Mechanical injuries caused by sharp cutting weapons like knives can be classified as incised wounds, chop wounds, or stab wounds based on the action used. Incised wounds are caused when an object is drawn across the skin, producing a clean cut. Chop wounds result from a heavy blunt force weapon and are typically deep and gaping. Stab wounds occur when a narrow pointed object is thrust into the body, leaving a small, puncture-like entry wound. The shape, size, depth, and direction of the wound can provide clues to the weapon used and the events that caused the injury. Careful examination of wounds and potential weapons is important for medicolegal investigations.

1. Mechanical
injuries
Injuries caused by sharp cutting weapons

2. This is what we will see
1. Classification of injuries
2. Injuries caused by sharp
cutting objects

3. Injuries are classified in 3 ways
• Simple
• Grievious
• Mechanical injuries
• Due to blunt force
• Abrasions
• Contusions
• Lacerations
• Fractures
• Due to sharp
force
• Incised
• Chop
• Stab
• Firearms
• Firearm
injury
• Blast injury
• Thermal injuries
• Due to cold
• Frost bite
• Trench foot
• Immersion
foot
• Due to heat
• Burns
• Scalds
• Chemical injuries
• Corrosive acids
• Corrosive alkalis
• Physical
• Electricity
• Lightening
• X-rays
• Radioactive subs.
• Explosions
• Suicide
• Homicide
• Accident
• Fabricated
• Self-inflicted
• Defence

4. Our interest is in
• Injuries due to sharp cutting weapons
• Incised wounds
• Chop wounds
• Stab wounds

5. Incised wounds
• Causes
• Characters
• Age
• Histopathology
• Medicolegal importance
• Special topic- Wounds by glass

6. Causes
• Striking the body with edge of the sharp cutting weapon
• By drawing the weapon
• By using a weapon like saw where multiple cuts merge
into one

7. Characters
• Margins:
• Clean- cut, well-defined and everted (may be inverted if
muscle fibres adhere to skin as in scrotum)
• no abrasion or contusion (present if weapon has irregular
edge or nicked edge)

8. Characters
• Width
• Greater than edge of weapon
(due to retraction of divided
tissues and shaking of blade)

9. Characters
• Length
• Length > Width
• Length > Depth
• Length is not related to
cutting edge of weapon (as
it may be drawn to any
distance)
depth
width

10. Characters
• Shape
• Usually Spindle shaped
• Zig-zag if skin is loose as in
axilla
• Crescentic if present on convex
parts like buttocks

11. Characters
• Hemorrhage
• More due to cleanly cut vessels
• Spurting of artery when cut is
characteristic

12. Characters
• Direction
• Deeper at beginning
(head of wound)
• Shallow at end
(tailing of wound)
• Above features help to know
the direction of wound
Tailing

13. Characters
• Beveling cut
• If blade enters obliquely
• Tissue visible at one margin
and other margin is beveled
(overhanging or undermined)

14. Age of incised wound
Fresh:
Hematoma
formation
12 hours:
Edges are red,
swollen and
adherent with
blood and
lymph;
leucocytic
infiltration
24 hours :
A continuous
layer of
endothelial
cells covers
the surface;
overlying this
a crust or
scab of dried
clot is seen

15. Histopathology
Few minutes: Dilatation
of capillaries and
margination and
emigration of
neutrophils
Within few hours;
monocytes’ appear in
the exudate.
12 hours: Reactive
changes occur in the
fibrioblasts at the site of
injury
15 hours: Monocytes
begin to undergo mitotic
division.
24 hours: Epithelium
begins to grow at the
edges. Vascular buds
begin to form.
72 hours: Vascularised
granulation tissue is
formed.
4 to 5 days: New fibrils
are formed.
One week: Scar
formation in small
incised wound.

16. Medicolegal importance
They indicate the nature of weapon (sharp-edged)
The age of the injury can be determined
They give an idea about the direction of the force
Position and character may indicate mode of production, i.e.,
suicide, accident, homicide
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17. Wounds by Glass
• Wounds are lacerated, but can
resemble incised and stabs
• If a sharp-pointed piece of glass
enters by its point, it has a stab-like
appearance
• Margins show tiny side cuts (due to
irregularities of the glass)
• Particles of glass may be found in it
• Assault with broken glass shows
multiple irregular incised-type
wounds of variable depth
SPECIAL TOPIC

18. Chop wounds
• Causes
• Characters
• Features
• Medicolegal importance

19. Causes
• Violent blow with
the sharp-cutting
edge of a fairly
heavy weapon, like
a hatchet, an axe,
sword, broad heavy
knife, or meat
cleaver

20. Characters
• Margins
• Sharp
• May show slight abrasion
• Ragged and bruised (if
edge is blunt)
• Marked destruction of
underlying organs

21. Characters
• Dimensions
• They are deep gaping
ones.
• The dimensions of wound
correspond to cross
section of penetrating
blade.

22. Characters
• Direction
• Usually the lower end (heel) of the axe strikes the surface
first, which produces a deeper incised wound than the
upper (toe) end
• The deeper end indicates the position of the assailant
• In the skull, the undermined edge of the fracture defect is
the direction in which the force is exerted, and the slanted
one is the side from which the force was directed
• In case of long bones, the bone fragments get loosened on
the opposite side of the force.

23. Features
• Undermining in the direction
towards which the chop is
made
• When the whole blade strikes
the body at the same time, the
depth may be same
throughout it

24. Features
• If the extremities are attacked,
there may be complete or
incomplete amputation of
the fingers or other bones, and
the joints may be separated or
dis-articulated.

25. Features
• if the weapon strikes
obliquely, a piece of the skull
may be removed.
• If the chopping blow is
tangential, a disk- shaped
portion of bone or skin or soft
tissue may be cut away.
• The neck may be almost
completely separated.

26. Medicolegal importance
Most of these injuries are homicidal and usually inflicted on the exposed
portions of the body like the head, face, neck, shoulders and extremities.
Accidental injuries are caused by power fans, band saws or ship or
airplane propellers, which may lacerate the soft tissues extensively or
amputate parts of the body.
Suicidal chop injuries are very rare.
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27. Stab wounds
• Causes
• Characters
• Complications
• Examination of wound
• Examination of weapon
• Medicolegal importance
• Special topic- Concealed puncture
wound & Incised stab wound

28. Causes
• When force is delivered along
the long axis of a narrow or
pointed object, such as knife,
dagger, nail, needle, spear,
arrow, screw driver, etc. into
the depths of the body.
• Driving the object into the
body, or from the body’s
pressing or falling against the
object

29. Characters
• Margins
• Edges are clean-cut.
• No abrasion or bruising (in full
penetration of the blade, abrasion and
bruising (hilt mark) may be produced)
• Abraded and ragged if the cutting
edge is blunt.
• Mark will be
• symmetrical, if the knife strikes at right
angle
• prominent above the stab wound, if the
knife strikes in a downward angle
• abrasion below the stab wound, if the
knife strikes in an upward angle
• In oblique types, a knife striking from
the right will have an abrasion on the
right side and vice versa.

30. Characters
• Length
• Slightly less than the width of the
weapon upto which it is driven in
(because of stretching of the skin)
• For measuring the length of stab
wound, the edges should be
brought together.
• Deliberate lateral, forward, or
backward movement of the weapon
during its withdrawal from the
body tends to widen the wound,
and the length will be more than
the maximum width of the blade
• If the instrument is thrust in, and is
then completely withdrawn with
the cutting edge dragging against
one end, it would be extended
superficially, producing a tail.

31. Characters
• Width
• The maximum possible width of
the knife blade can be
approximately determined if the
edges of a gaping wound are
brought together
• Elasticity or laxness of the skin
can change the width by one to
two millimeters.
• A stab wound inflicted when the
skin is stretched will be long and
thin, which becomes shorter and
broader when the skin is relaxed
• The opening may be enlarged by
backward, forward or a lateral
movement of the weapon.

32. Characters
• Depth
• The depth (length of track) > width and length of
the external injury
• It depends on
• Condition of the knife:
• The resistance offered by the tissues or organs
• Clothing
• Stretched skin is easier to penetrate than lax skin, e.g. chest
wall.
• If knife strikes the skin at right angle, it usually penetrates
more deeply than when it strikes from some acute angle.
• When the knife penetrates the skin rapidly, e.g. if the body
falls or runs on to the blade, the momentum of the forward
moving body is sufficient to cause fatal injury

33. Characters
Shape
Dependent on
Type of implement
Cutting surface
Sharpness
Width and shape of the weapon,
Direction of thrust
Movement of the blade,
Cleavage direction
Movement of the person stabbed
Tension or relaxation of the skin.

34. Characters- Shape
• If a single-edged weapon is
used
• the surface wound will be
triangular or wedge- shaped, and
one angle will be sharp, the other
rounded, blunt or squared off.
• Blunt end of the wound may
have small splits (often in two
places) in the skin, so-called
“fishtailing”, if the back edge of
the blade is stout

35. Characters- Shape
• Double-edged weapon produces
• elliptical or slit-like and both angles
will be sharp, or pointed
• Round object like the spear
produces
• circular stab wound.
• Round blunt-pointed object, such as
a pointed stick, or metal rod
produces
• Circular surface wound with
inverted ragged and bruised edges.
• The blunter the tip of the object, the
coarser or more stellate will be the
hole it makes.

36. Characters- Shape
• Pointed square weapon produces
• Cross- shaped injury, each of the 4
edges tearing its way through the
tissues
• Stabbing with a fork produces
• Clusters of 2 or 3 wounds depending
upon the number of prongs on the
fork.
• Screwdriver produces
• Slit-like stab with squared ends
(rectangular) and abraded margins.

37. Characters- Shape
• Ice-picks produce
• Wounds resembling small
caliber bullet wounds.
• Knife with a serrated back
edge produces
• Stab wound, the back edge of
which may be torn or ragged.
If the knife enters obliquely,
serrated abrasions may be
seen on the skin adjacent to
the end.

38. Characters
• Direction
• In solid organs, the principal direction should be noted first
and other next, e.g., backwards and to the right. If the
weapon is partially withdrawn and thrust again in a new
direction, two or more punctures are seen in the soft parts
with only one external wound.
• If it is perforating, it should be described in sequential
order:
• stab wound of the entrance
• path of the track, and its exit
• If it is penetrating, the wound of entrance should be
described first, then the depth and direction of wound track.

39. Complications
• Marked internal hemorrhage or injuries to internal organs.
• Wound may get infected due to the foreign material carried
into it.
• Air embolism may occur in a stab wound on the neck which
penetrates jugular veins. Air is sucked into the vessels due to
the negative pressure.
• Pneumothorax.
• Asphyxia due to inhalation of blood.

40. Examination of wound
• The following points should be noted :
• 1) Identification and labeling of cuts and damage to clothing.
• 2) Distribution of blood stains.
• 3) Removal of clothing, layer by layer.
• 4) Identification and labeling of wounds.
• 5) Wounds:
• Position (height from heels),
• location (measurements from fixed anatomical landmarks),
• description including margins, size, shape, ends, extension,
• direction,
• depth,
• trauma to viscera,
• estimation of force required,
• foreign bodies.

41. Examination of weapon
• The doctor should note :
• Length, width and thickness of the blade,
• Whether single-edged or double- edged,
• Degree of taper from tip to hilt,
• Nature of the back edge in a single-edged weapon, e.g.
squared-off, serrated, etc.,
• Face of the hilt guard adjacent to the blade,
• any grooving, serration or forking of the blade, and
• Sharpness of the extreme tip of the blade and the cutting
edge.

42. Medicoloegal importance
Shape of the stab wound indicates class and type of weapon which may have caused the
injury.
Depth of the wound will indicate the force of penetration.
Direction and dimensions indicate relative positions of the assailant and the
victim.
Age of the injury can be determined.
Position, number and direction of stab wound may indicate manner of production,
i.e., suicide, accident, or homicide.
If a broken fragment of weapon is found, it will identify the weapon or will connect an
accused person with the crime.
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43. Concealed Puncture wounds
• These are puncture wounds caused on concealed parts of
the body, such as nostrils, fontanella, fornix of the upper
eyelids, axilla, vagina, rectum, and nape of the neck
• Fatal penetrating injuries can be caused without leaving
any readily visible external marks, e.g., thrusting a
needle or pin into the brain through the fontanels, through
the inner canthus of the eye, or into the medulla through the
nape of the neck
• These injuries may not be detected unless searched
carefully.
SPECIAL TOPIC

44. Incised-stab wound
• Starts as an incised wound and ends as a stab wound by the sudden
thrust of the blade into the body, or starts as a stab and becomes incised
as the knife is pulled out of the body at a shallow angle to the skin surface
producing an incised.
• If a nick or a pork-shaped cut is present at the end opposite to the
incised portion, then the wound has started as an incised and ended as a
stab. If the fork is at the end of it where the incised arises, then the wound
has started as a stab.
• The external and internal appearances help to give an opinion upon:
• dimensions of the weapon,
• type of weapon,
• taper of the blade,
• movement of the knife in the wound,
• depth of it,
• direction of the stab, and
• amount of force used
SPECIAL TOPIC

45. All the text is strictly taken from
The essentials of forensic medicine
and toxicology 31st edition –
Dr.K.S. Narayan Reddy
All images are from google images
or created in powerpoint itself and
edited using paint