1. Firearm Identification
Ballistics
Firearm Identification

2. THE SCIENCE OF FIREARMS IDENTIFICATION INCLUDES:
Comparison of bullets and cartridge casings
As well as:
Knowledge of all types of weapons
Restoration of obliterated serial numbers on weapons
Detection and characterizations of gunpowder residue on garments / around wounds / hands
Estimation of muzzle-to-target distances

3. Ballistics is the study of the trajectory taken by bullets!

4. There are literally thousands of types of firearms
There are literally thousands of types of firearms! They can be classified as shoulder firearms (rifles and shotguns) and handguns (pistols, revolvers, etc)

6. Revolver

7. Semiautomatic

9. Firearms can also be classified as “smoothbore” (shotguns) or “rifled” (most other weapons)

10. A gun barrel is produced from a solid bar of steel by drilling
A gun barrel is produced from a solid bar of steel by drilling. The manufacture of a barrel also requires the impression of spiral grooves on the inner surface. This is called “rifling”. The surfaces of the original bore are called lands. The diameter of a gun barrel, measured land to opposite land is called the “caliber” of the weapon. It is measured in hundredths of an inch or in mm
The lands and grooves guide the bullet through the barrel, giving it spin, so that it does not tumble, thus increasing its speed and force

11. CALIBER

12. Land
Groove
Caliber
Land
Groove
If this is a land
Impression, what are
The other areas?
Groove
Land

13. Every firearms manufacturer chooses a rifling process, giving the weapon class characteristics. Frequently, a firearms examiner is given a spent bullet without a weapon. The caliber, weight, etc. help determine the weapon. The FBI maintains a record of class characteristics known as the GRCF (Gallery Rifle Centre Fire).

14. Bullets

15. Full Metal Jacket vs Hollow Point
Some bullets are described as full metal jackets (FMJ) and some are described as hollow points (HP).
A hollow point is designed to stay inside the victim, as to not potentially exit the victim and strike someone else.
These bullets are often used by police so that other spectators aren’t injured.
A full metal jacket is designed to pass through the victim.

16. Bullet Types

17. The marks or striations on the inner surface of the barrel are randomly irregular and make each unique. As the bullet passes through the barrel, its surface is impressed with unique rifled marks of the barrel.
There are small changes due to grit, dust, & wear.
Recovered evidence bullets may become so distorted on impact as to yield only a small area with markings.

18. 22 caliber copper-washed and plain lead bullets.
9mm LUGER caliber G.F.L. (Fiocchi) FMJ bullets.
32 S&W LONG caliber plain lead bullet.
                            
38 SPECIAL caliber plain lead bullet.

19. A comparison microscope is used to compare striation marks
A comparison microscope is used to compare striation marks. No rules govern the points needed for bullet comparison.

20. A bullet is slightly larger in diameter than the bore diameter of the barrel in which it is designed to be fired.  The bore diameter is the distance from one land to the opposite land in a barrel.  As a result, a rifled barrel will impress a negative impression of itself on the sides of the bullet like those seen below.  

21. Water tank
Weapons are test fired into a recovery tank containing water

22. Pulling the trigger serves to release the weapon’s firing pin, causing it to strike the primer, which ignites the powder. The burning gunpowder generates gases that expand and propel the bullet forward, and the spent cartridge case back against breechback. The shell therefore also has unique markings!

23. Bullet and cartridge case identification through comparison microscope
                                                                                                                        
Bullet and cartridge case identification through comparison microscope

24. Comparison microphotograph of two bullets

25. Land Impression Striations
380 AUTO caliber FMJ bullets
fired from a EAA Corp. pistol.
9mm LUGER caliber FMJ bullets
fired from a BROWNING pistol.

26. Groove Impression Striations
38 SPECIAL caliber SJHP bullets
fired from a TAURUS revolver.
38 SPECIAL caliber
lead bullets
fired from a ROHM revolver.

27. A shotgun shell is diagrammed below:
Gauge: Refers to the diameter of the barrel on a shotgun in terms of the number of lead balls the size of the bore it would take to weigh one pound (10 gauge, 12 gauge, etc.) ".410 gauge" really refers to caliber, but is worded as such to refer to a shotgun.

28. Bullets, shot pellets, and other projectiles may be recovered from the crime scene or from the bodies of shooting victims. Fired cartridge cases, fired shot shells, shot shell wadding, unfired ammunition and components may also have evidentiary value.

29. Types of Breech Marks Circular Parallel breech marks Mottled

30. cases fired in a COLT pistol.
Breech marks do not match
Matching breech marks
38 SUPER AUTO cartridge
cases fired in a COLT pistol.
Firing pin impressions

31. Drugfire Computerized Firearms Comparison System
                                                                           
Drugfire Computerized Firearms Comparison System

33. Gunshot residue patterns.
The deposition of gunshot residue on evidence such as clothing varies with the distance from the muzzle of the firearm to the target. Patterns of gunshot residue can be duplicated using a questioned firearm and ammunition combination fired into test materials at known distances. These patterns serve as a basis for estimating muzzle-to-garment distances.
                                                                                                              
Gunshot residue patterns.

34. Muzzle Blast of a Shotgun

35. T-shirt chemically treated for the presence of lead residue
T-shirt chemically treated for the presence of lead residue. Heavy deposits of lead found along left shoulder.

36. Close-up of bullet entrance hole in above shirt
Close-up of bullet entrance hole in above shirt.   Lead bullet wipe residues (pink) noted around the hole.

37. 9-inch test standard showing visible particulate residue (lead, burned and unburned gunpowder) and vaporous lead (pink) residues.

38. 3-inch test standard showing a very concentrated  deposit of soot and vaporous lead residues.
Griess Test from the 3-inch test standard.  Orange color is a positive reaction to a presence of a pattern of nitrite residues.

40. Soot is seen on the hand of a suicide victim, giving an indication that he was holding the weapon when it was fired.

41. Collection and Preservation of Firearms Evidence
Never stick an object into the barrel
Pick up the gun by the edge of the trigger guard or on the checkered portion of the grip – these areas do not usually retain prints
Weapons recovered in water must be transported to the lab in the same water in order to prevent rusting in transit
Ammunition must never be dug out of a wall or other surface – remove the whole section surrounding the bullet in order to reduce the possibility of adding any stray scratches, etc.