forensics ballistics test

Compare "bullets" to "cartridges."

"Bullet" refers to the projectile(s) which actually exits the barrel of the gun when fired the bullet is what you're putting in the cartridge

Barrel inches away

"stippling" of the burning powder around the actual bullet entry way No star pattern No "blow back

Barrel just off skin

- no star pattern so.. not ON skin No stippling from g.p. so.. TOO close for inches away Barrel burns like on skin so.... JUST off skin

½ Jacketed

A lead bullet coated with copper half way up the exposed portion of the bullet Used primarily for hollow points Copper improves exit velocity Lead promotes mushrooming

Full Metal Jacket

A lead bullet completely coated in copper Copper improves exit velocity Used to hold the shape of the bullet in an effort to maximize penetration

What are the 4 kinds of bullet wounds? Describe each type.

Barrel on skin Barrel just off skin Barrel inches away Shot from a distance

Lead Bullets

Cheap Dense Soft Easy to mold

What class evidence can we obtain from fired bullets?

Different gun manufacturers use different rifling techniques. These techniques impart the class characteristics on a fired bullet. Number of impressions Width of impressions Depth of impressions Angle of impressions

Barrel on skin

Distinctive star pattern, so... Energy from the gunshot forced back out entryway "blowback" NO burnt gunpowder marks around entryway, so... ALL gunpowder delivered inside entryway singeing the interior (black area)

Why do investigators analyze bullet wounds?

Eyewitness accounts often are not accurate, so investigators examine bullet wounds to confirm stories. Determining which wound is the entrance and which is the exit is an important step in determining what happened at a crime scene.

What individual evidence can we get using cartridges and casings?

Firing pin marks left on the spent cartridge casings can also be used to identify a firearm left on the bottom of the cartridge when the firing pin hits it to fire the shot BREECH MARKS PLAY A VITAL ROLE IN DETERMINING IF A CERTAIN BULLET WAS FIRED FROM A FIREARM. BREECH MARKS ARE FOUND ON THE REAR OF A FIRED CARTRIDGE

What are the 3 categories of ballistics?

Internal ballistics External ballistics Terminal ballistics

Identify and describe the different types of firearms.

Long guns - require the use of two hands during firing (rifles fire bullets, shotguns fire pellets or slugs) Handguns - (pistols fire one and revolvers fire from a revolving cylinder) can be fired using one hand. They are divided into two subcategories, revolvers (holds 6 bullets) and semiautomatic (can hold up to 10 in a clip, more in a military or police grade clip)

Describe the ways manufacturers create rifling.

Made by drilling spiral grooves into barrel One modern method uses broach cutters to cut all the grooves simultaneously by forcing cutter down barrel and rotating the cutter. Another modern method uses a "button' with the desired number of grooves that's forced down a barrel at high pressure. Alternative is to use a mandrel, also known as hammer forging. The mandrel with correct (negative) rifling is inserted into an oversized bore and the barrel compressed around the mandrel by rolling or hammering the barrel. The last option is to etch the rifling pattern into a pre-drilled core using electricity and acid, known as electrochemical etching

Round Nose

Maximum penetration Cheapest shape to manufacture Easily loads into chambers

What happens to a bullet when it hits a target?

Most bullets tend to mushroom when they hit a target. Some bullets nearly disintegrate. Right are bullet fragments from a ½ jacketed hollow point.

Hollow Point

Spreads or mushrooms on impact Causes additional damage to target Inhibits penetration

What individual evidence can we obtain from fired bullets?

Striations (small lines) - microscopic imperfections from rifling tools or chips of steel from broach cutter. No two rifle barrels, even those made in succession, will have identical striation markings. With the aid of a comparison microscope, compare these "test fires" to the crime scene bullets Striations must be identical for a positive match

Explain how a firearm works.

The firing pin hits the base of the cartridge, igniting the primer powder. The primer powder sparks through the flash hole to the main propellant supply. The pressure of the explosion pushes the bullet from the casing into the barrel. The bullet follows the lands and grooves spiraling out of the barrel.

what is internal ballistics?

The study of the processes occurring inside a firearm when a shot is fired. It includes the study of various firearm mechanisms and barrel manufacturing techniques; Factors influencing internal gas pressure; and Firearm recoil

What is terminal ballistics?

The study of the projectile's effect on the target or the counter-effect of the target on the projectile

What is external ballistics?

The study of the projectile's flight from the moment it leaves the muzzle of the barrel until it strikes the target.

What is gunshot residue?

These residues are the traces of smoke and particles of unburned powder carried sideways from the firearm by the expansion of gases as the bullet is fired. Gunshot residues containing nitrates can stick to the person holding the firearm and leave evidence on the shooter.

How can we calculate trajectory?

USE TAN

Wadcutter

Used exclusively as a practice load Minimizes penetration Rips a hole in target paper which is visible by the shooter

What evidence can we get from forensic ballistics?

What type of firearm was used? What was the caliber of the bullet? How many bullets were fired? Where was the shooter standing? What was the angle of impact? Has this firearm been used in a previous crime?

What evidence can we obtain from GSR?

Who fired a firearm At close range, the distance between the victim and the shooter may be estimated by examining the GSR pattern on victim

What is the anatomy of a cartridge?

bullet primer powder anvil and flash hole headstamp

What are the common types of terminal ballistics examinations?

determination of the distance between firing point and target establishing whether or not a particular wound was caused by a fired bullet determining the caliber and type of projectile that caused bullet damage or gunshot wound examination of bullet exit/entrance by examining the holes in targets, or the wounds in biological tissue examination of ricochet possibilities and fired projectiles

Compare and contrast entry wounds with exit wounds?

entrance wounds are smaller than exit wounds. Because the skin is elastic, it stretches when a bullet enters the body causing the entrance wound hole to be smaller than the bullet. Exit wounds are larger because the bullet may move and gather tissue and bone and push that out as it leaves.

What are the most common types of internal ballistics?

examining mechanism to determine the causes of accidental discharge examining homemade devices (zip-guns) to determine if they are capable of discharging ammunition effectively microscopic examination and comparison of fired bullets and cartridge cases to determine whether a particular firearm was used

What is forensic ballistics?

is the scientific analysis or interpretation of all ballistic related evidence with the purpose of interpreting and establishing the facts in a shooting related crime

What 5 factors determine the seriousness of a gunshot wound?

kinetic energy of the bullet distance to the target type of tissue tumbling (flipping around or going straight through) bullet design ex. hollow point, vs. round nose etc.

What class evidence can we get using cartridges and casings?

make and model of gun? how many bullets were fired at the crime scene

What is the caliber of a bullet?

measure of the diameter of the cartridge

How do we obtain GSR?

police swab suspects hand to collect any residue present analysis use electron microscope to inspect the swab

What is bullet trajectory?

the path of the propelled bullet. From the angle of trajectory, the path back to the shooter can be traced.

What is rifling & explain how we can use rifling as evidence?

the process of making helical grooves in the barrel of a gun or firearm, which imparts a spin to a projectile around its long axis. a barrel will impress a negative impression of itself on the sides of the bullet