Firearms, Ammunition, Ballistics, Gunshot Wounds

Honors Forensics Science

What are the five types of small arms?

Handguns

Rifles

Shotguns

Submachine guns

Machine guns

Handguns

Single Shot Pistol

One firing chamber and barrel, manually loaded

Handguns

Derringer

Single shot pistol with 2 barrels, individually loaded

Handguns

Revolver

Revolving cylinder mechanically rotated

What’s the most common handgun in the United States?

Revolver

Handguns

Auto-loading pistols (automatic)

bullets are stored in a clip, each time trigger is pulled a projectile is released

What are Rifles?

Firearms with a rifled barrel designed to be fired from the shoulder

What are the five categories of rifles?

Single-shot

Lever-action

Bolt-action

Pump-action

Auto-loading

Assault Rifle (AR)

Autoloading

20 or more rounds in magazine

Fully automatic firing

fires intermediate rifle cartridge

Shotguns

Firearms shot from shoulder with minimum of 18-inch non-rifle barrel; shoots many projectiles

What are the seven types of shotguns?

single-shot

over-under

double-barrel

bolt-action

lever-action

pump-action

auto-loading

Submachine guns / Machine pistols

fired from shoulder or hip

fully automatic firing

rifled barrel

fires pistol ammunition

Machine Guns

Fully automatic

Fire rifle ammunition

Ammunition - Small Arms

Cartliage Case

Primer

Propellant

Projectile

What are bullets?

The part of cartilage that leaves the muzzle

What are the four types of bullets?

Round Nose

Semi-wad cutter

Hollow point

Wad cutter

Primors:

• Contain a compound that ignites when struck by the firing pin

• Force is driven through the falsh hole and ignites the gun powder

- Rim Fire

- Center Fire

Rifling Definition

Sprial grooves cut the length of the barrel; makes bullet spin, improving distance and accuracy

Rifling Lands

The raised part

Rifling Grooves

Rifling can have:

right had or left had twist

Rifling allows for:

analysis/comparison

Mechanism of firing a projectile

Pull tigger → cause firing pin to strike primer →primer ignites, releases through the flash hole, and ignites the gun powder →explosion of gun powder creates force → force can only release down the barrel, causing projectile to travel down the barrel →rifle creates spin on bullet as it leaves the barrel

Yaw

The horizantal rotation of an bullet as it travels forward, rocking motion

Caused by firing

(think of a footbal)

Class and Individual Characteristics of Bullets

• Number of lands and grooves

• Diameter of lands and grooves

• Width of lands and grooves

• Depth of grooves

• Direction of twist

• Degree of twist

Catridge Case Analysis

Rimfire vs Centerfire

Magazine markings

Ejector marks

Size, shape

Wound Ballistics

K.E. = Kinetic Energy = WV²/2gravity

Double weight = double energy

Double velocity = quadruple energy

What are the 4 factors the affect loss of K.E.?

• K.E. of bullet at time of impact

• Angle of yaw at time of impact

• Calider, construction, configuration of bullet

• Density, strength, and elasticity of tissue struck by bullet

What are the four classifications of gunshot wounds?

• Contact wounds

• Near-contact wounds

• Intermediate-range wounds

• Distant wounds

Contact Wounds

Muzzle is pressed against surface of body

• Hard contact

• Loose contact

• Angle contact

• Incomplete contact

• Near contact

Hard contact

• Muzzle pressed hard against skin at time of discharge; skin envelops the tip of the barrel

• Edges of entrance are scarred and blackened

• Soot is embeded; cannot be removed

Loose Contact

• Muzzle held loosely against skin

• when gun is fired, small gap is created by the force, allowing some gas to escape

• soot is deposited in a zone; can be wiped away

Angled Contact

• Muzzle held at an angle; not in contact with skin

• Gas and soot escape

• Entrance wound is present at base of scarred zone

• Majority of soot in opposite side of wounds; points away from muzzle

Incomplete contact

Variation of Angled contact gap in between weapon and skin

Most often seen in self-inflicted gun shot wounds

Near Contact

Gun is almost in contact with skin, but still very close

Sear marks and blackened soot

Stippling

Multiple Punctate abrasions of the skin due to impact from small foreign fragments

Powder tattooing

like stippling, but if small foreign fragments is gunpowder (fired from close distance)

Stippling and Powder Tattoing

Different from powder burns

Only happen to people alive at time of shooting

What is the most common non powder stippling?

Glass

Intermediate-Range wounds

• Gun is not touching the skin, but close enough for powder tattooing/ soot

• starts at 10mm with handguns

What 7 things determine the intensity of soot patterns in Intermediate-range wounds?

• Range

• Propellant

• Angle of Muzzle

• Barrel length

• Caliber

• Type of weapon

• Target material

Distant Gunshot Wounsd

Only marks on target are produced by the action of the bullet

Entrance Wounds

• Abrasion ring →redish/redish brown ring of abraded epidermis surroudning entrance hole

• Moist and fleshy in appearance

• Skin “rubbed raw”

Perforate

means bullet enters and exits

Penetrate

Bullet enters only

Entrance Wounds

Graze

Bullet strikes at shallow angle without perforating skin

Entrance Wounds

Tangential

Laceration of subcutaneous tissue (fat)

Entrance Wounds

Superficial Perforating

Shallow, “through and through.”

Entrance and exit wounds are close together

Entrance Wounds

Re-entry

Bullet passes through one part of body and into another

Entrance Wounds

Shoring of entrance wound

seen in second entrance of re-entry when two body parts are touching

Exit wounds

• typically larger and more irregular than entrance wounds

• Slit, crescent, circular, stellate, shored, or irregular

Shored Exit Wound

Skin at exit point pressed against hard surface (like chair or floor)

Intermediate-Distant Wounds of Skull

Skull will have bevilling on the impact side and exit (more severe on exit side)

Skull Wounds

• Tangential wounds are “gutter wounds,” damaging skull and forcing fragments into brain

• Low angle bullets have a “keyhole,” with one side looking like an exit and the other looking like an entrance

Contact-Wounds of Skull

• Pressure build up of gas from the muzzle to the skull causes skin to rip apart in an stellate (star) pattern; can also be caused by high powered rifle

Backspatter

ejection of blood and tissue from a gunshot entrance wound