Ballistics & Impressions

Review

What term is associated with this definition?

A discipline mainly concerned with determining whether a bullet or cartridge was fired by a particular weapon.

Firearm Identification

What are the names of the markings/impressions placed in the barrel of a gun?

LandsGrooves

Rifling occurs in what part of the gun?

The barrel.

What is the purpose of rifling a gun?

It makes the projectile spin when it is fired, which gives it more accuracy.

The __________ is the diameter of the bore of a gun.

caliber

What are the four parts in or on a cartridge case? (Including the case)

Cartridge CasePrimerGunpowderBullet

DOUBLE POINTS!!!

Briefly explain how a bullet is fired.

A firing pin hits the primer, which causes a spark. This spark then causes the gun powder to explode and expand, which in turn sends the bullet down the barrel out of the gun.

True or False.

Guns of the same manufacturer have the exact same markings in their barrels.

FALSE!These markings leave unique

striations or impressions on a bullet. This allows a bullet to be traced back to a particular firearm.

Cartridge Cases are classified by which of the following:◦Manufacturer◦Shape ◦Caliber◦Composition

All of them.

Firing pin impressions would be left on what?

And can they be used as an individual characteristic to identify it?

Cartridge caseYes. Firing pin impressions are unique to

the type of gun.

Are there any other characteristics that could be used to identify a cartridge case found at a crime scene?

Breech Face MarksEjector MarksExtractor Marks

DOUBLE POINTS!!!

Is a cartridge case typically ejected from the gun?

If so explain.

Yes.The opposite reaction of the bullet being

fired out sends the case against the breech wall (which along with the extracting pin and ejector they throw the spent shell casing from the chamber of the gun).

What type of guns typically have smooth barrels?

Shotguns

Explain how gunpowder would be left on a target if the suspect were standing close.

The closer they are, the more residue is left.

What type of test is often used to lift gunpowder residue?

Dermal Nitrate Test

Impressions Evidence – use your notes.