Mechanical Injuries

1. MECHANICAL INJURIES
Dr. JINESH P. S.
10/08/2011
Dr Anamica Chakraborty
Senior Resident
Dept. Of Forensic Medicine

2. CONTENTS :
INTRODUCTION
CLASSIFICATION OF INJURIES
MECHANISM OF INJURIES
ABRASION, BRUISE,LACERATION
& Its SIGNIFICANCE

3. INJURY :
Section 44 IPC ?????.........
ASSAULT : THE UNLAWFUL PLACING OF AN INDIVIDUAL IN
APPREHENSION OF IMMEDIATE BODILY HARM WITHOUT HIS / HER CONSENT
HURT:

4. CLASSIFICATION OF INJURIES
•Mechanical
injuries
•Thermal injuries
•Chemical injuries
On the
basis of its
causation :

5. Mechanical injuries
By hard blunt weapon –
Abrasion
Bruise
Lacerated injuries
Fracture of bone or dislocation of
joint

6. By sharp cutting weapon –
Incised injuries, Chop wound
By pointed tip weapon -
Stab injuries –
Punctured
Penetrating
Perforating
By firearms – Shotguns, Rifled

7. 2. Thermal injuries-
 Due to cold – a) Hypothermia b) Frost bite
c)Trench foot d) Immersion foot
Due to Heat –
General effects ----
a) Heat hyperpyrexia
b) Heat exhaustion
c) Heat cramp
Local effects---- a) Burn b) Scald

8. 3. Chemical injuries -
 Corrosive acids
 Corrosive alkalies
4. Physical agents –
 Electricity
Lightning
X-ray, UV Rays
Radiations

9. Medico-legal classification -
Suicidal Homicidal
Accidental
Defense
wound

10. On the basis of time of inflection -
Antemortem Postmortem

11. On the basis of severity/ Legal
Hurt
Grievous
hurt

12. Mechanism :
Properties of
injuring force
Velocity
Mass
Shape
Peculiarities of
area affected
Elasticity
Toughness

14. ABRASION :
Form of mechanical injury
involving destruction of
epidermal layers of the skin
and dermal papillae .

17. TYPES :
Scratch
Graze
Pressure
Impact/ Imprint

18. SCRATCHES
EXAMPLE
By fingernails (throttling)
By thorns
By tip of knife

19. SCRATCHES
OVER
NECK

20. GRAZE
ABRASION
Show multiple linear
furrows.
BRUSH BURN
(FRICTION BURN)

21. GRAZE ABRASION

23. PRESSURE
ABRASION :
By crushing of
epithelium due to
pressure & friction

24. IMPRINT
ABRASION :
Eg. –
Radiator grill impression on skin of victim of RTA, Beating by a
chain
Tire marks in run over accidents
Muzzle impression

25. PATTERNED ABRASION

26. SEAT BELT INJURY

28. AGE OF
ABRASION

29. Time Colour Cause
Fresh abrasion
<12 hrs
Bright red non scab Oozing capillary blood
12-24 hrs Bright red scab Dried up lymph & blood
2 to 3 days Reddish brown scab
4 to 7 days
>7 days
Dark brown scab,
Epithelisation starts
Scab dries, shrinks and falls off
leaving depigmented skin
Peripheral healing with
shrinkage of scab
New epithelium
formation

30. POSTMORTEM ABRASIONS :
Lack vital reaction
Dark & leathery
Scab formation absent
Dermis will be pale
Site – usually on bony prominence, Ant erosion on external orifices
Ants may invade small blood vessels & blood may seep – D/D of
abrasion

31. P M ANT BITE MARKS

32. MEDICOLEGAL SIGNIFICANCE

33. Indicate site of contact with an object and direction of
application of force.
May be only external indication of a deep seated injury
Patterned abrasion – relationship of wound with object which
produced it.
Stage of healing help in determining time of occurrence – only
approximate
Dirt, dust, grease, sand around abrasion connects scene of
crime

34. MEDICOLEGAL SIGNIFICANCE (Continued…..)
Distribution give valid information about nature of crime
Possibility of skin fragments of assailant may retained under the
nail.
Around nose & mouth – smothering
Around breast & genitalia – sexual assault
Crescentic abrasion on neck – throttling
On face of assailant – struggle

35. CONTUSION or BRUISE

36. CONTUSION or BRUISE
A bruise is an effusion of blood
into the tissues underneath the
skin due to rupture of blood
vessels as a result of application
of blunt force or violence.

38. •Petechiae
•Ecchymosis
•Bruise
•Hematoma

39. Factors affecting the formation of bruise
 Nature and severity of the force
 Vascularity of the affected area
 Number and size of the blood vessels
involved
 Condition and size of the blood vessels
involved

40. Predisposing factors :
Sex –
Age –
Colour of the skin –
Diseases –
Chronic alcoholics – Easily bruises – Cutaneous
vasodilatation

42. AGE OF CONTUSION
Time Colour Cause
Fresh / few hours Red Oxy-Hb
Few hours -3 days
Blue Deoxy-Hb
4 day Brown Haemosiderin
5- 6 days Greenish Haematoidin
7 – 12 days Yellow Bilirubin
2 wks Normal
Pig. removed by
phagocytosis

47. PATTERNED BRUISING
• Eg. -
 Contact fire arm injury
Motor car
Stomping
Blow by hammer or rod
Kicking

48. SLAP MARK - CHEEK

49. TRAM LINE CONTUSION
Objects like belt
Two parallel linear contusions
separated by a relatively pale,
undamaged section of skin

50. BITE MARK :

53. ARTIFICIAL BRUISE
By applying juice of irritant plant like
Calotropis, Marking nut (Semecarpus anacardium), Lal Chitra
(Plumbago rosea)

54. DIFFERENCES
TRUE BRUISE FALSE BRUISE
Colour Changes with time Dark brown
Margin
Location
Diffuse, irregular
Anywhere
Well defined, Covered with
vesicles
Accessible parts
Content Haematoma Serous fluid
Local reaction Signs of inflammation over
the bruise
Surrounding area
Vesicles Absent Present
Chemical test ( - )ve (+)ve for vesicant
Itching No Yes

55. PM Staining Bruise
Cause
Site
Collection of
blood
Incision
Colour
Effect of pressure
Microscopically

56. MEDICOLEGAL
SIGNIFICANCE

57. Nature of object used & force applied can be predicted
Color change help to deduce time of occurrence
Different colors on different parts of body is indicative
of chronic abuse – battered baby syndrome
If any doubt about ante-mortem/post-mortem –
histopathology – vital reaction if ante-mortem

58. MEDICOLEGAL SIGNIFICANCE
(CONTINUED….)
In manual strangulation – give indication of
method of attack & position of assailant
Bruising of thigh & genitalia – rape
Dirt, sand, grease – connect scene of crime
Contusion in & around nose & lips -
smothering

59. Which one is of greater value-
Abrasion or Bruise ?????

61. Lacerations are tears or split of skin, mucus
membrane, muscle or internal organ,
produced by application of blunt force to
the body, which stretches tissue beyond
their limits of elasticity.
Lacerated wound :

63. 1. Blow with hard blunt weapon
2. Fall from height on rough or
projected surface
3. By accidents – RTA
4. By fist blow or kick
5. Over stretching of the skin
Mode of production :

67. Characteristic of lacerated wound :
1. Margins –
2. Subcutaneous and deeper tissues –
3. Gaping –
4. Tissue bridges –
5. Less bleeding
6. Bruising -

68. 7. Hair bulbs crushed or torn
8. Not usually correlates with the shape
and size of weapon
9. Commonly infected
10. Mud, sand, glass, brick particles
inside the wound

69. TYPES –
1. Split
2. Stretch
3. Avulsion
4. Tear
5. Cut

74. Medicolegal aspects :
1. Always caused by blunt force injury
2. Homicidal , accidental or suicidal
3. Defence wound
4. AM and PM laceration