Forensics Ballistics

firearms

Ballistics

study of projectiles, trajectories and effect on the target

Ballistic evidence determains…

• the type of firearm, caliber of bullet, number of bullets fired, where the shooter was

Caliber

the diameter of gun barrel/bore/bullet measured between opposite lands

Lands

rasied portions between the groves recessed portions inside the barrel

Grooves

the spiraled, recessed channels cut into the inside of a rifle barrel

Rifling

produces twisting that adds accuracy and individualized pattern on a bullet

Each marking is…

individual to each gun

the anatomy of ammunition includes

-projectile

-propellant/explosive

-primer

-casing/cartridge

IBIS

Integrated Ballistic Identification System

-uses digital microscopic images

Comparison Microscope

if both bullets (from crime scene and one being tested) have same class characterstic when placed under comparison microscope

- single most important tool for firearm exaimination

for every action…

there is a equal and opposite reaction

physics of recoil

Bullet travels forward, case is forced backwards against the breechblock, causing recoil

• In an automatic or semi automatic weapon, this recoil is what drives the action to “cycle”

pulling the trigger…

Releases weapon’s firing pin causing it to strike the primer which ignites the powder - Expanding gases generated by burning gunpowder propel bullet forward through the barrel

gunshot residue

Particles of unburned powder and traces of smoke

GSR can leave traces on…

the hand, arm, face, hair, victim, or clothing of the shooter 

Griess test for GSR

1. Use swab of cotton with 5% nitric acid

2. Front and back of each hand swabbed separately 

3. Obtain a 5th control area (under shirt or protected area)

These Two major forces are acting on a bullet once it is fired

gravity and trajectory

Trajectory

the path a projectile, like a bullet, follows after being fired

(Two reference points are needed to define the trajectory)

how to solve for tan/trajectory

1. tan of degrees (opp over adjecent)

2. multiply by distance from building

3. add height above horizon

4. divide by 10 for each floor

when a bullet hits a surface at a 90 degree angle (straight on)

the hole is round

the smaller the angle…

the longer the hole will be

the breech

The end of the barrell attached to the firing mechanism of a firearm where the cartridge is loaded and unloaded

the job of the firearms examiner involves examining:

used bullets and their spent casings for telltale markings left on them by a specific firearm.

entry wounds are…

inverted, start and stay small

exit wounds are…

everted, raggered flaps, start small gets big

start of csi episode

While having breakfast at a diner, a truck crashes through the establishment, and a group of armed men storm in. They fatally shoot Angell and abduct Connor, fleeing the scene in a Hummer

jesses shooter was using a

50 calliber hallow wood

what method is used to find where shooter was standing?

lasers

what bullet was found?

Stella discovers the .50-caliber shell casing at the diner where the ambush occurred, along with additional casings from a .45-caliber weapon

internal ballistics

what happens in the weapon

external ballisitics

what happens after the bullet exits the weapon

terminal ballistics

what happens when the bullet hits the target

Striation Marks

Every bullet can be matched to a particular weapon through comparing striation marks

Distance Determination

The process of determining the distance between the firearm and the target, usually based on the distribution of powder patterns or the spread if a shot pattern.

Ballistics evidence collection and analysis involves

identifying and comparing unique markings on bullets and cartridge cases to link them to specific firearms