bones may he
fractured. The separated skin may show extensive abrasions
from tile rotating frictional effect of tile tyre, but one portion
is still in continuity with adjacent skin. Internally, organs can
be avulsed or torn off in part or completely from their
attachments.
4) Tears: Tearing of the skin and tissues can occur from
impact by or against irregular or semi-sharp object, such as
door handle of a car. This is another form of overstretching.
5) Cut Lacerations: Cut lacerations may be produced by a
heavy sharp-edged instrument. The object causing a
lacerated wound crushes and stretches a broad area of skin,
which then splits in the centre. The edges are irregular and
rough, because of tile crushing and tearing nature of the
blunt trauma. Frequently, the skin, at the margins is abraded
due to the flatter portion of the striking object rubbing
against the skin as it is indented by the forceful blow.
Medico-legal Importance:
(1) The type of laceration may indicate the cause of the injury
and the shape of the blunt weapon.

17. (2) Foreign bodies found in the wound may indicate the
circumstances in which the crime has been committed.
(3) The age of the injury can be determined.
INSICED WOUNDS

Incised wounds are cuts or slashes produced by the sharp
edge of a weapon like, knife, razor, sword etc.
Mode of infliction
By drawing or saw like movement of the weapon on the body
surface when the weapon is rather light like, a knife or razor
,by striking the sharp edge on the body when the weapon is
heavy or moderately heavy like, axe ,sword etc.

Features of incised wounds
1. Shape – The shape of an incised wound is elliptical or it is
spindle shaped. It maybe oval if the wound gaps much. .The
shape of the incised wound may change in its curvature due
to elasticity, creases and cleavages of the skin and the
direction of the underlying muscle.
2. Length of the wound - Length of an incised wound is
greater than breadth and depth. Length of the wound does
not correspond with the length of the blade of the weapon
when the incised wound is caused by
drawing or sawing. It may correspond when the wound is
caused by striking.

18. 3. Breadth – Breadth of an incised wound primarily depends
on the thickness of the effective part of the blade i.e., the
thickness of the blade at that level upto which the edge of
the weapon has gone in the tissue. But the breadth depends
much on the elasticity of the skin of the area and direction of
the fibres of the muscle underneath the skin, in relation with
the length of the wound. If the underlying muscle fibres
are cut across their length then, contraction or shortening of
the cut muscle fibres on both sides of the incised wound will
cause widening of the gap (bread) of the
wound.This does not happen if themuscle fibres not cut acros
s or if the fibres run along the length of the incised wound.
4. Angles - The angles at both ends of the incised wound is
sharply defined.
5. Margin – Margins of an incised wound are well defined,
cleanly cut and sharp.
6. Floor – Floor of the wound is also sharply cut and divided.
7. Haemorrhage – As the vessels are also sharply cut, there is
excessive external haemorrhage. If the haemorrhage is
from a vein then bleeding occurs in drops, which is stellate in
appearance. If it is from the arterial source, then there is
spurting effect and the bleeding occurs in jets
8. Hesitation cuts – These are also termed “tentative cuts”.
These are multiple superficial cuts placed around the
beginning part of the main wound, in cases of suicide. These
superficial tentative
or hesitation cuts indicate hesitation or indecisive state of

19. mind of the suicide, before he finally inflicts the deep fatal
wound on his own body.

9. Defence wounds :These are in most occasions , incised
wounds though abrasions; bruises, lacerations or punctured
wounds also may be sustained in defence for self protection.
Defence cuts may be present on the palmar aspects of the
hand if, when attacked with a sharp cutting weapon, the
victim holds the blade of the weapon to escape the assault.
In such a case there may be incised wounds on the palmar
aspects of more than one finger, but all of them are expected
to be in one line, if the blade of the weapon is single edged.
Medicolegal aspects of incised wound
1. Incised wounds are usually suicidal, then homicidal and
only occasionally accidental. Suicidal incised wounds are
usually placed in front and sides of the neck or sometimes in
front of the wrists, to cut the radial artery to bleed to die.
2. Direction of application of force – From the tailing
and bevelling, the direction of application of force can be
known.

3. Cause of death – In case of incised wound there is
excessive external bleeding. Death therefore in many cases
occur due to haemorrhage and shock. In case of cut-throat
injury ,death, in addition, may occur due to asphyxia due to
choking of the respiratory passage by blood.
CHOP WOUNDS

20. Chop wounds are
incisedwounds produced by striking withsharp cutting, heavy
or moderatelyheavy weapons, like axe, sword etc .These
wounds are comparatively deeper and broader than the
incised wounds produced by drawing or saw like movement
of light sharp cutting weapons Abrasions or contusions
maybe produced at the margins due to friction with the
surface of the thick and heavy blade. These wounds usually
have bevelling also. Bevelling – When a sharp cutting heavy
or moderately heavy weapon is used (striking) tangentially or
a tan angle to the body, then there is flapping at one margin
of the wound at the cost of the other margin.
STAB WOUND

Punctured or stab wounds are deep wounds produced by the
pointed end of a weapon or an object , entering the body
.Depth is the greatest dimension of punctured wound
Causative Weapon : Punctured wounds may be caused by the
tip of a knife, arrow, needle. Punctured wounds may also be
caused by an object or weapon having no pointed end, e.g.,
blunt end of an iron rod. The pointed weapon may or may
not have sharp edge. Example: spear (have pointed end but
may or may not have sharp edge), needles (have pointed end
but no sharp edge), end of an iron rod (not pointed or sharp
edged)
Varieties of punctured wounds

21. 1. Perforated Wound
Here part of the weapon passes through the whole thickness
of any part of the body, e.g. when the tip of a weapon enters
the body through anterior surface of the chest and exits out
through the posterior surface of the chest. In a perforated
wound there will be two outer or external wounds with a
single strike,(a) wound of entrance, the wound through
which the weapon enters the body and(b)wound of exit,
through which the tip of the weapon comes out of the body

2. Penetrated wound. Here the wound terminates inside a
body cavity or viscous , e.g. penetrating wound ending inside
the abdominal or chest or cranial cavity.3. Punctured or
stab wound without causing penetration to a body cavity
or without perforating the whole thickness of the body. Here
the tip of the weapon terminates inside the body except in a
body cavity
Features of punctured wounds

1. Shape The shape of the wound of entrance in case of stab
wound depends mostly on the shape of the weapon or shape
of the edge of a weapon.
When a double edged pointed weapon is used , the external
wound is elliptical, spindle shaped or slit-like in appearance.
In spindle shaped or elliptical wounds produced by double
edged weapon, both the margins and angles will be sharp,

22. clean and well-defined. When a single-edged pointed
weapon is used, the external wound will be triangular
or wedge-shaped. In wedge-shaped wounds produced by
single-edged pointed weapons two margins and one angle
will be sharply defined
2. Margin: When stabbed with double-edged sharp cutting
pointed weapon, both the margins of the elliptical external
wound will be clean cut ,regular, sharp and well defined.
When caused by a single-edged sharp cutting pointed
weapon, the wedge shaped external wound will have two
long, clean cut, regular, well defined margins with one short
irregular margin. When caused by pointed or blunt ended
weapon without any sharp edge, then the margin will be
irregular, uneven with abrasion ,contusion and even tears
3. Depth : Depth is the greatest dimension of a punctured
wound. The depth of the wound usually depends on the
length of the weapon or the blade of the weapon upto which
it enters in the body. If the whole length of the blade of the
weapon enters the body, then surrounding the wound of
entrance there will be a contusion or abrasion due to friction
or pressure by the hilt or blade-guard of the weapon.
If the whole length of the weapon does not enter the body
then, there will not be any hilt mark in the form of abrasion
or bruise. In such cases, the depth of the wound will not
correspond with the length of the blade of the weapon.
Similarly, in case of a perforated wound, when a part of the
weapon comes out through the wound of exit, the depth of
the wound will not give the length of the blade of the

23. weapon even though, hilt mark may be present around the
wound of entrance indicating that, whole length of the blade
has passed through the tissue.
4. Hilt mark: Most of the sharp cutting pointed weapons have
a hilt or hand guard in between the butt and the blade, so
that, during use the hand will not slip down over the blade of
the weapon and get injured .When in a stab wound, the
whole length of the blade is pushed inside the body then the
hilt strikes against the skin around the wound of entrance
and keeps its mark over there in the form of abrasion or
occasionally in the form of bruise. Thus, hilt mark has
two importances. If there is abrasion due to hilt around the
wound, we can say that, that wound is the wound of
entrance and that the whole length of the blade of the
weapon was pushed inside the body and the weapon has a
hilt
5. Haemorrhage: In case of stab wound internal haemorrhage
is more than the external haemorrhage due to injury to
internal vessels. The extent of internal haemorrhage may not
be guessed until the body is dissected open.
6. Injury to the internal organs: In stab wounds, injury to
the vital internal organs is more common and is the real
danger. Stab wounds over the head, neck, chest or abdomen
are obviously more dangerous due to possible injury to the
vital organs
7. Examination of punctured wounds require extra vigil,
because, these wounds have greater depth which cannot be
examined from outside and because, punctured wounds are

24. expected to cause injury to the vital organs of the body
and extensive internal haemorrhage. The depth and direction
of the track of the wound should not be attempted from
outside with the help of a probe. Such an attempt may cause
further extension of the depth or extension in a new
direction during probing.
Medicolegal importances of stab wounds

1. About the nature of the injury: Generally speaking, stab
wounds are most commonly homicidal, next in occurrence
suicidal and lastly accidental.
Homicidal stab wounds are usually more than one in number,
all are quite deep ,may be located anywhere on the body
,including self unapproachable parts. In homicidal cases, the
covering clothes usually bear corresponding cut marks
or tears. Defence wounds and marks of resistance may be
present on the body .Foreign materials like foreign scalp hair
or shirt-button etc. may be found in the
tightgrip of the hand of the victim in a state of cadaveric spas
m. The weapon of offencemay not be available on the spot.
Suicidal stab wounds are located on the approachable parts
of the body, more commonly over the left side front of chest,
neck and
lower abdomen. The main wound maybe only one. The cover
ingclothes may not bear corresponding cut marks as that may
be partly removed from the area while doing the act. The
weapon may be held in the hand in
a state of cadaveric spasm, or it may be present near death.

25. No defence wounds or marks
of resistance will be present on the body, but some self-
inflicted incised wounds may be present on the other
approachable parts of the body. The place of occurrence will
not be disturbed and it may be a secluded place, not
approachable to others. Sometimes a suicidal note may be
left behind by the suicide. In some cases the suicide might
have tried some other method before stabbing himself to
death .Evidence in support of this may be present on the
body.

2. From the shape and size of the external wound and the
depth, the type of the blade of the weapon used can be said.


FRACTURES
Fractures may be caused by direct or indirect violence.

1. Fissured fractures: These are linear fractures of cracks in
the bone involving the whole thickness of the bone or one or
the other table only. They are caused by forcible contact with
a broad resisting surface like ground , blows with an agent
having a relatively broad striking surface or from a fall on the
feet or buttocks.The fracture starts at the point of impact and
runs parallel to the direction of the force. If the head is
supported when struck, the fracture may start at the counter

26. pressure. The fracture line tends to follow a devious course
and is usually no more than hair’s breadth.
2. Depressed fractures: in this portions of fractured bones are
driven inward into the skull cavity. Their pattern often
resembles the weapon or agent which caused it.They are
caused by blows from heavy weapons with a small striking
surface eg; stones , sticks, hammer.
3. Comminuted fractures : In this the bone is broken into
several pieces . They are caused by a fall from height , vehicle
accidents and from blows by weapons with a large striking
surface, eg; heavy iron bar, axe, thick stick. Fissured fissures
may radiate for varyind distances from athe area of
comminution.
4. Pond or Indented fractures : This is a simple imbucklingof
the skull which results from the obstetric forceps blade, a
blow from a blunt object or forcible impact against some
protruding object.
5. Gutter fractures : They are caused when part of the
thickness of the bone is removed so a s to form a gutter , eg;
glancing bullet wounds . They are usually accompanied by
irregular depressed fractures to the inner table of the skull.
6. Ring or foramen fractures: It is fissured fracture which
encircles the skull in such a manner that its anterior third is
separated at its junction with the middle and posterior
thirds.But usually the term is applied to a fracture, e=which
runs about 3 to 5 cm.outside the foramen magnum at the
back and sides of the skull and passes forwards through the

27. middle ears and roof of the nose due to which skull is
sepearted from the spine.They are rare and occur after falls
from a height into feets or buttocks. This drives the vertebral
column into the skull.
7. Perforating fractures: These are caused by fire arms or
pointedsharp weapons like dagger or knives or axe.The
weapon pass through both tables of the skull leaving more or
less clean cut opening.
8. Diastic or sutural fractures : Seperation of the suture occur
in young person due to a blow on the head with blunt
instrument.
FIRE ARM INJURY

They are usually recognized without difficulty. The injuries
produced by fire arms vary depending on the projectile, the
muzzle velocity, distance, angle of firing and part of the body
involved.
The type of wound produced by a firearm depends on several
factors including:
a) Nature of the weapon
b) Composition of the missile
c) Range
d) Tissues traversed by the missile
e) Direction of fire

28. The Weapon
Ballistics is the study of firearms and ammunition. It is a very
highly specialized and complex science and cannot be fully
discussed here, but certain basic principles can be
considered.
There are two main types of guns:
 Those firing single missiles, e.g. rifles and pistols
 Those firing a mass of small missiles (shot) - shotguns.

Rifles and pistols are rifled weapons i.e. there is rifling (spiral
grooving) of the inside of the barrel which imparts spin to the
bullet, ensuring a stable flight by the gyroscopic effect
produced.

The long-barrelled weapons (rifles) have a high muzzle
velocity and are accurate over a long range (2,000-3,000
yards on average).

The short-barrelled weapons (pistols) have a low muzzle
velocity and are accurate over a relatively short range (400-
600 yards on average).

Pistols may be revolvers or automatics (semi-automatics).
Revolvers fire bullets from chambers in a revolving metal
cylinder. After the bullet is fired, the cartridge case remains

29. in the cylinder and must be removed by hand. The
“automatic” is a self-loading weapon, and the ammunition is
stored in a magazine in the handle of the gun and is fed into
the barrel of the gun as each bullet is fired. After the bullet is
fired the empty cartridge case is automatically ejected from
the gun.

The calibre of these guns is expressed as the internal
diameter of the barrel e.g. .38 inch, .45 inch or 9mm. The
basic unit of ammunition is the cartridge (or round), made up
of the cartridge case, the primer, the powder and the bullet.
Bullets are made of hard solid metal and fit into a cartridge
case (usually brass) that contains the powder, which
explodes when the firing pin on the hammer of the gun hits
the cartridge case and ignites the primer, forcing the bullet
from the gun. Hollowing out the tip of the bullet (hollow-
points; dum-dums) causes the bullet to shatter or deform on
contact causing greater damage.


Shotguns have a smooth bore i.e. the inside of the barrel is
smooth. The gun fires a cartridge composed of a mass of lead
pellets which fan out after being fired. The effect at close
range is that of one solid missile, but at a distance it is that of
several individual pellets. A bullet fired from a rifled gun
bears scoring (scratches) imparted by the inside of the
barrel. This scoring is characteristic of the weapon, providing

30. a "fingerprint" which can be used to identify the weapon
from which a bullet was fired.

It is therefore important that bullets recovered at autopsy
should NEVER be handled directly by metal forceps or other
hard instruments which might alter the scoring pattern.

Such bullets should be wrapped in protective wadding for
transportation to the forensic laboratory. Note that the
cartridge case bears marks produced by the firing mechanism
from which it is possible to identify the gun that was used. It
should also be treated with great care.
Bullet Wounds

Entry Wounds
The features vary depending on the range from which the
weapon is fired—contact, close (intermediate) range or
longer (indeterminate) range.

A gunshot wound is a controlled explosion and the bullet is
accompanied from the gun by a jet of flame, a cloud of gas,
burning and unburnt grains of gunpowder and soot from
burnt gunpowder. Entry wounds may show the stigmata of
the explosion to a lesser or greater extent.

31. (A) Contact wound
The muzzle is pressed against the skin. The heat of the
discharge causes scorching or charring of the wound. The
gases produced by the explosion of the cartridge enter,
stretch and split the skin producing a stellate or cruciform
tear. The tissue at the margin of the wound may contain soot
and powder.

(B) Close range (Intermediate range)
The wound is inflicted at less than arm's length i.e. < 2 - 3
feet. The particles of partly burnt or unburnt powder from
the muzzle are driven into the skin around the entrance
wound giving a stippled appearance called "powder
tattooing" or "powder burns". The area may be blackened
by soot. Soot may be wiped off the skin, but powder
tattooing cannot be wiped off. The bullet hole may be round
or split, the latter being relatively common when there is
underlying bone.

(C) Longer (Indeterminate) `range
The range is > 2 - 3 feet. The gun is too far from the skin for
the products of the explosion to have any effect. Therefore
the appearance of the wound is due entirely to the bullet.
The wound is usually round (but may be split by "tail-wag" if
the gun is fired from the extreme of its effective range
causing the bullet to lose its gyroscopic spin and start to
tumble).

32. Marginal abrasion/Abrasion collar/Abrasion ring
The margin of the entry wound in some close range and
longer range injuries may be abraded (“marginal abrasion”,
“abrasion collar” or “abrasion ring”) as the bullet inverts the
skin and abrades the epidermis as it enters. The shape of this
abrasion may help in determining trajectory.

Grease ring
The inner edge of the abrasion collar may be black due to
grease or lubricating oil and metal particles from the bullet.
Exit wounds
These show none of the stigmata of the explosion or soiling
seen in the entry wound. An exit would may be the same size
as the entry wound, but may be smaller or larger depending
on the range, type of weapon, type of bullet, the tissues
being traversed by the bullet, etc.

In a contact shot the entry wound is split by the explosive
gases and is therefore usually larger than its corresponding
exit wound. However, if the bullet comes out carrying bone
e.g. a shot to the skull, the exit wound may be larger than
the entry.

33. In a distant shot the exit wound may be the same size or
slightly smaller than the entry. In general, exit wounds tend
to be split with irregular, everted edges. As a rule, exit
wounds DO NOT show an abrasion collar, but exceptionally,
this may occur if the skin was pushed up against a hard
surface, e.g. concrete wall or floor at the time the bullet
exited. This is known as a shored exit wound.
CONCLUSION
Forensic expert determine the direction of impact, the type
of object that caused it and how often the contact was made,
often they're made by blows from a hammer or axe head.
Bite marks are also a form of crushing wounds. With a knife
or incised wounds the crime scene investigator must make a
distinction between cut and stab or puncture wounds and
among different types of piercing implements such as an ice
pick or small knife. Most knives have a flat edge and a sharp
edge which can be seen in the wound angels. Some wounds
are defensive such as cuts made on the palms or fingers of a
victim's hands. Some time cuts are associated with suicidal
gestures are known as hesitation wounds as the person
attempts to inflict self-damage. As with all instances of a
firearms offence that results in an injury, measurements are
taken along with photographs to aid in the identification of
the weapon used, it is necessary for a Forensic expert.
Powder residue samples are taken and if the victim dies as a
result of their gunshot wound, the round is removed for
ballistic analysis from the corpse at the autopsy stage. The
forensic scientists and investigating officer scour the crime

34. scene looking not only for the weapon involved as they are
sometimes disposed of but also for spent shell casings and/or
loose rounds that were fired but did not hit their intended
targets and imbedded themselves in nearby walls, doors or
the ground.
REFERENCES
1. Olshaker et al. Forensic Emergency
Medicine. Lippincott Williams & Wilkins:
2001
[2] Knight B. Forensic Pathology. 2nd ed.
London: Amold, 1996; pp.232.
[3] Polson CJ, Gee DJ and Knight B. The
Essentials of Forensic Medicine. 4th ed.
Oxford: Pergamon Press, 1985; pp.125-127.
[4] Sharma GK, Sarangi MP, Tyagi AK, Kumar
B. Medico-legal Interpretation of Stabbing
and Cutting Injuries (An Autopsy Study).
JFMT, 1994; 11(1&2): 21; also Crowley,
Sharon R. Sexual Assault: The MedicalLegal
Examination. McGraw-Hill/Appleton &
Lange: 1999.
[5 ] Scolan V, Telmon M, Blanc JP, Allery D,

35. Charlet RD. Homicide - Suicide By Stabbing
Study Over 10 Years In The Toulouse
Region. The American Journal of Forensic
Medicine & Pathology, 2004; 25(1):33-36.
6. TEXTBOOK OF FORENSIC MEDICINE AND TOXICOLOGY:
V. V. PILLAY
7. www.forensicindia.com
8.