1. What is ballistics? Give 3 examples of how ballistics is used in forensic science.

2. Forensic Science: Fundamentals & Investigations, Chapter 17
Introduction
Ballistic evidence helps explain:
What type of firearm was used.
The caliber of the bullet.
The number of bullets fired.
Where the shooter was.
Whether a weapon was fired recently.
If a firearm was used in previous crimes.
Forensic Science: Fundamentals & Investigations, Chapter 17

3. History of Forensic Firearm Identification
1835 – London, England. Mold mark used to make bullet from molten lead used as evidence in homicide case
1863 – Examination of the bullet type and design used to shoot Gen. Stonewall Jackson showed he was shot by one of his own men
1879 – Minnesota. Rifling marks from a revolver used in court to differentiate two revolvers
1925 – The comparison microscope is developed by Philip Gravelle
Please refer to the document titled “History of Firearm Identification” by Dr. James Hamby included on the disk for more information and discussion topics.

4. Firearm Nomenclature Slide Barrel Extractor Trigger Hammer Safety
We first need to discuss the various parts of a firearm to understand the functioning of a firearm. The slide of a semiautomatic firearm is used to load the firearm. In order to fire a semiautomatic pistol, the ammunition is loaded in a magazine and placed in the grip. The slide is then pulled to the rear under spring tension. On its’ forward return the slide strips a cartridge from the magazine into the barrel of the firearm. The firearm is now ready to fire.

5. Ammunition
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6. Caliber of the Cartridge
Caliber is a measure the diameter of the cartridge in hundredths of an inch.
Common calibers include .22, .25, .357, .38, .44, and .45.
Why should the caliber of ammunition match the firearm that shoots it? If they do not match, what could go wrong?
If they don’t match – the bullet could get stuck or possibly cause the gun to explode/get extremely hot/backfire.
Forensic Science: Fundamentals & Investigations, Chapter 17

7. Forensic Science: Fundamentals & Investigations, Chapter 17
Bore
Interior diameter of a gun barrel
Forensic Science: Fundamentals & Investigations, Chapter 17

8. Bullets, Cartridges, and Calibers
Bullets and cartridges are packaged together. The bullet, usually of metal, is out front with the cartridge, holding the primer and propellant powders, behind.
Forensic Science: Fundamentals & Investigations, Chapter 17

9. Forensic Science: Fundamentals & Investigations, Chapter 17
Shotgun Ammunition
Gauge- interior diameter of a shotgun barrel as determined by the number of lead balls of a size fitting in the barrel
Shot- lead spheres in a shotgun shell
Slug- single pellet or sphere
Forensic Science: Fundamentals & Investigations, Chapter 17

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13. Bullet Design
“Bullet” refers to the projectile(s) which actually exits the barrel of the gun when fired
Bullets vary in shape and composition
There exist hundreds of different types of bullets
Most types are variations on three main shapes & three basic compositions
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14. Three Main Shapes
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15. Round Nose Maximum penetration Cheapest shape to manufacture
Easily loads into chambers
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16. Hollow Point Spreads or mushrooms on impact
Causes additional damage to target
Inhibits penetration
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17. Wad Cutter Used exclusively as a practice load Minimizes penetration
Rips a hole in target paper which is visible by the shooter
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18. Three Basic Compositions of Bullets
Lead
½ Jacketed
Jacketed (Full metal jacket)
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19. Lead
Cheap
Dense
Soft
Easy to mold
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20. ½ Jacketed
A lead bullet coated with copper half way up the exposed portion of the bullet
Used primarily for
hollow points
Copper improves
exit velocity
Lead promotes mushrooming
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21. Jacketed A lead bullet completely coated in copper
Copper improves exit velocity
Used to hold the shape of the bullet in an effort to maximize penetration
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22. What happens to bullets when they are fired?
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23. Pull the Trigger and . . .
A pin or hammer strikes the primer. This causes a spark.
The powder is then ignited causing an explosion.
This explosion starts the bullet down the barrel of the gun
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24. Down the Barrel
As a bullet travels down the barrel of a gun it is twisted by the lands and grooves of the barrel.
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25. Out of the Barrel
5.This rifling causes the bullet to exit the end of the barrel in a spiral motion.
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26. Bullet Analysis & Comparison What are some characteristics used to identify & compare bullets?
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27. Striations
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32. Forensic Science: Fundamentals & Investigations, Chapter 17
Striae/cannelures
Parallel sets of scratches on a bullet caused by unique markings in the bore of a rifled weapon (like fingerprint)
Can be hard to see if badly deformed pg. 445
Cannelures- groves on bullet that help secure it to the cartridge casing
Forensic Science: Fundamentals & Investigations, Chapter 17

33. Forensic Science: Fundamentals & Investigations, Chapter 17
Cartridge
Consists of bullet and case (with powder)
Can be both class & individual evidence
Head stamp- numbers or letters found at base of cartridge (show caliber, code & manufacturer)
Forensic Science: Fundamentals & Investigations, Chapter 17

34. Breech Marks Portion of gun that contains firing mechanism
Can have marks on them after cartridge is slammed backward after being fired
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35. What happens to the cartridge after firing the firearm?
Extractor- hooked type part that withdraws the casing from the chamber after firing
Ejector- part that throws out casing after gun is fired
Forensic Science: Fundamentals & Investigations, Chapter 17

36. Some scratches may not be from firing
Can happen because of movement before firing
Can happen in magazine or chamber
Magazine (clip)- container that holds cartridges under pressure to be fed into chamber
Chamber- holds cartridge for firing
Forensic Science: Fundamentals & Investigations, Chapter 17

37. Forensic Science: Fundamentals & Investigations, Chapter 17
Review
Modern ammunition consists of what four many parts?
Explain how bullet are sized differently in handguns and rifles as opposed to shotguns?
What are the three main bullet types?
What is on the back of the cartridge that shoes the manufacturer, caliber, & size?
What part of an unfired bullet helps to keep the cartridge case attached to the bullet?
Why do you think breech marks are important to forensics?
Forensic Science: Fundamentals & Investigations, Chapter 17

38. Comparison Microscope
Two scopes- One Field
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41. What happens to a bullet when it hits a target?
Most bullets tend to mushroom when they hit a target.
Some bullets nearly disintegrate.
Left are bullet fragments from a ½ jacketed hollow point.
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42. Not all bullets mushroom the same
Not all bullets mushroom the same. A lot depends on the speed and shape of the bullet, and the characteristics of the target.
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44. Some more bullets recovered after firing
The striations from the rifling are still visible
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45. Forensic Science: Fundamentals & Investigations, Chapter 17
Gunshot Residues
Chemical testing often can detect gun shot residue even if removal is attempted.
What does this mean for investigation?
Forensic Science: Fundamentals & Investigations, Chapter 17

46. Forensic Science: Fundamentals & Investigations, Chapter 17
Databases
Like fingerprints, there is a federal database for firearms used in previous crimes – NIBIN (National Integrated Ballistics Network).
Forensic Science: Fundamentals & Investigations, Chapter 17