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 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

Shot in Skull

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

Ammunition Type & Wound Patterns Full Metal Jacket Partial or No Metal Jacket

Full Metal Jacket Wound Patterns Military style ammunition Lead bullets jacketed with harder metal (copper) Passes through the body and exits acketed bullets- Jacketed bullets are a laminate of material, with the harder "jacket" covering a core typically made of lead.  This jacket material differs from the thin copper plating seen on the copper-washed bullets above.  The jacket material cannot be easily removed. The most common bullet jacket material is copper.  These can sometimes be plated with nickel to give the bullet a silver finish but the jacket can also be made of a number of other materials such as aluminum or steel.  Steel jackets are widely used in bullets that originate in the European and Chinese markets.  Steel jacketed bullets are usually coated or plated to help prevent rusting.

Partial or No Metal Jacket Wound Patterns Lead bullets Deforms as passing through the body Non-jacketed Bullets- The most common material used in the manufacture of non-jacketed bullets is lead.  Lead bullets are usually an alloy of lead and antimony which is added to give the bullet some additional hardness.  Variations are the norm when it comes to the materials used in bullets and it's not uncommon to find lead bullets with a thin coating of copper or brass plating.  Bullets having this thin coating is sometimes referred to as a copper-washed or "Lubaloy" bullet.  This thin coating can be easily scratched away from the surface of the lead causing problems for firearm examiners when these bullets are damaged.  Another example of a coated bullet is the Federal "Nyclad" bullet that is designed to reduce lead emissions.

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?

X-Rays

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

Gunshot Suicide Contact Wound

Gunshot Suicide Wound Distribution

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

GUN SHOT RESIDUE

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

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

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 nitroglycerine

How is GSR detected? GSR Chemical Tests The Griess Test

How is GSR detected? GSR Chemical Tests Sodium Rhodizonate Test Determines if lead residues are present on the exhibit. Pink to blue is positive for lead residues

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

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

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

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

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

Clothing Distance Determinations Holster, the higher the velocity – the more damage to the garment, Bullet fragments Bullets shot from an angle has an elongated hole in garment Angled grazing bullet Bullet wipe residue – lead from bullet wiped off on garment

Clothing Distance Determinations Exit Holes: Usually provide no evidence Usually wider than the actual diameter of the bullet No bullet wipe residue

GSR Deposits The further gunshot residues travel from the muzzle, the broader and less concentrated the pattern becomes.  Because the various elements included in gunshot residues are very small and lack mass they lose their energy rapidly.

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 Gunshot residue is normally a combination of gunpowder residues and lead residues Modern – smokeless powder

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

GSR Distance Standards

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

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