1. DECEMBER 8, 2015 EQ: How is bullet analysis & comparison used to identify weapons used to commit a crime? WARM-UP: (DC snipers news) View the following video clip on the “Beltway Snipers” and write and answer the following questions. 1. According to the video, how many people were killed? 2. Who was responsible? 3. What was their motive? 4. What were the consequences? 5. Were there any regrets from the accused? If so, what?
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2. Bullet Analysis & Comparison
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3. Bullets to Guns
It is extremely difficult to convict some one of a murder without possession of the murder weapon.
In the case of a shooting, matching a bullet with a gun is essential in most cases.
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4. Ballistics
Characteristics of ammunition, firearms, and residue are examined to find matches between suspects and the evidence found at a crime scene.

5. Chemical tests can reveal gunshot residue (GSR) on the hands, face, or clothing of a victim or suspect to indicate how close a person was to a fired gun.

6. Gunshot Distance Analysis

7. Rifling (grooves) in a gun barrel causes distinctive grooves, indentations and scratches upon fired bullets, which can be matched to the weapon that fired them.

8. Bullets become scared by rifling as they travel down the barrel of a gun.
This is due to the grooves in that barrel causing the bullet to spin. This spin allows for a true and accurate course upon leaving the barrel.
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9. Striations
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14. Police are able to search the Integrated Ballistics Identification System (IBIS) database to compare markings from bullets, cartridge cases, and shotgun shells to ballistic evidence.

15. Shotguns
Shotguns have a smooth barrel, therefore there are no striations to compare for analysis.

16. What happens when the bullet hits its target?
The results depend on the speed and shape of the bullet and the characteristics of the target.
Most bullets will mushroom
Some will disintegrate

17. Matching Procedure
Analysts use a comparison microscope to compare the striations on the bullet to the grooves in guns to determine the gun that shot the bullet.
Upon collection care must be taken to not harm the striation for correct analysis to occur.

18. Matching Procedure Fire bullets from a suspected weapon
With the aid of a comparison microscope, compare these “test fires” to the suspected bullets
Striations must be identical for a positive match
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