3/27/2018 1 INDEPTH ANALYSIS OF INTERNAL BALLISTICS 1 C15 Firearms, Tool Marks and Impressions What is Ballistics? •The study of projectiles, trajectories, and the effect on the target What is Firearms Identification? •A sub-discipline of ballistics that determining whether a bullet or cartridge was fired by a particular weapon 2 C15 Firearms, Tool Marks and Impressions ● Forensic Ballistics is divided into three categories: – Internal ballistics – External ballistics – Terminal ballistics THE THREE CATEGORIES OF BALLISTICS 3 C15 Firearms, Tool Marks and Impressions A Internal ballistics What happens in the weapon B External ballistics What happens after the bullet leaves the barrel C Terminal ballistics (wound ballistics) What happens when the bullet hits the target DESCRIPTION OF THE THREE CATEGORIES OF BALLISTICS Change Your Life * 4 C15 Firearms, Tool Marks and Impressions WHAT’S A CARTRIDGE? A cartridge (also called a round or a shell) is a type of ammunition ) which is is a combination of: bullet casing bullet (projectile) propellant ) (usually either smokeless powder) primer All of which is precisely made to fit within the firing chamber of a firearm . Change Your Life * 5 C15 Firearms, Tool Marks and Impressions Cartridges Design The bullet, usually made of metal, is out front with the cartridge, holding the primer and propellant powders, behind. Change Your Life * 6 C15 Firearms, Tool Marks and Impressions
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INDEPTH ANALYSIS OF INTERNAL BALLISTICS•A sub-discipline of ballistics that determining whether a bullet or cartridge was fired by a particular weapon 2 C15 Firearms, Tool Marks
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3/27/2018
1
INDEPTH ANALYSIS OF INTERNAL BALLISTICS
1C15 Firearms, Tool Marks and
Impressions
What is Ballistics?•The study of projectiles, trajectories, and
the effect on the target
What is Firearms Identification?
•A sub-discipline of ballistics that determining whether a bullet or cartridge was fired by a particular weapon
2C15 Firearms, Tool Marks and
Impressions
● Forensic Ballistics is divided into three categories:
– Internal ballistics
– External ballistics
– Terminal ballistics
THE THREE CATEGORIES OF BALLISTICS
3C15 Firearms, Tool Marks and
Impressions
A Internal ballistics
What happens in the weaponB External ballistics
What happens after the bullet leaves the barrelC Terminal ballistics (wound ballistics)
What happens when the bullet hits the target
DESCRIPTION OF THE THREE CATEGORIES OF BALLISTICS
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4C15 Firearms, Tool Marks and
Impressions
WHAT’S A CARTRIDGE?A cartridge (also called a round or a shell) is a type of ammunition) which is is a combination of:
bullet casingbullet (projectile)propellant) (usually either smokeless powder) primer
All of which is precisely made to fit within the firing chamberof a firearm.
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5C15 Firearms, Tool Marks and
Impressions
Cartridges Design
The bullet, usually made of metal, is out front with the cartridge, holding the primer and propellant powders, behind.
As a result of rifling, a barrel will impress a negative impression of itself on the sides of the bullet
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13C15 Firearms, Tool Marks and
Impressions
Matching
impressions
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14C15 Firearms, Tool Marks and
Impressions
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15C15 Firearms, Tool Marks and
Impressions
A Fired bullet: Class evidence
•Different gun manufacturers use different rifling techniques. These techniques impart the class characteristics on a fired bullet.• Number of impressions
• Width of impressions
• Depth of impressions
• Angle of impressions
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16C15 Firearms, Tool Marks and
Impressions
Q: How are these 2 guns different
A: caliber
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17C15 Firearms, Tool Marks and
Impressions
What is caliber?
• Caliber = the diameter of the bullet.
• Measured in hundredths of an inches.• .22, .357, or .50
• Measured in metrics• 9mm
Question: Why should the caliber of ammunition match the firearm that shoots it? If they do not match, what could go wrong?
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18C15 Firearms, Tool Marks and
Impressions
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Showing variation within caliber
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19C15 Firearms, Tool Marks and
Impressions
Striations on bullets are not the only features used in firearm investigations.
• BREECH MARKS PLAY A VITAL ROLE IN DETERMINING IF A CERTAIN BULLET WAS FIRED FROM A FIREARM.
• BREECH MARKS ARE FOUND ON THE REAR OF A FIRED CARTRIDGE
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20C15 Firearms, Tool Marks and
Impressions
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21C15 Firearms, Tool Marks and
Impressions
A
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22C15 Firearms, Tool Marks and
Impressions
• When a bullet is fired, the explosion forces:
1. the bullet down barrel
2. the cartridge back against breech
– Leaving a negative impression on the back of the cartridge
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23C15 Firearms, Tool Marks and
Impressions
Depending on the make of gun & normal wear and tear, the breech markings will pick up class, and hopefully, individual characteristics.
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24C15 Firearms, Tool Marks and
Impressions
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Examples of breech markings
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25C15 Firearms, Tool Marks and
Impressions
Shot Gun vs. Handgun
• Shotguns have smooth barrels with no rifling.
• Are there lands or groves on the bullet(s)?
• How can a F.S. identify trace evidence left by a shotgun?
• Only by marks on the spent shell casing(s):
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26C15 Firearms, Tool Marks and
Impressions
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27C15 Firearms, Tool Marks and
Impressions
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28C15 Firearms, Tool Marks and
Impressions
Shotgun into ballistics gel
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29C15 Firearms, Tool Marks and
Impressions
How CSI determines if a recovered bullet from a crime scene came from a suspected gun