Ballistics:

Study of projectiles in motion

Look for direction of travel, entrance and

exit. Determine Muzzle to first surface distance

3 Areas of Ballistics:

Interior Ballistics - The study of projectiles within the firearm (during barrel travel)

Exterior Ballistics - The study of projectiles in flight (after the barrel)

Terminal Ballistics - The study of a projectile’s interaction with a target ú Wound Ballistics - A sub-set of terminal ballistics

dealing with the human body as the “target”

Common  Issues  in  Shooting  Incidences

The range from which a firearm was discharged The position of a firearm at the moment of

discharge The location of a victim at the moment of the

projectile impact The number of shots fired in a multiple discharge

incident The sequence of shots fired in a multiple discharge

incident The presence and nature of any intervening material

between the firearm and the victim

3

Trajectory

Trajectory: The arched path that a bullet follows through flight Perforate: To pass all the way through Penetrate: To enter and stay in § Where was the shooter located? § Path taken by the propelled bullet.

Trajectory and Gravity

§ A fired bullet has 2 forces acting on it

ú Forward force from gunpowder

ú Downward force of gravity

Bullet:

1. Begins to drop as it leaves the barrel

2. Therefore shooter must make adjustments

for distance in line of sight.

3. Wind Speed and direction must be

accounted for

Entrance & Exit Wounds§ Position body as it was

§ Use dowels, string or lasers to

determine shooter position

over 28,000 deaths in the US annually due to shootings

The Physics of penetrating traumaKinetic Energy

Greater the mass the greater the energy

Greater the speed the greater the energy

Small fast bullets can cause more damage than large and slow bullets

KE = mass (weight) x velocity (speed)2 2

Tissue damage as a result of GSW

Depends on the bullet and the energy behind its force (size of the gun)

Distance from the body

Location & trajectory/path of injury

Permanent versus temporary cavity

Permanent and Temporary Cavitation

Cavitation: The radial dispersion of energy created by the projectile

Permanent: tissue crush and excavation

Temporary: Blast effect due to tissue stretch

Bullet Fragmentation

Causes the most damage to the tissue

Damage PathwayDirect Injury

Damage done as the projectile strikes tissue

Pressure Shock Wave Human tissue semi-fluid Solid and dense organs

damaged greatly Temporary Cavity

Due to cavitation Permanent Cavity

Due to seriously damaged tissue

Zone of Injury Area that extends beyond

the area of permanent injury

Projectile Fired

Tip of Projectilestrikes tissue

Tissues pushedforward and away

Tissues collide

Rapidcompression,

crushes and tearstissue

Shock waveis created

Cavity formsbehind bullet

pulling debris intowound

Bullet fragments Bullet becomesdeformed

Specific Tissue and Organ Injuries

Connective Tissue   Absorbs energy and limits tissue

damage Organs

  Solid organs ú Dense and low resilience

  Hollow organs ú Fluid filled: transmit energy = increased

damage ú Air filled: absorb energy = less damage

General Body Regions

Extremities Injury limited to resiliency of tissue 60–80% of injuries with

General Body Regions Neck

Damages trachea and blood vessels Neurological problems Sucking neck wound

Head Cavitational energy trapped inside skull Serious bleeding, lethal

Determining the Location of the Shooter

Building is 60 feet away along the horizon line

Bullet hole is 4 feet above ground

Where is the shooter located?

How to Read a Right triangle

• Sine, Cosine and Tangent are all based on a Right-Angled Triangle

SOH-CAH-TOA

sine = opposite/hypotenuse

Cosine = adjacent/hypotenuse

Tangent = opposite/adjacent

“opposite” is opposite to the angle

“adjacent” is adjacent (next to) the angle

“Hypotenuse” is the long one

Calculating Impact Angle

Measure the elliptical shape of the bullet hole and use trig to calculate angle of impact.

Sine (i) = minor/major

Trig calculation of impact angle:

sin = w/l 9mm/18mm = 0.50

Arcsine of 0.50 = 30 degrees

major

minor

Example: find the height of side d

Start with:sin 39 = opp/hyp

d/39

Swap Sides d/30 = sin 39

Find the sin 39 degrees

d/30 = 0.629

Multiply both sides by 30

d = 0.629 x 30 d = 18.88