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Crime Scene Reconstruction

Crime Scene Reconstruction. Glass . Blood. Laminated Glass .

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Crime Scene Reconstruction

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  1. Crime Scene Reconstruction Glass Blood

  2. Laminated Glass

  3. Laminated Glass is made up of a vinyl laminate (PVB) layer bonded together between two panes of glass under heat and pressure. Laminated glass may crack upon impact, however the glass fragments typically stick to the protective inter-layer rather than falling free and potentially causing injury. It breaks exactly like the windshield of your car, cracks but is held in place by the vinyl laminate layer.

  4. Tempered Safety Glass

  5. The "heat-treatment" process of tempered glass provides safety characteristics giving it additional strength, resistance to thermal stress and impact resistance. Additionally, when fully tempered glass breaks it fractures into small, relatively harmless fragments. And markedly reduces the likelihood of injury to people as there are no jagged edges or sharp shards.

  6. Annealed/Ordinary Glass

  7. Glass Fracture from Bullets

  8. Blood Stain Patterns • 1. Low Velocity Impact • Droplets • Cast offs 2. Medium Velocity Impact • Spatter from weapon’s impact • Arterial spurts 3. High Velocity • Spray from weapon exiting body • Exhalation of blood

  9. Bloodstain EvidenceMay reveal: • Origin(s) of bloodstain • Distance of bloodstain from target • Direction from which blood impacted • Speed with which blood left its source • Position of victim & assailant • Movement of victim & assailant • Number of blows/shots

  10. Blood Spatter • Low velocity • e.g. free-falling drops, cast off from weapon • Medium velocity • e.g. baseball bat blows • High velocity • e.g. gunshot, machinery

  11. Low Velocity Blood Spatter • Blood source subjected to LV impact • Spot diameter: mostly 4 - 8 mm • some smaller, some larger • Free-falling drops (gravity only) • Cast off from fist, shoe, weapon • Dripping • Splashing • Arterial spurting

  12. Height Fallen Single drops of blood falling from fingertip onto smooth cardboard from various heights. No change in diameter beyond 7 ft. Adapted from Introduction to Forensic Sciences, W. Eckert, CRC, 1997

  13. 80 90 10 60 50 40 70 20 30 14 Angle of Impact Gravitational dense zone at lower edge Adapted from Introduction to Forensic Sciences, W. Eckert, CRC, 1997

  14. Origin Height above point of convergence 85 60 45 30 Distance from point of convergence length Point of Origin width Angle of impact = arc sin W/L

  15. Cast-off from Weapon • First blow causes bleeding • Subsequent blows contaminate weapon with blood • Blood is cast-off tangientially to arc of upswing or backswing • Pattern & intensity depends on: • type of weapon • amount of blood adhering to weapon • length of arc

  16. . . . . . . . . . . . . . . . . . Drip Pattern • Free-falling drops dripping into wet blood • Large irregular central stain • Small round & oval satellite stains . . . .

  17. Blood dripping into itself from height of 1 m (8 drops) Drip 2 39

  18. Dripping onto steps

  19. Tail of elongated stain points in direction of travel . Tail of wave cast-off points back to parent drop Parent drop wave cast-off Wave Cast-off

  20. Medium Velocity Blood Spatter • Blows with weapon (e.g. baseball bat)

  21. Downswing of Hammer

  22. Cast-off from Weapon ceiling

  23. Overhead swing with bloodied metal bar

  24. Cast-off PatternHow many strikes?

  25. Cast off Patternans: 4 (first strike causes bleeding) 1 2 3

  26. Cast off Pattern How many strikes?

  27. Cast off Pattern ans: 4 1 (4 spots) 2 (3 spots) 3 (2 spots) If weapon does not pick up more blood, spatter from subsequent backswings becomes progressively less. In practice weapon picks up more blood with each successful blow.

  28. Three overhead swings with hatchet

  29. Cast-off Pattern? Object

  30. Cast-off Patternfrom Hand

  31. Cast-off pattern from bloodied hand swung in front of target 6” ruler

  32. Cast-off & medium velocity spatter

  33. Cast-off & medium velocity spatter 2

  34. Arterial Spurt Pattern • Blood exiting body under arterial pressure • Large stains with downward flow on vertical surfaces • wave-form of pulsatile flow may be apparent

  35. Small arterial spurt spatter broken pottery

  36. Neck incisions (scene)

  37. Neck incisions ‘Hesitation’ injuries Probe in carotid artery Thyroid cartilage

  38. Medium velocity blood spatter.Point of impact 15 cm in front of vertical target surface 6” ruler

  39. High Velocity Blood Spatter • Blood source subjected to HV impact • Fine mist • Some larger droplets reach further • Gunshot • back-spatter from entry wound • forward spatter from exit wound • High speed machinery

  40. bullet exits foam Bullet enters foam bullet Gunshot: back& forward spatter Bloodstained foam held just above target surface. Bullet passing L to R just above sheet Back-spatter on entry Forward spatter on exit

  41. Gunshot Back Spatter • Arises from entrance wound • Passes back towards weapon & shooter • Seen only at close range of fire • Seen on: • inside of barrel • exterior of weapon • hand, arm, chest of shooter

  42. Back spatter on steadying hand

  43. Gunshot Forward Spatter • Arises from exit wound • Passes forwards in same direction as shot • More copious than back-spatter • Can be seen at any range of fire • Seen on nearby surfaces, objects, persons • especially on wall behind victim

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