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Gunshot Wounds

Gunshot Wounds. Tissue Disruption. Two Principle Mechanisms Low velocity High velocity. Low Velocity Tissue Disruption. Direct laceration of the tissues (drilling effect). Causes the permanent cavity seen at autopsy Used to follow path of bullet. High Velocity Tissue Disruption.

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Gunshot Wounds

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  1. Gunshot Wounds

  2. Tissue Disruption • Two Principle Mechanisms • Low velocity • High velocity

  3. Low Velocity Tissue Disruption Direct laceration of the tissues (drilling effect). • Causes the permanent cavity seen at autopsy • Used to follow path of bullet

  4. High Velocity Tissue Disruption There is an additional effect of temporary cavity formation • Cavity maybe 30x the diameter of the projectile • Has a lifespan of 5 to 10 milli-seconds • Organs which are dense and inelastic may burst. Ex. - liver • Wounds of the head produce bursting injuries of the skull

  5. Shot in Skull

  6. Other Wounding Mechanisms • Shockwaves from the projectile may cause the rupture of gas filled organs. Ex-bowel • Secondary projectiles. Ex. - bone fragments or bullet fragments

  7. Ammunition Type & Wound Patterns • Full Metal Jacket • Partial or No Metal Jacket

  8. Full Metal Jacket Wound Patterns • Military style ammunition • Lead bullets jacketed with harder metal (copper) • Passes through the body and exits

  9. Partial or No Metal Jacket Wound Patterns • Lead bullets • Deforms as passing through the body

  10. X-Rays for Gunshot Wounds X-rays should always be performed in GSW • Is the projectile present? • If present, where is it located? • If the projectile exited, are fragments present and where are they? • What type of ammunition or weapon was used? • What was the path of the projectile?

  11. X-Rays

  12. Gunshot Suicide • The majority of suicides do not leave notes • A contact wound creates a presumption of suicide not accident • Suicide by multiple gunshot is uncommon but not rare • A suicide victim may test fire the weapon • In about 20% of suicides the weapon is found clutched in the hand

  13. Gunshot Suicide Contact Wound

  14. Gunshot Suicide Wound Distribution

  15. Gunshot Suicide Wound Location • An unusual location raises the presumption of homicide • Occasionally blood spatter will be deposited on the hands firing or steadying the gun

  16. GUN SHOT RESIDUE

  17. What is Gun Shot Residue? • Tiny particles of primer and gunpowder (GSR) are expelled when the gun is fired • Not water soluble • Can be dislodged by blood or rough handling

  18. How is GSR detected? • Primer is generally made up of barium nitrate and antimony sulfide • Most GSR detection techniques concentrate on barium and antimony

  19. How is GSR detected? GSR Chemical Tests • Griess Test. • Will not interfere with later tests for lead residues • Detect the presence of nitrite residues • Primary test used by forensic investigators

  20. How is GSR detected? GSR Chemical Tests The Griess Test

  21. How is GSR detected? GSR Chemical Tests • Sodium Rhodizonate Test • Determines if lead residues are present on the exhibit.

  22. How is GSR detected? Entomology • Examiners can extract GSR from the larvae that had been feasting on the body of someone involved in, or that was in proximity to a shooting

  23. Can GSR Convict Someone? • All the shooter has to do is wash his hands thoroughly, although normal human movement and activity can dislodge the particles • Most labs will not test samples collected more than 6 hours after the shooting • Shooter’s hands are bagged

  24. Can GSR Convict Someone? • Barium and antimony can also be found in firecrackers, paint, and some industrial settings • Many other factors involved—weather (including wind), sweating skin, dry skin, putting hands in pockets, washing, etc

  25. Can GSR Convict Someone? • FBI is no longer analyzing gunshot residue • Could become a weapon for defense attorneys in pending cases and in efforts to overturn convictions

  26. Clothing Distance Determinations • Entrance Holes: • Typically have very even margins • Smaller in diameter than the bullet due to the elasticity of the fabric

  27. Clothing Distance Determinations

  28. Clothing Distance Determinations • Exit Holes: • Usually provide no evidence • Usually wider than the actual diameter of the bullet

  29. GSR Deposits • The further gunshot residues travel from the muzzle, the broader and less concentrated the pattern becomes. 

  30. GSR Deposits • GSR travels 3-5 feet in most firearms • At the 3-5 foot range the gunshot residues may only consist of a few trace particles • At around 18-24 inches most firearms will start to deposit considerable concentrations of GSR • At distances of less than 12 inches heavy concentrations of visible gunshot residues will normally be deposited

  31. GSR Distance Standards • Made by firing the firearm, using ammunition like that used in the actual case, into witness panels that consist of  white pieces of cotton twill jean cloth • Several panels will be fired into at varying distances

  32. GSR Distance Standards

  33. Ballistic Gelatin • Used by the shooting industry to simulate soft body tissue • Provides an alternative to animal or cadaver testing.

  34. FUN! • Go to www.firearmsid.com • Scroll over “Classroom” • Click on Student Login • Login Key: C18798Forensics08 • Full Name: Your’s & Partner’s names • Click on Cartridge Case ID-VCM

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