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What is ballistics? Give 3 examples of how ballistics is used
in forensic science.
Introduction Introduction Ballistic evidence helps explain: Ballistic evidence helps explain:
What type of firearm was used. What type of firearm was used.
The caliber of the bullet. The caliber of the bullet.
The number of bullets fired. The number of bullets fired.
Where the shooter was. Where the shooter was.
Whether a weapon was fired recently. Whether a weapon was fired recently.
If a firearm was used in previous crimes. If a firearm was used in previous crimes.
Forensic Science: Fundamentals & Forensic Science: Fundamentals & Investigations, Chapter 17 Investigations, Chapter 17 22
Chapter 17 Chapter 17 Ballistics Ballistics By the end of this chapter you will be able to:By the end of this chapter you will be able to:
describe rifling on a gun barrel and explain how it describe rifling on a gun barrel and explain how it marks a bullet marks a bullet
explain barrel size and caliber explain barrel size and caliber
describe how bullets are test fired and matched describe how bullets are test fired and matched
discuss the role of ballistics recovery and discuss the role of ballistics recovery and examination at a crime scene examination at a crime scene
determine the position of the shooter based on bullet determine the position of the shooter based on bullet trajectory trajectory
Forensic Science: Fundamentals & Forensic Science: Fundamentals & Investigations, Chapter 17 Investigations, Chapter 17 33
All Rights Reserved South-Western / Cengage Learning © 2009
History of Forensic Firearm IdentificationHistory of Forensic Firearm Identification
1835 – London, England. 1835 – London, England. Mold mark used to make Mold mark used to make bullet from molten lead bullet from molten lead used as evidence in used as evidence in homicide casehomicide case
1863 – Examination of 1863 – Examination of the bullet type and design the bullet type and design used to shoot Gen. used to shoot Gen. Stonewall Jackson Stonewall Jackson showed he was shot by showed he was shot by one of his own men one of his own men
1879 – Minnesota. Rifling 1879 – Minnesota. Rifling marks from a revolver marks from a revolver used in court to used in court to differentiate two revolversdifferentiate two revolvers
1925 – The comparison 1925 – The comparison microscope is developed microscope is developed
by Philip Gravelleby Philip Gravelle
Firearm NomenclatureFirearm NomenclatureSlideSlide
BarrelBarrel
ExtractoExtractorrTriggerTrigger
HammerHammer
SafetySafety
AmmunitionAmmunition
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Bullets, Cartridges, and Bullets, Cartridges, and Calibers Calibers
Bullets and cartridges are packaged together. Bullets and cartridges are packaged together.
The bullet, usually of metal, is out front The bullet, usually of metal, is out front with the cartridge, holding the primer and with the cartridge, holding the primer and propellant powders, behind. propellant powders, behind.
Forensic Science: Fundamentals & Forensic Science: Fundamentals & Investigations, Chapter 17 Investigations, Chapter 17 77
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Bullet DesignBullet Design
““Bullet” refers to the projectile(s) which Bullet” refers to the projectile(s) which actually exits the barrel of the gun when actually exits the barrel of the gun when firedfired
Bullets vary in shape and compositionBullets vary in shape and composition
There exist hundreds of different types of There exist hundreds of different types of bulletsbullets
Most types are variations on three main Most types are variations on three main shapes & three basic compositionsshapes & three basic compositions
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Three Main ShapesThree Main Shapes
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Round NoseRound Nose
Maximum penetrationMaximum penetration
Cheapest shape to manufactureCheapest shape to manufacture
Easily loads into chambersEasily loads into chambers
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Hollow PointHollow PointSpreads or mushrooms on impactSpreads or mushrooms on impact
Causes additional damage to targetCauses additional damage to target
Inhibits penetrationInhibits penetration
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Wad CutterWad CutterUsed exclusively as a practice loadUsed exclusively as a practice loadMinimizes penetrationMinimizes penetrationRips a hole in target paper which is visible Rips a hole in target paper which is visible by the shooterby the shooter
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Three Basic Compositions of BulletsThree Basic Compositions of Bullets
LeadLead
½ Jacketed½ Jacketed
Jacketed (Full metal jacket)Jacketed (Full metal jacket) bsapp.combsapp.com
LeadLead
CheapCheap
DenseDense
SoftSoft
Easy to moldEasy to mold
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½ Jacketed½ JacketedA lead bullet coated with copper half way A lead bullet coated with copper half way up the exposed portion of the bulletup the exposed portion of the bullet
Used primarily for Used primarily for hollow pointshollow points
Copper improvesCopper improves exit velocityexit velocity
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JacketedJacketedA lead bullet completely coated in A lead bullet completely coated in coppercopper
Copper improves exit Copper improves exit velocityvelocityUsed to hold the Used to hold the shape of the bullet in shape of the bullet in an effort to maximize an effort to maximize penetrationpenetration
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Caliber of the Cartridge Caliber of the Cartridge Caliber is a measure the diameter of the Caliber is a measure the diameter of the cartridge in hundredths of an inch.cartridge in hundredths of an inch.
Common calibers Common calibers include .22, .25, .357, .38, .44, and .45. include .22, .25, .357, .38, .44, and .45.
Why should the caliber of ammunition Why should the caliber of ammunition match the firearm that shoots it? If they match the firearm that shoots it? If they do not match, what could go wrong? do not match, what could go wrong?
Forensic Science: Fundamentals & Forensic Science: Fundamentals & Investigations, Chapter 17 Investigations, Chapter 17 2020
What happens to bullets when What happens to bullets when theytheyare fired?are fired?
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Pull the Trigger and . . .Pull the Trigger and . . .1.1.A pin or hammer A pin or hammer
strikes the strikes the primerprimer. . This causes a spark.This causes a spark.
2.2.The The powderpowder is then is then ignited causing an ignited causing an explosion.explosion.
3.3.This explosion starts This explosion starts the the bulletbullet down the down the barrel of the gunbarrel of the gun
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Down the BarrelDown the Barrel
4.4.As a bullet As a bullet travels down the travels down the barrel of a gun it barrel of a gun it is twisted by the is twisted by the landslands and and groovesgrooves of the of the barrel.barrel.
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Out of the BarrelOut of the Barrel
5.This 5.This riflingrifling causes the causes the bullet to exit bullet to exit the end of the the end of the barrel in a barrel in a spiral motion.spiral motion.
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Bullet Analysis & Bullet Analysis & ComparisonComparison
What are some What are some characteristics used to characteristics used to
identify & compare bullets?identify & compare bullets?bsapp.combsapp.com
StriationsStriations
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Matching ProcedureMatching Procedure
Fire bullets from a suspected Fire bullets from a suspected weaponweapon
With the aid of a comparison With the aid of a comparison microscope, compare these “test microscope, compare these “test fires” to the suspected bulletsfires” to the suspected bullets
Striations must be identical for a Striations must be identical for a positive match positive match
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ComparisonComparisonMicroscopeMicroscope
Two Two scopes-scopes-
One FieldOne Field
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What happens to a What happens to a bullet when it hits a bullet when it hits a
target? target? •Most bullets tend to Most bullets tend to mushroommushroom when they when they hit a target.hit a target.
•Some bullets nearly Some bullets nearly disintegrate.disintegrate.
•Left are bullet Left are bullet fragments from a ½ fragments from a ½ jacketed hollow point.jacketed hollow point.
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Not all bullets mushroom the Not all bullets mushroom the same. A lot depends on the speed same. A lot depends on the speed and shape of the bullet, and the and shape of the bullet, and the
characteristics of the targetcharacteristics of the target..
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Some more bullets Some more bullets recovered after firingrecovered after firing
The The striationsstriations from the rifling are from the rifling are still visiblestill visible bsapp.combsapp.com
Gunshot Residues Gunshot Residues
Chemical testing often can detect gun shot residue Chemical testing often can detect gun shot residue even if removal is attempted.even if removal is attempted.
What does this mean for investigation?What does this mean for investigation?
Forensic Science: Fundamentals & Forensic Science: Fundamentals & Investigations, Chapter 17 Investigations, Chapter 17 3939
DatabasesDatabases
Like fingerprints, there is a federal Like fingerprints, there is a federal database for firearms used in previous database for firearms used in previous crimes – NIBIN (National Integrated crimes – NIBIN (National Integrated Ballistics Network).Ballistics Network).
Forensic Science: Fundamentals & Forensic Science: Fundamentals & Investigations, Chapter 17 Investigations, Chapter 17 4040
