Mechanical injuries_Forensics

1. Mechanical injuries Injuries caused by sharp cutting weapons

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

3. Injuries are classified in 3 ways Simple Grievious MEDICOLEGAL LEGAL MEDICAL 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 INCISED WOUNDS

7. Characters INCISED WOUNDS 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 ) INCISED WOUNDS

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

10. Characters INCISED WOUNDS 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 INCISED WOUNDS

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

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

14. Age of incised wound INCISED WOUNDS

15. Histopathology INCISED WOUNDS

16. Medicolegal importance INCISED WOUNDS 1 2 3 4

17. Wounds by Glass INCISED WOUNDS 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 CHOP WOUNDS

20. Characters Margins S harp May show slight abrasion R agged and bruised (if edge is blunt ) Marked destruction of underlying organs CHOP WOUNDS

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

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. CHOP WOUNDS

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 CHOP WOUNDS

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 . CHOP WOUNDS

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 . CHOP WOUNDS

26. Medicolegal importance CHOP WOUNDS 1 2 3

27. Stab wounds Causes Characters Complications Examination of wound Examination of weapon Medicolegal importance Special topic- Concealed puncture wound & Incised stab wound

28. Causes W hen 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 STAB W OUNDS Long axis

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. STAB W OUNDS

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 . STAB W OUNDS

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. STAB W OUNDS

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 STAB W OUNDS

33. Characters STAB W OUNDS

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 STAB W OUNDS

35. Characters- Shape D ouble-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. STAB W OUNDS

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 . STAB W OUNDS

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. STAB W OUNDS

38. Characters Direction In solid organs , t he 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. STAB W OUNDS

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. STAB W OUNDS

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. STAB W OUNDS

41. Examination of weapon The doctor should note : Length , width and thickness of the blade, W hether 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. STAB W OUNDS

42. Medicoloegal importance STAB W OUNDS 1 2 3 4 5 6

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. STAB W OUNDS 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   STAB W OUNDS SPECIAL TOPIC

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