1. Ballistics
Chapter 15

2. The Beltway Snipers page 506
Read the Beltway Snipers on page 506 from textbook.
In an outline answer the 5 W’s.
Who were they?
What did they do?
Where did it happen?
When did it happen?
Why did they do it?

3. Firearms Examiners Ballistics expert:
-study bullets
-gun operation
-serial numbers
-gun powder residue
-shooting distance. -
Forensic firearms examiners – are involved in crimes involving shootings or projectiles
Ballistics - the science of the mechanics that deals with the flight, behavior, and effects of projectiles

4. Classification of guns
Handguns – Held in one hand
Revolvers - a handgun having a rotating chambered cylinder for holding a number of cartridges, which may be discharged in succession without reloading.
Semiautomatic pistols – Fire once when trigger is depressed
Machine pistols – Fire continously as long as the trigger is depressed

5. Shotgun - a smooth bore gun for firing small shot
Rifles - a shoulder firearm with spiral grooves cut in the inner surface of the gun barrel to give the bullet a rotatory motion and thus a more precise trajectory.
Shotgun - a smooth bore gun for firing small shot
Shot is smaller beads inside a cartridge that dispersed in a circular pattern

6. The Gun Barrel
The inner surface of the barrel of a gun leaves markings on a bullet which are unique to each gun.
Rifling are the spiral grooves formed in the bore of firearm barrel which create spin on a bullet.

7. The surfaces of the original bore remaining between the grooves are called lands.

8. Determining Caliber
Caliber is the diameter of the bore of a rifled firearm. Measured in hundredths of an inch or millimeters
EX: .22 caliber or 9mm

10. Comparisons
Firing Pin Impressions—the base of the casing shows where the firing pin struck which helps ID the type of gun
Breechblock patterns are created in the back of the firing wall when the bullet casing is forced against the back of the breechblock leaving an impression on the casing

11. Comparing Ballistic Evidence
The FBI maintains a database known as the General Rifling Characteristics File to help with land, groove, and twist characteristics of known weapons.
Databases of information assist in ballistic fingerprinting

12. Ballistics Databases Bureau of Alcohol, Tobacco, and Firearms (BATF)
DRUGFIRE was developed by the FBI to focus on shell casings and bullet striation patterns
The Integrated Bullet Identification System (IBIS) maintained by the BATF to match bullets or casings found at crime scenes.

13. Gunpowder Residue
Chemicals and particulates from explosive gases released when a weapon if fired are called gunshot residue (GSR)
GSR clings to the shooter’s hand, arm, and clothing or other close surfaces.

14. Infrared photography can reveal GSR
A Griess test may reveal patterns of GSR
Photographic paper is pressed over the area and immersed in a reagent that reacts with inorganic nitrates in the GSR

15. Distance Determination
Distance Determination is the process of determining the distance between the firearm and a target, usually based on the distribution of powder patterns or the spread of a shot pattern.
Often test firings are made at different distances to compare residue patterns on test garments to those found on the victim.