Forensic Medicine

1. MECHANICAL INJURIES
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2. MECHANICAL INJURIES
 Definition: Injuries caused by application of physical
violence to the body are known as Mechanical
injuries.
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3. Classification of Mechanical Injuries
Blunt Force Injuries/Trauma:
Abrasions.
Bruises(Contusions)
Lacerations.
Sharp Force Injuries/Trauma:
Incised wounds.
Stab wounds.
Chop wounds.
Fractures.
Fire arm injuries.
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4. MANNER OF CAUSATION
 Self – Inflicted (suicidal)
 Assaults by others (Homicidal)
 Accidental
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5. ABRASION
DEFINITION:
 1. It is a superficial injury involving
only the superficial layers of skin.
(epidermis).
 2. The outer layers of skin are
scratched or removed leaving a
bare area with little or no bleeding.
 3. These heal rapidly in few days
and leave no scar.
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6. MECHANISM OF CAUSATION
CAUSED BY
a) RUBBING.
b) SCRAPING.
CAUSATIVE AGENTS.
SHARP OBJECTS= FINGER NAILS, PIN,
THORN SHARP POINTED OBJECTS.
ROUGH SURFACE= GROUND, ROAD, FLOOR.
BLUNT OBJECTS= KICK WITH BOOT, ROPES,
STICKS, WHIP, TEETH.
OF SKIN WITH AN OBJECT
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7. CLASSIFICATION OF ABRASIONS
 1. Scratches.
 2. Grazes. Moving abrasion.
 3. Imprint abrasion.
 4. Friction abrasion.
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8. CLASSIFICATION:
a) SCRATCHES:
 It is a linear injury caused by a
sharp pointed object such as pin or
finger nail running across the skin.
 CHARACTERISTICS:
 The direction of scratch is indicated
by sharp edge initially and heaped up
epithelium/ epidermis at the end.
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10. CLASSIFICATION OF ABRASION
 b) GRAZES / SLIDING/
FRICTIONAL BURNS / GRAVEL
RASH :-
 It is produced when broad surface
of skin slides against a rough
surface.
 like ground, road also called as
brush burns.
Example seen in:
o Road traffic accidents
(RTA).
o Dragging of body on a
ground.
o Glancing kick with a boot
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11. MEDICO-LEGAL SIGNIFICANCE:
 Direction of force: shown by situation of “tags”.
 Identification of scene of incidence: presence of
foreign body (dirt or grit) in the graze. Compared with
the scene.
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12.  c) FRICTION ABRASION: Are
caused by rubbing the skin surface
with cords or ropes.
 Example:
 Ligature marks in cases of hanging,
strangulation.
 Blows with lash.
 Friction between skin & edges of
garments.
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13. CLASSIFICATION OF ABRASION
 d) IMPRINT/ STAMPED/
PRESSURE/
CONTACT/PATTERNED/
CRUSHED ABRASION:
 It is produced as a result of direct
impact or pressure without relative
movement.
 Example:
 Tire mark.
 teeth marks.
 ligature pattern.
 muzzle imprint. 13

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15. MEDICO-LEGAL SIGNIFICANCE:
Identification of offending object.
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16. MEDICOLEGAL ASPECTS
 It provides valuable information about
 1. Site of impact and possibility of internal injury 
These indicate that some force has been applied to the
body.
 2. Identification of Object causing injury
 For example as in case of Patterned or imprint abrasions,
Ligature in hanging, tire marks in RTA.
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17. MEDICOLEGAL ASPECTS
 3. Cause of injury
 The site of abrasion helps to determine cause of
injury, For example;
 On Neck in Throttling.
 On Nose and mouth in smothering
 On thighs and genitalia in sexual assault.
 4. Direction of Injury
 Sharp margins initial and heaped up epithelium on it,
terminate serrated borders initially and heaped up
epithelium at the end.
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18. DATING AN ABRASION (AGE)
OBSERVATION TIME
BRIGHT RED FRESH
RED SCAB
DRIED
BLOOD/SERUM
12-24 HOURS.
REDDISH BROWN
SCAB
2-3 DAYS.
HEALING FROM
PERIPHERY
4-7 DAYS.
COMPLETE
HEALING
10-14 DAYS. 18

19. DIFFERENCE B / W ANTE MORTEM & POST
MORTEM ABRASIONS.
INDICATOR A.M. P.M.
1. COLOR BROWNISH ON
DRYING
YELLOW ON
DRYING
2. MARGINS. BLURRED (DUE TO
VASOCONSTRICTIO
N)
SHARP
3. VITAL
REACTION
PRESENT ABSENT
4. SIGNS OF
REPAIR
PRESENT ABSENT
5. BLEEDING PRESENT ABSENT
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20. BRUISE (CONTUSION)
DEFINITION:
 It is a hemorrhage into the tissues, due to
rupture of vessels by the application of blunt
force, without breach of covering tissue (skin or
capsule).
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21. DIAGNOSTIC FEATURES:
= Shape may correspond the shape of causative object.
= Reddened area when fresh.
= Pain.
= Swelling.
= Size varies from pinhead to an extensive haematoma.
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22. CAUSES:
1. SPONTANEOUS (DUE TO DISEASE): Disease of
blood, vessels, scurvy, leukaemia.
2. TRAUMATIC:
Blows with club, fist, kicks, stone & bricks.
Firm griping of weak persons, RTA.
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23. CLASSIFICATION OF BRUISE
 DEPENDING UPON DEPTH OF THE TISSUE
INVOLVED:
 Intra dermal bruise.
 Subcutaneous bruise.
 Deep/delayed bruise /visceral bruise.
DEEP BRUISE MAY BECOME EVIDENT AFTER SOME
TIME (2-3 DAYS).
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24. ECTOPIC BRUISE:
 A bruise may not be present necessarily at the site of
impact.
 The extravasated blood may move along tissue planes
under gravity influence and gets collected at a distant place
(gravity shifting).
 EXAMPLE:
- BLOW ON FOREHEAD OR FALL ON VERTEX 
BLACK EYE.
- FACTURE HEAD OF FEMUR  LATERAL ASPECT OF
LOWER THIGH.
- BLOW ON OUTER PART OF THIGH  BRUISE AROUND
KNEE.
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25. SPECTACLE HEMATOMA, BLACK EYE OR
PERIORBITAL HEMATOMA OR RACCOON SIGN.
 A bruise round the tissues of the eyes & eyelids
may result called as Spectacle Hematoma,
 It occurs due to
 A blow to the orbit
 Fractured orbital roof
 A blow to the forehead
 A fall on the vertex.
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27. BATTLE’S SIGN
 A bruise behind the ear called Battle’s Sign
may result from fall on the vertex or fracture
of the base of the skull rather than a direct
blow behind the ear.
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28. FACTORS MODIFYING APPEARANCE OF BRUISE
 Site of Injury
 Vascularity of area
 Age
 Sex
 Color of skin
 Nature of disease
 Gravity shifting of blood
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29. 1. SITE OF INJURY
 IMPORTANT SITES
1 Areas covering bones
2 Loose tissue
 Bruising more marked in area covering the bones
without any intervening fibrous tissue e.g. over tibia.
 No bony support for abdominal walls.
 Bruising is rare after physical impacts on abdomen.
 Absence of bruising is no proof of undamaged
underlying tissue/viscera
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30.  Bruising appears easily around lax tissue of eyes, face,
genitals e.g. Black eye – with a small blow.
 Bruise formation on scalp is uncommon except in birth
trauma in a new born.
 Rare bruising on palm/soles
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31. 3) AGE:
Children (due to loosening of skin) & old (due to loss of flesh
& changes in blood vessels) bruise easily.
4) SEX: Females (obese) bruise easily.
5) VASCULARITY OF PART: Bruising is directly proportional
to vascularity of affected part.
6) COMPLEXION: Visibility better and clear in fair skinned
people.
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32. 7) PRESENCE OF DISEASE.
 Coagulation factor deficiency.
 Disease of blood vessels.
 Diminished platelets (thrombocytopenia).
 Persons with nutritional deficiency.
 Blood disorders (leukemia)
 Arteriosclerosis
 Varicose veins.
 Obese
 Alcoholics
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33. MEDICO-LEGAL SIGNIFICANCE
 Indicates offending object (blunt).
 Gives idea about degree of violence.
 Time of injury.
 Motive/purpose of injury.
 In throttling, pressure of pads of finger  homicide.
 Bruise on back of fingers, hand & forearms
( Defensive act).
 Multiple small bruise on arms just below shoulders
 (Force full grasping during struggle)
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34. MEDICO-LEGAL SIGNIFICANCE
 Adults: alcoholics, drug dependent.
 In children: battered baby syndrome.
 Tram track bruise: results from blow with rod, stick
or whip & any flexible object. (Torture). Central
depressed pale area with margins showing blood &
swelling.
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36. MEDICO-LEGAL SIGNIFICANCE
 Suction petechie: bruising on the
cheeks & breast. (Sexual
intercourse),(love bites)
 Bruise on the medical aspect of
thigh, vulva & around anus indicate
forceful sexual intercourse.
 Bruising of cervix shows dilatation
cervix.
 Bruising of buttocks indicate torture
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37. MEDICO-LEGAL SIGNIFICANCE
 Due to sudden compression of subcutaneous tissues,
fat may be displaced and enters into injured vessels
lead into fat embolism.
 Accidental: common occurrence.
 Suicidal: not common.
 Homicidal: common
 Self inflicted: artificial bruised area produced by
rubbing marking nut juice or Calotropis, or root of
plumbago over skin.
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38. DIFFERENTIATE BETWEEN ARTIFICIAL BRUISE &
TRUE BRUISE
Findings Artificial Bruise True Bruise
Cause Juice of Plant Blunt force
Situation On accessible parts Any part
Colour Dark brown Changes of colour
Margins Well defined Less defined
Shape Irregular Shape of weapon
Swelling, Redness, & echymosis Not present Present with slight swelling
Contents Serum Blood
Itching Present Absent
Chemical Tests Positive Negative
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39. DATING A BRUISE (AGE OF BRUISE)
DONE BY:
- Macroscopic examination (color changes).
- Microscopic examination (blood pigments).
Mechanism:
Blood, due to disintegration of RBC by haemolysis, releases
haemoglobin that breaks down into haemosidrin,
haemotoidin & bilirubin by the action of histiocytes & tissue
enzymes.
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40. DATING A BRUISE (AGE OF BRUISE)
CHANGES ARE SEEN FROM PERIPHERY TO CENTER.
COLOUR TIME OF INJURY PIGMENT
Fresh (Red) Fresh Hemoglobin
Red to blue One day Deoxygenated Hemoglobin
Bluish black to brown 2-4 Days Hemosiderin
Green 5-7 Days Haemotidin
Yellow 7-10 Days Billirubbin
Completely disappears 14 Days/ 2weeks Normal
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41. MICROSCOPIC CHANGES:
Hemosidirin within macrophages:
not less than 24-48 hours.
Hemotoidin within Macrophages: not less than 3 days.
Bilirubin extra cellular: not less than 7 days.
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