SCI-255 Exam 3 Study Guide Questions with Complete Solutions cartridge components - Correct Answers Cartridge case Primer Propellant (gunpowder) Bullet or projectile revolvers and semiautomatic pistols - Correct Answers most common firearms involved in criminal cases Rimfire (RF) cartridge - Correct Answers has the priming compound encased around the rim Centerfire (CF) cartridge - Correct Answers has the priming compound encased as a central primer and may have a rimmed, rimless, or semi-rimmed cartridge case Three general cartridge shapes - Correct Answers straight, tapered, bottlenecked
Shotshells - Correct Answers Plastic shells filled with:
shot (projectiles) wad gunpowder primer Rifling - Correct Answers The spiral pattern of lands and grooves in the barrel of a firearm. Stabilizes the bullet.Smooth bore weapon - Correct Answers has no rifling present in the barrel (ex: shotgun) Class characteristics of a firearm - Correct Answers caliber, number of lands and grooves, width of lands and grooves, direction and rate of twist 1 / 3
Firearm caliber - Correct Answers expressed are bore diameter (d) or groove diameter (D) measured in either hundreds or thousands of an inch^2 barrel diameter may be different from the caliber Class characteristics of Fired Bullets - Correct Answers caliber, #lands/grooves, direction of twist.Impressions on bullet are referred to as land and groove impressions Fired cartridge case - Correct Answers have an impression of the breech face, an ejector mark from the ejector, override and gouge marks from the extractor Fired cartridge case pt 2 - Correct Answers fired from semiautomatic, automatic, and revolvers will typically have chamber striations and firing pin impression Lab Examinations of Firearm Evidence - Correct Answers ID the firearm, GSR Determine muzzle to target distant, functionality, bullet trajectory and sequence of firing Document condition of firearm - Correct Answers loaded or unloaded?hammer cocked?safety on or off?When unloading firearm - Correct Answers ammunition in the chamber?loaded magazine in semi auto?cartridge cases or ammunition in revolver?Identification of weapon - Correct Answers record make, model, serial number on tag tied to the trigger guard Areas not likely to retain fingerprints (gun) - Correct Answers handle knurls or checkered grip slide unloading revolvers - Correct Answers -mark cylinder to indicate which was in line with the barrel 2 / 3
-record position of each round in the cylinder -package each separately -Indicate chamber location on packaging Unloading automatic/semi-auto - Correct Answers -point gun down -release magazine -pull back slide to release the ammo in chamber -package magazine, firearm and chamber ammo separate -don't unload magazine Weapons found in water - Correct Answers place in a container with the same water covering the weapon, if not rusting will occur Transporting weapons to lab - Correct Answers -personal delivery is preferred -live ammunition cannot be shipped through US mail Bullets embedded in wood or plaster - Correct Answers -sketch location of bullet hole -cut/saw out the wall portion with the bullet -do not dig out Removal from dead person (ME) - Correct Answers -xray body -remove with rubber tipped or plastic forceps, or fingers -bullet packaged as is Cartridge case location - Correct Answers -important for reconstruction -sketch and measure the position of all ejected cartridge cases -package each separately Shot wads (shotguns) - Correct Answers -travel behind the shot -same method for ejected cartridge cases
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