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Firearms and Ballistics

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Ashleigh Litvin

on 12 February 2018

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Transcript of Firearms and Ballistics

Firearms and Ballistics
Ballistics Evidence
Firearm
-- a portable gun, capable of firing a projectile using a confined explosive
Ballistics
-- the study of a firearm projectile in flight

Ballistics evidence provides clues; helps police answer many questions pertaining to a crime scene.

What type of firearm was used?
What was the caliber of the bullet?
How many bullets were fired?
Where was the shooter standing?
What was the angle of the impact?
Has the firearm been used in a previous crime?
History of Gunpowder and Firearms
A percussion-cap firearm ignites the gunpowder using a primer that explodes when struck by a small hammer.
Matchlock Firearm
Conclusion
Suicide or Homicide?
March 2000 -- Sandra Dyust's body was found lying on blood-spattered sheets next to a 9-millimeter pistol.
Originally thought suicide, but during the autopsy one entrance wound and two exit wounds were discovered.
Firearms and Rifling
The principle of spinning the projectile is part of the design of "rifled guns," or rifles.

Within the gun's barrel, grooves and lands cause a bullet to spin when exiting the barrel of the gun (ex: football spirals)
Grooves: the indentations in the rifle's barrel.
Lands: The ridges that surround the grooves

The rifling pattern left on the bullet by the lands and grooves is unique to the firearm.

Comparison microscope - used compare the patterns of lands and grooves in pistols and rifles (provides valuable evidence).
*1475* - matchlock firearms (earliest firearm)
*Early 1600s* - matchlock replaced by flintlock firearms
Flintlocks were muzzle-loaders
Fired round projectiles made of lead
*1820* - flintlock replaced by percussion-cap firearms
introduction of the
cartridge
, a case that holds a
bullet
(a pointed projectile), gunpowder, and small amount of primer powder
Cartridges were loaded into the gun from the opposite end of the barrel - the
breech.
Case Study Continued
Sandra's note to her sister..."If anything has happened to me, look first to David Dyust, Sr."

Blood evidence at the crime scene included a void consistent with someone standing over the victim.

Tiny blood spots consistent with a mist of blood produced by a high-velocity, close-range impact were found on David's shirt. DNA testing confirmed the blood was Sandra's.
Semiautomatic Weapons
Fire only one bullet per pull of the trigger
Carry cartridges in a magazine which is locked into the grip of the firearm
Handguns can be classified as revolvers or semiautomatic firearms

Fully Automatic Weapons
Fire repeatedly as long as the trigger is pressed

In both, the empty cartridge is ejected, and the next cartridge is loaded automatically.
Who invented gunpowder?

What is gunpowder made out of? Gunpowder (black powder) consists of potassium nitrate, charcoal, and sulfur.

14th-century Europe, inventors learned they could direct the explosive force of gunpowder down a cylinder to move a deadly projectile.

For a firearm to work reliably, it must ignite the gunpowder.
Long Guns and Handguns

Long guns (rifles and shotguns) require the use of two hands
Rifles
fire bullets, whereas shotguns can fire either a shot or a slug.
The longer the barrel on a firearm, the greater the accuracy
Handguns: intended to be fired with one hand, are called pistols
Samuel Colt (1835) - developed and patented the
revolver
; cylinder that held the cartridges turned as it fired.
Bullets and Cartridges
A bullet is a projectile propelled from a firearm.
It can be composed of lead or combinations of various metals.

The cartridge includes primer powder, gunpowder, the bullet, and the casing material that holds them all together.
Classified as rimfire or centerfire
Area where the firing pin strikes the cartridge casing (on the rear of cartridge)
The headstamp on the bottom of the cartridge casing identifies the caliber (size) and manufacturer. The headstamp is on the bottom of the cartridge casing.
1. Ballistics is the study of?
2. Name the three early firearms
3. Modern firearms are divided into two basic types, which are?
4. Handguns can be classified as revolvers or ____?
5. Bullets fired from a firearm show patterns of _____ and ____ ?
6. A cartridge consists of?
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