firearms

ballistics

study of projectiles in flight

class evidence

caliber size, type of firearm, name of manufactuer

individual evidence

markings on projectiles and cartridge casings that are unique

trajectory

the flight path of a projectile

parabolic path

trajectory of any propelled object

Newtons third law of motion

“For every action, there is an equal and opposite reaction”

discharging a firearm

forward propulsion (action) and backward force (recoil)

long guns

rifiles and shotguns; barrel of shotgun is smooth, grooves inside rifile

rifiles

Grooves (indentations) in the barrel

Lands (ridges) surround the grooves

handguns

pistols and revolvers

primer

located at the bottom of the cartridge and contains primer powder; only area producing gunshot residue

wad

plastic or paper that creates a seal to stop the explosive gases from blowing by shot

shot

many round pellets

slug

single projectile

bullet

rounded or pointed projectile; fired from a firearm located at the front of the carriage

cartridge

casing that contains the bullet, gunpowder and primer powder

headstamp

Located at the bottom of the cartridge at the opposite end of the bullet. The size (caliber) and the manufacturer of the cartridge are stamped on the headstamp

caliber

Bullets are classified by caliber and length

The caliber is the measure of the diameter of the bullet

.22 caliber is 22/100’s of an inch

The European method of naming firearm caliber uses the metric system for measuring the bullets diameter

Caliber also refers to the diameter of the inside of a firearms barrel because the bullet moves through the barrel the caliber should match the firearm

gunshot wound mechanics

• The .223 cartridge vs .22 cartridge

  • Significantly more powder

  • A much heavier bullet

  • Travelling at a higher velocity

  • Different design - sharp point

  • This means that the .223 bullet jas much more energy to deliver its target

Rifled barrels

The rifling pattern left on the bullet it's different and specific to each firearm

It is impossible to produce two identical rifled barrels

Analysis of firearm and ballistics

Type, manufacturer, caliber

Rifling pattern

Serial number

individualized wear and tear

test-firing

The projectiles are fired through a tank of water, ballistic soap or gel

The recover projectiles are examined to determine the unique land and groove pattern

A comparison is made between the test fired bullets and the weapons recovered from the crime scene

NIBINS

NIBINS is an automated and shared database of firearm evidence submitted by local, state, and federal law enforcement agencies

The purpose of NIBINS is to quickly capture and compare firearm evidence from all over the country to determine whether the firearm under examination was used in a previous crime

internal ballistics

firearm examiners; ejection patterns, gunshot reisdue patterns, shotgun shot patterns, examination of bullets and fragments for damage

layering of trace

indicative of sequencing

damage

indicative of what the projectile struck

deformation

indicative of deflection along flight path

distance of spray pattern

the wider the spray pattern, the further the distance between the shooter and the victim

ejection patterns

Right and slightly back

Kinda indicate where the shooter was; Surface, Rolling, Disturbed

residue patterns

Range to target to determination

Surface determination

Specific weapon and ammunition

The closer you are to the subject, the more debri you will have

gunshot residue

When a firearm is discharged, gases from the primer and burning gunpowder vaporize and then condense into particles. These particles escape from the barrel and cylinder

blowback

Some of the gases that escape are deposited to the rear and the GSR particles may land on the shooter's hand

analysis of gunshot residue

Soot and unburned powder

Nitrates from the primer

Detected on hands or clothing

May be deposited on victim

firearms

composition of primer particles: lead, barium, antimony
will only show if gun has been fired

GSR disadvantages

gears can be washed off, gsr can be transferred from person to person, usually only travel up to 48 inches

terminal ballistics

pathologists consider the effects the projectiles have on the body; type of wounds, entry or exit, wound path

penetrating

enters but does not exist

perforating

enters and exists

ricochet

deflects at some angle with no penetration

tangential

skims along a surface

close contact

direct contact with skin; most of the soot, burned and unburned particles end up inside the wound; skin is burned

loose contact

small gap between skin and muzzle; soot and particles appear in and around the wound. explosion of hot gases separate layers of skin and cause a radial or star-shaped pattern

near contact

muzzle not more than 5 inches from skin

intermediate range

generally between 5-40 inches from skin; presence of stippling around skin (looks like freckles)

indeterminate

no determination of distance; no markings, no strippling, greater than 30 inches

shooting reconstruction

The locations of the individuals involved in the shooting incident.

Location of objects in the projectile's path

Sequence of shots fired at the scene (windshield glass / fracture patterns)

methods used in shooting reconstruction

string/dowel rods, laser, trigonometry, scaled drawings, computers
height of gun is estimated at 48”, 54”, and 60”
The exact height of the muzzle of the gun will never be known but can only be assumed due to the height and orientation of the shooter