Forensic Ballistics

Forensic Ballistics

What is Ballistics?

• Ballistics: the study of bullets and firearms

• Firearm: a weapon capable of firing projectiles using a confined explosive

  • Includes guns, canons

  • Does not include blow darts or bows and arrows

History of Ballistics

• Gunpowder was first created in China in the 2nd Century

  • Made of Potassium Nitrate, Charcoal, and sulfur

    • Expands and explodes when ignited

  • Originally used to make fireworks and small canons

History of Ballistics

• 14th century Europe: inventors create the first guns by shrinking the cannon cylinder down

  • Earliest guns were matchlocks and had wicks like a candle

  • Overtime flintlock weapons were created

    • Could be used in wet weather

• Early guns were muzzle loaders that needed the gunpowder and projectile to be placed down the barrel

• Eventually, modern percussive firing replaced flintlocks

Multiple Choice

Which of the following is not an ingredient in gunpowder?

• charcoal

• Potassium Nitrate

• Sodium Chlorate

• Sulfur

Multiple Select

Select all the weapons that could be considered a firearm

• cannon

• rifle

• bow and arrow

• spear

• pistol

Multiple Choice

Which type of weapon was created first?

• Flintlocks

• Matchlocks

• Muzzle Loaders

• Percussive firing weapons

Multiple Choice

What is the major advantage of flintlock weapons over matchlock weapons?

• They are lighter

• They are easier to aim

• They can carry more bullets at a time

• They can be used in the rain

Parts of the gun

• Bullet: The projectile fired from a gun

• Cartridge: a case that holds a bullet, primer powder, and gunpowder

• Breech: end of the gun opposite the barrel, where cartridges are loaded

Types of Guns

• Long Guns: Need two hands for firing

  • Rifles shoot bullets

  • Shotguns shoot slugs or pellets

Types of Guns

• Handguns/Pistols: can be fired with one hand

  • Revolvers: Bullets are loaded in a cylinder that can be turned

    • The cartridge has to be manually moved after each shot

  • Semiautomatic: Hold multiple bullets in a clip but only fire once per trigger pull

  • Fully Automatic: Bullets fire as long as the trigger has pressure on it

Multiple Choice

Semiautomatic pistols store cartridges in a

• clip

• cylinder

• firing pin

• muzzle

Multiple Choice

Shotguns are examples of

• handguns

• long guns

• revolvers

• semiautomatic weapons

Multiple Choice

Which type of handgun do you physically have to move the bullets by spinning a cylinder

• Rifles

• Revolvers

• Fully automatic weapons

• Shot guns

Anatomy of a Cartridge

• Bullets are housed inside a case that holds the different components together

  • Can be made of lead, copper, or a metal alloy

• Primer Powder: a mixture that starts the explosion that pushes the bullet down the chamber

  • delivered to the gunpowder by the anvil and flash hole

• Headstamp: an engraving on the bottom of the cartridge that identifies the caliber and manufacturer

What is Caliber?

• Caliber: the measure of the diameter of the cartridge

  • usually measured in hundredths of an inch, but European bullets are measured using the metric system

Multiple Choice

Which of the following is not part of the cartridge?

• barrel

• bullet

• gunpowder

• primer powder

Multiple Choice

What part of the bullet tells you the maker of a bullet

• The Cartridge

• The Hammer

• The Case

• The Headstamp

Multiple Choice

True or False: Caliber is always measured in hundredths of an inch

• True

• False

Ballistic Markings

• Grooves inside of a gun barrel helps the bullet to fly straight

  • Lands: The raised areas that surround grooves in a gun

• As the bullet leaves the barrel, the heat causes the grooves to leave indentations in the metal

Ballistic Markings Accuracy

• In some cases, it is possible to match a bullet to a gun, but this is not as accurate as shown in fiction

  • Every bullet is different and can have flaws that mix with the rifling pattern

  • There is no real standard for how to compare a bullet to the chamber of a gun

  • The more a gun is fired, the more friction inside of the barrel that can slowly change the rifling pattern over time

• Despite many of the flaws with Ballistic Markings, it is still used as critical evidence in many cases

Gunshot Residue (GSR)

• When a gun fires, gun powder explodes and sends particles of gunshot residue into the air

• This residue can land on the person holding the gun and the surrounding area

• GSR can be somewhat washed away, but still leave chemical traces behind

  • These traces can indicate a false positive is someone uses a firearm

• GSR is often used to determine the distance between the victim and the weapon

Trajectory

• Trajectory: the path of a propelled bullet, used to trace back to the point where the weaponed was fired from

• Need two reference points to calculate

  • An entrance and exit wound can do this

Trajectory

• Bullets usually travel in a straight line horizontally but can be deflected in some situation

• When the bullet leaves the gun, gravity pulls it downwards

  • The farther from the target, the more of an arc there is

Multiple Choice

True or false: The lands and grooves of a barrel's rifling improve the accuracy of a bullet

• True

• False

Multiple Select

Which of the following factors can affect the accuracy of ballistic markings?

• flaws in the bullet casing

• A lack of consistent standards for comparisons

• Gun barrels can wear down over time

• A casing might not get marked if it is wet

• A criminal can coat a bullet with oil to interfere with the markings

Multiple Choice

Which of the following best describes the trajectory of a projectile?

• The height of the shooter

• The path a bullet travels

• the housing for the bullet’s gunpowder

• the pattern of lands and grooves on the projectile