Anth 245 1st Edition Lecture 10Outline of Last Lecture- Sharp force trauma in soft tissue (4 types) - ID of weapon - MOD - Defense wounds Outline of Current Lecture- Gunshot Wounds- Factor affecting loss of kinetic energy- GSW- Problems in determining range of fire- Manner of death- Take home pointsCurrent LectureGunshot Trauma Gunshot Trauma (GSW) vs. BFT - BFT is slow velocity - GSW is high velocity (feet per second) o Bones act as brittle due to high velocity of the bullet o Stress-Strain curve does not apply o No elastic or plastic deformation  Linear fracture lines from entrance wound can beart bullet to site of the exit wound (fractures happening faster than bullet is traveling) o 9-10,000 victims a year of homicide by firearms in the U.S. Gunshot Wounds - Wounding power corresponds to the kinetic energy dissipated o Quicker loss of velocity means greater damage o Bullet from a 9mm pistol: 1,100 ft/second - Mechanisms of wounding o Creation of cavities inside the tissues due to energy transferred Temporary and Permanent Cavities- Temporary cavity - tunneling of bullet with tissue expansion on each side leading to massive tearing of immediate and remote tissues - Permanent cavity: wound track which remains in tissue after temporary cavity has disappeared o Much larger in high velocity bullets Factors affecting loss of kinetic energy - Amount of kinetic energy the bullet possesses at the time of impact o Caliber, construction, configuration of bullet o Angle of yaw at time of impact  Yaw = deviation along the long axis of the bullet (fish tailing) o Tumble - end over end o Tissue characteristics GSW - Soft Tissue o Determine trajectory of fire o determine range of fire - Bone o Determine trajectory of fire o Determine minimum number of wounds and sequence o Fracture lines do not cross o Can't tell range of fire from bones - Entrance wounds - skin o Small, round hole; creates abrasion o Soot and other material present based on distance to gun o Small amount of blood - Entrance wounds - Bone o Reverse cone - shaped after defect (internal beveling) o Creates radiating fractures - Exit wounds - Bone o Reverse cone from entrance wound with beveling on external surface o Radiating fractures from entrance wound - may beat bullet to opposite side - Exit wounds - Skin o More massive and irregular than entrance wounds o Skin rips o Excessive blood and tissue loss - Range of Fire o Distance between gun's muzzle and injury (soft tissue) o As distance increases, lose flame, then smoke, then soot, then powder Travels least Fire --> Smoke --> Soot --> Powder --> Bullet travels furthest3 Primary categories: - Contact - Intermediate - Distance Contact wounds - Hard contact: Muzzle held tightly against skin o Laceration of wound edge over bone o Smooth circular defect over soft tissue o Muzzle imprint o Soot and powder in wound tract - Loose contact o Charring of wound margins Intermediate Wounds - Tattooing o Abrasions or contusions die to burning powder doesn't wash off o Soot and powder on skin Distant Wounds - No tattooing or soot deposition - Only bullet reaches victim Problems in determining range of fire - Decomposed body - Soot, tattooing, etc. evidence is lost - Short-term survival after injury o Hospital cleans wounds o Healing and cleaning obscures evidence - Intermediate targets - E.g. cars, ricochet, re-entry Direction of Fire - Determine from spatial (straight-line) relationship of entrance and exit wounds - Three dimensionso Anterior to posterior o Right to left o Superior to inferior Manner of Death - Homicide, suicide, accidental, all possible - Evaluation of range of fire - Trajectory and location of entrance wounds - Position of gun and body - Lethal area of body - GSR on the hand - Multiple bullet wounds do not rule out suicide - Shotgun wounds also do not rule out suicide - "Accidental" rests on investigation - Pathologist/ME makes final call Caliber Determination - highly unreliable from wound morphology - Skin and bone are too elastic Take Home Points - Wounding potential is from the loss of kinetic energy - Temporary and permanent cavities - High velocity, therefore bone acts brittle Determine angle of fire, direction of fire,