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
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.

9. 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.

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
Also lead

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
nitroglycerine

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.
Pink to blue is positive for lead residues

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
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

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

29. 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.

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 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

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