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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