Mechanical injuries.pptx

Forensic Medicine

1. Dr Nikita Prabhakaran G Assistant professor

2. Medical definition Injury = Wound Any breach of natural continuity of skin or mucous membrane

3. Legal Definition - INJURY (44 IPC) Any harm Whatever illegally caused to any person In Body Mind Reputation Property

4. Classification of Injuries Based on causative factors 1. Mechanical / Physical Injury 2. Thermal Injury (Heat and cold) 3. Chemical Injury 4. Miscellaneous (Electrical, Radiation, Lightning, Blast)

5. Mechanical Injuries Caused by blunt force : 1. Abrasion 2. Bruise/ contusion 3. Lacerated wound 4. Fracture / dislocation Caused by sharp force 1. Incised wound 2. stab wounds Caused by firearms

6. ABRASION Characterised by denudation of superficial layers of skin (usually epidermis & papillary dermis) Caused due to friction against a rough surface And usually heals without a scar formation

7. Types of abrasion 1. Scratch/ linear sharp or pointed object surface layers are collected in front of the object clean area at the start heaped up epithelium at the end Eg : fingernail abrasions, thorn, pin

8. 2. Graze abrasion (sliding/grinding/scrape abrasion) Horizontal or tangential friction Between skin and hard rough surface Uneven longitudinal parallel lines Direction can be appreciated (heaping up of epithelium at the opposite end) Most common Particles of glass, gravel or dirt may be found

9. Brush burn wider area rubbing violently , turn firm on drying even without a scab Friction burn - wider excoriated area redness no linear marks when covered by clothing

10. 3. Pressure abrasion Direct impact or linear pressure of an object over skin (Perpendicular) Inward crushing of epithelium For longer periods Examples: Ligature mark Nappy rash Corneal abrasion – prolonged contact lens use

11. 4. Imprint abrasion When there is a considerable amount of force That acts perpendicularly But only for a short period of time Patterned abrasions (when the causing agent can be identified) Otherwise called a signature abrasion Eg : tyre tread marks

12. Age of abrasion Gross and histopathological changes Gross: (1) Fresh – Bright red (2) 1 day – Blood and lymph dries up. Bright red scab forms (3) 2-3 days – Reddish brown scab (4) 4-7 days – ( i ) Scab becomes dark brown (ii) Epithelium grows under the scab and covers defect. Scab becomes ready to fall (5) > 7days – Scab dries, shrinks and falls

13. Antemortem abrasions/ post-mortem abrasion Characteristic Antemortem abrasion Postmortem abrasion 1. Site anywhere on the body Only on bony prominences 2. Colour Bright reddish brown Yellow translucent parchment like 3.Exudation More. Scab slightly raised Less. Scab lies low 4. Microscopic Congestion, vital reactions No congestion /vital reaction

14. Medico Legal Importance of Abrasions (1) Direction of force – can be estimated from tissue tags (2) Force of impact – can be judged (3) Foreign matter sticking over abrasions – may give an idea of scene of crime [ eg grass, gravel, sand etc] (4) Imp and only sign – of internal injury sometimes

15. (5) Manner of production – ( i ) Generally accidental or homicidal in nature (except Ligature mark in hanging) (ii) self-inflicted – false abrasions (6) Nature – ( i ) Usually simple because they heal without scarring (ii) Do not pose danger to life ( unless multiple and massive, or involve underlying vital organs) ***Grievous abrasions  corneal abrasion, ligature mark tyre tread mark

16. (7) Time of assault – can be calculated (8) Type of offence – is indicated by site of abrasions ( i ) around anus - homosexuality (ii) around breast, cheeks, neck, inner side of thighs indicate sexual assault (iii) over face – indicate struggle (iv) over mouth and nose – in smothering (v) over neck – indicate throttling (9) Weapon – can be identified from patterned abrasions. Sometimes peculiarity of the offender’s nails can be estimated [ eg long, crooked, broken, irregular etc).

17. Differential diagnosis 1. Burns 2. Excoriations due to excreta (Nappy rash) 3. Pressure sore 4. Ant erosions 5. Drying up of skin after death

18. Contusion Mechanical injury caused by blunt force Characterised by extravasation of blood into the subcutaneous tissue Due to rupture of subcutaneous vessels

19. Salient features: (1) Situation – the dermis and subcutaneous tissues (some-times in the fat layer) (2) Color – Lighter in the center (extravasated blood is pushed outward) (3) Cause – by blunt force, (4) Associated findings – (a) painful, tender (b) crushing and tearing of s/c tissues (c) usually no destruction of skin (d) may occur in association with abrasions or lacerations.

20. (5) Size – (a) Petechial hemorrhages – 0.1-2 mm (b) Ecchymosis – 2-5 mm (c) Bruise – more than 5 mm. ***Size of a bruise >>>the surface of the weapon (as blood continues to ooze) (d) Hematoma – More than 5 mm with appreciable swelling. Forms a fluctuant mass by large vessel bleed (6) Margins – blurred (7) Extent – depends on the force

21. Types: (1) Intradermal bruise - occurs in dermis (Fig 12.9). Amount - of extravasated blood is small, pattern more clear (more superficial) occurs especially when the impacting object has alternating ridges and grooves (2) Subcutaneous bruise - Most common type of bruising (appears soon) (3) Deep bruise - deep subcutaneous tissue just above muscle, or between muscular bundles. apparent after 1-2 days after

22. Factors Modifying Size and Shape 1. Age Children and old people bruise 2. Sex Women bruise more easily than men [more s/c fat] 3. Obesity Fat people bruise more easily [greater amount of s/c fat] 4. Color of skin Fair skin- better appreciated visually 5. Effect of embalming dark pigment complex with blood 6. Condition and type of tissue ( i ) Vascular and loose tissue ( eg face, vulva, scrotum) (ii) Good muscle tone (boxers, athletes (ii) Resilient areas (abdomen, buttocks) bruise less.

23. 7. Weapon used : yielding weapon (less bruising ) 8. Associated diseases ( i ) Arteriosclerosis –rupture easily (ii) Blood dyscrasias –even on minor trauma (iii) Poisonings – Hepatotoxic poisons Chronic alcoholics 9. Miscellaneous factors If injured part is thickly clothed, bruising may not be seen Persons on anticoagulants, antiplatelet drugs, SSRI"More extensive bruising. SSRIs

24. Special bruise 1. Tram line bruise/ rail road bruise struck by a pliable instrument broom handle, cane appears as two parallel lines of bruising with an undamaged zone in the centre The intervening pale area = the width of the weapon

25. 2. Ectopic contusion/ Migratory bruise The site of bruise does not necessarily indicate the site of violence Extravasated blood tracks along fascial planes or between muscular layers under the influence of gravity to reappear at a site below the injured site it is known as ectopic, migratory or percolated bruise

26. Examples: ( i ) Spectacle hematoma – (a) Blunt injury to the forehead collects around the eye (b) Blunt injury to skull / fracture of anterior cranial fossa known as spectacle hematoma, panda eyes or raccoon eyes (ii) Battle sign – Bruise behind the ear [mastoid ecchymosis] may indicate fracture of posterior cranial fossa

27. (iii) fracture of jaw – “bruise in neck” (iv) fracture of pelvis – “bruise in thigh” fracture of femur - lower outer aspect of thigh (vi) Blunt injury to upper part of thigh- above knee (vii) Kick on the calf- around ankle. (viii) Gray Turner’s sign – retroperitoneal hemorrhage, pancreatitis (ix) Cullen’s sign – retroperitoneal or intra-abdominal haemorrhages

28. Age of bruise Duration Colour Pigment 1 Initially Red Oxy hemoglobin 2 Few hours- 3days Blue Deoxy hemoglobin 3 4 th day Bluish black- brown Hemosiderin 4 5-6 days Green Hematoidin 5 7-12 days Yellow Bilirubin 6 2 weeks Normal Oxyhemoglobin

29. Special situations: ( i ) Subconjunctival bruising – color changes do not occur. They change straight from red to yellow (ii) CO poisoning – bruise have a cherry red color.

30. Postmortem bruise Antemortem bruise Postmortem bruise Time of appearance Before life Within 2-3 hours of death Swelling around Present Absent Damage to epithetlium Present after Size Small to large Always small Extravasation More less Site anywhere Bony prominences Tissue underneath Staining +++ Washes off easily with water Histology Inflammatory reaction + nil Colour changes + Always dull blue Histochemistry Enzymes++ ----

31. Artificial bruise True bruise Artificial bruise Cause Blunt force Irritant juices Site Anywhere Exposed accessible parts Colour Changes with time Dark brown Shape ovoid irregular Margins Regular diffuse Distinct irregular Itching No Yes Vesicles No Present Redness and inflammation Seen over the lesion Seen around the lesion Contents Extravasated blood Acrid serum Chemical tests ------ +++++

32. Postmortem staining vs contusion Postmortem staining Contusion Dependent portions anywhere Postmortem change Caused by Blunt force Confined to the vessels Infiltration in deep tissues Margins- defined Blurred margins Blanch test +++ Does not blanch Incision- blood in vessels Incision- blood infiltration Area not elevated Area elevated Enzyme histochemistry – enzymes++ No enzymatic activity

33. Medicolegal importance Age of bruise –Can confirm or refute the story of victim Alcoholics – are more prone to bruising Decomposition – can alter the appearance of contusions Distribution of bruises –indicate the character and manner of injury ( i ) Child abuse – of different ages all over the body (ii) Manual strangulation – 6 penny bruises (iii) Pinning on the ground -bruising of shoulder blades (iv) Restraint signs - wrists (v) Sexual assault – bruising of inner aspect of thighs

34. 5) Manner of production : ( i ) Self inflicted – Very rare because painful. May be seen in hysteria and mentally ill persons. (ii) Accidental – (a) Very common (b) Seen on prominences [forehead, nose, elbows, knees] (iii) Homicidal - (a) On any part of the body (b) Associated injuries

35. 6) Medicolegal value – medicolegally less valuable than abrasions because: ( i ) Ectopic bruises - appear away from the site of injury. (ii) Direction of force – not indicated (iii) Shape and size - does not correspond to weapon [due to oozing] (iv) Time of appearance –may be too long after infliction (v) Visibility - in dark skinned persons 7) Patterned bruises – May indicate the surface features of offending weapon 8) Size – can indicate the degree of violence.

36. Lacerations are tears or splits of skin , mucus membrane, muscle or internal organs, produced by application of blunt force to the body, which stretches tissues beyond their limits of elasticity .

37. Salient features : (1) Also called ruptures (2) Displacement of tissues is most common – when soft tissues are crushed against bone, e.g. scalp, facial bones, shoulders and shin.

38. General Characteristics (1) Margins – irregular, ragged, uneven (2) Edges : ( i ) Angular impact (a) side opposite to the direction of motion - torn free and undermined. (b) side from which blow was delivered -abraded and bevelled (ii) Perpendicular impact - Equal undermining on all sides. (3) Depth – depends on ( i ) degree of force (ii) depth of soft parts at the site of injury.

39. (4) Shape and size : ( i ) May not correspond - with the weapon (ii) Linear –long, thin objects eg crowbars, pipes. (iii) Irregular, ragged or Y-shaped –objects with flat surfaces (iv) if curved - convexity of curvature points towards the direction of force (v) Stellate [star shaped] – blunt round object (vi) Crescentic–blunt object with an edge, eg hammer head (vii) Semicircular –head against wall or other hard surface (convexity of head) (viii) Patterned lacerations

40. (ix) Swallow tails at one end – seen sometimes due to tearing at angles of lacerations

41. (5) Gaping – present due to pull of elastic and muscular tissues. (6) Bruising : in skin or s/c around the wound (7) Tissue bridges – at the base of wound Signature of a BLUNT FORCE deeper tissues [BV, connective tissue, elastic fibres , nerves etc ] are unevenly divided. (8) Hair bulbs – crushed

42. (9) Hair and epidermal tags – Deeply driven in the wound (10) Hemorrhage : less in laceration. vessels are crushed and blood clots readily (11) Foreign matter – usually present in the wound.

43. TYPES (1) Tear - the most general having sufficient amount of underlying fat and muscle ( eg thigh). (2) Split laceration skin direclty overlying a bone, with minimal amount of underlying fat and muscle. ( eg : scalp, shin of tibia) mimics an incised wound [called incised looking lacerated wound].

44. Tear laceration Split laceration

45. (3) Stretch laceration skin is overstretched, resulting in a large flap. Ex. a glancing kick by foot. (4) Cut laceration by heavy cutting weapons between a true laceration and a true incised wound. The edges of the weapon do cut the skin but since the edges are heavy, they crush and bruise the margins of the wounds too. Also called chop wounds (usually + fracture)

46. (5) Avulsion if grinding compression is applied, causing avulsion (separation) of large areas of skin from its underlying attachments ***also known as flaying

47. Incised wound Lacerated wound Edges Clean cut Ragged Margins Bruised Not bruised Injuries to underlying tissues (TISSUE BRIDGES+++) Clean cut Crushed Hair bulbs Clean cut crushed Bleeding More Less

48. Incised wound Incised looking lacerated wound Margins (under hand lens) Clean cut Ragged Edges Minimally bruised Heavily bruised Blood vessels at the base Cleanly cut crushed Subcutaneous tissue Cleanly cut Tissue bridges+++ Hair around the wound Cleanly cut Crushed

49. MLI (1) Age of lacerations – (very much irregular) ( i ) Fight - indicates time of struggle (ii) Disputed pregnancy - age of perineal lacerations (2) Extent of force (3) Extraneous material –may connect the injuries -place of occurrence

50. (4) Manner of production – ( i ) Accidental - falls etc (ii) Suicidal lacerations – are very rare, (painful and rarely effective) May be seen in suicidal jumping from high buildings. (iii) Homicidal – Lacerations on the vertex generally indicate homicide. Bagh Nakh [tiger claws] designed to lacerate skin and muscle.

51. (5) Shape of lacerations – rarely indicate the weapon. (patterned lacerations). Exceptions- Eg : chains (6) Tendons and muscle lacerations without corresponding lacerations on skin Can indicate violent muscular contractions and spasm ( convulsants ) lacerations in hollow viscera may also be seen.

52. It is a clean cut wound through the tissues caused by a sharp-edged instrument where length is its maximum dimension

53. Salient features : (1) Force delivered over a very narrow area corresponding with the cutting edge of the instrument (2) Skips in pattern ( i ) when there are bony ridges (ii) tendons or (iii) over areas of loose wrinkled skin

54. Characteristics 1. Length  (1) Greatest dimension (2) No relation to the cutting edge of the weapon (may be drawn to any distance) 2. Width  may be greater than the edge of weapon due to retraction of divided tissues 3. Margins  (1) Clean-cut, well-defined (2) if knife is serrated – may produce a saw-toothed cut (3) Edges - usually everted (sometimes inverted – eg : scrotum)

55. 4. Abrasions and contusions – only if it is perfectly sharp 5. Shape (1) usually spindle shaped – retraction of edges (2) Crescentic – if blade is curved or struck surface is convex (3) Zigzag – if skin folds are loose 6. Gaping – is greater if muscle fibres are cut transversely or obliquely [due to retraction].

56. 5. Direction (1) deeper at the beginning because more pressure is applied on the knife at this point. (head) (2) become increasingly shallow towards the tail The portion where the epithelium alone is cut is known as tailing of the wound.

57. 6. Beveling cut refers to a cut which is not perpendicular to the skin surface, but at an angle Direction of weapon: (1) Vertical –edges of wound would make a nearly 90° angle with the skin surface (2) Oblique one edge - an angle >90° with the skin surface (beveled edge) The other edge -makes an angle <90° with the skin ((under mined edge) (3) Nearly horizontal –a wound with a flap is produced. usually indicates homicide, and may indicate relative position of the assailant and victim.

58. 7. Hemorrhage (1) Hemorrhage is more as the vessels are cut cleanly. (2) Spurting will occur if an artery has been cut.

59. SUICIDAL CUT THROAT HOMICIDAL CUT THROAT Left side of neck (in right handed) Rarely crosses to opposite side Usually on both sides High above thyroid cartilage Low below thyroid cartilage Ragged edges Sharply cut edges Hesitant cuts +++ Single deep wound Tailing present Absent Less severe Severe Jugular vein injured >> Carotid CAROTID +++ JUGULAR

60. SUICIDAL CUT THROAT HOMICIDAL CUT THROAT Weapon – Present at the scene Weapon – always absent Clothes- not damaged Clothes- torn Hands- cadaveric spasm holding weapon --- Defence wounds- absent Defence wounds + palms, wrists Circumstantial evidence– depressed, room locked from inside

61. Age of Incised Wounds 1. Gross (1) Fresh – Hematoma formation (2) 12 h – ( i ) Edges red, swollen, adherent with blood and lymph (ii) Leukocytic infiltration (3) 24 h – Dried clot in the form of crust or scab. 2. Histopathology Few min Dilatation of capillaries ,Margination and emigration of neutrophils 12 h to 24h–fibroblasts + Monocytes appear in exudate 72 h – Formation of vascularized granulation tissue 4-5 d – New fibrils are formed 1 wk – scar formation if wound is small

62. MLI of Incised Wounds (1) Reconstruction of crime (a) the nature of the weapon – sharp edged (b) Age of injury and (c) Direction of force (2) Body with incised wounds immersed in water soon after death - Blood is lysed by water. It is difficult to make out if the wounds were AM or PM. (3) Manner of injury –may be accidental, suicidal or homicidal.

63. A stab wound is one which has depth as its maximum dimension It is produced when force is delivered along the long axis of a narrow or pointed object into the depths of the body.

64. Punctured wound is a stab wound caused by a circular pointed smaller shaped object. Insertion of pins, needles Snake bite Drug addiction Needle punctures are a common method of infanticide (through anterior or posterior fontanelles).

65. Penetrating wound enters into a body cavity without coming out. Should be described in a sequential order, i.e. entrance wound, depth and direction of track specific location of termination Ex - ( i ) Stab wound to the chest or abdomen [having no exit] (ii) Gunshot wound to the head [having no exit

66. Perforating wound has both an entry and exit wound and firearm wounds; in a sequential order as above, i.e. entrance wound, path of wound, exit wound

67. Characteristics 1. Length stab wound ‘l’ is normally less than width ‘w’ of weapon. 2. Width may not indicate the true thickness of blade, because of retraction of wound edges, 3. Margins (1) If weapon has sharp edges  Margins are clean cut [incised stab wound] (2) If weapon has rounded edges  Margins are contused and lacerated [lacerated stab wound]. 4. Depth (1) Greatest dimension - Depth is the greatest dimension in stab wounds. 5. Shape which runs across the lines of Langer wound causes gaping; a parallel /an oblique cut - a crescentic or semicircular wound

68. Shape of the entry wound- depends on the weapon

69. Complications (1) Air embolism – especially in stabs of neck vessels (2) Choking due to inhalation of blood (3) Hemorrhage (4) Infection (5) Pneumothorax.

70. MLI of Stab Wounds (1) Concealed puncture wounds – used homicidally. (2) Depth of wound – indicates force used (3) Direction and dimension of wounds – Indicate relative positions of assailant and victim (4) Manner of production (5) Multiplicity of wounds - revenge murders (6) Shape of wound – Indicates weapon (7) Time of attack –the age of stab wound

71. DEFENCE WOUNDS OFFENCE WOUNDS

72. SELF-INFLICTED INJURIES Therapeutic wounds