Mechanical injuries_Forensics


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Mechanical injuries_Forensics

  1. 1. Mechanical injuries Injuries caused by sharp cutting weapons
  2. 2. This is what we will see 1. Classification of injuries 2. Injuries caused by sharp cutting objects
  3. 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. 4. Our interest is in • Injuries due to sharp cutting weapons • Incised wounds • Chop wounds • Stab wounds
  5. 5. Incised wounds • Causes • Characters • Age • Histopathology • Medicolegal importance • Special topic- Wounds by glass
  6. 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. 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. 8. Characters • Width • Greater than edge of weapon (due to retraction of divided tissues and shaking of blade)
  9. 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. 10. Characters • Shape • Usually Spindle shaped • Zig-zag if skin is loose as in axilla • Crescentic if present on convex parts like buttocks
  11. 11. Characters • Hemorrhage • More due to cleanly cut vessels • Spurting of artery when cut is characteristic
  12. 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. 13. Characters • Beveling cut • If blade enters obliquely • Tissue visible at one margin and other margin is beveled (overhanging or undermined)
  14. 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. 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. 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 1 2 3 4
  17. 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. 18. Chop wounds • Causes • Characters • Features • Medicolegal importance
  19. 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. 20. Characters • Margins • Sharp • May show slight abrasion • Ragged and bruised (if edge is blunt) • Marked destruction of underlying organs
  21. 21. Characters • Dimensions • They are deep gaping ones. • The dimensions of wound correspond to cross section of penetrating blade.
  22. 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. 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. 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. 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. 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. 1 2 3
  27. 27. Stab wounds • Causes • Characters • Complications • Examination of wound • Examination of weapon • Medicolegal importance • Special topic- Concealed puncture wound & Incised stab wound
  28. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 1 2 3 4 5 6
  43. 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. 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. 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