CSI Quiz 4

handguns

designed to be fired and held with one hand

long guns

designed to be fired with both hands

single shot

- ammunition loaded one at a time

- lever action rifles

- bolt action rifles

- break open, derringer

revolver

- rotating cylinder

- each cylinder holds one cartridge

- cylinder rotates with the trigger pull

- 4 to 24 rounds of ammunition

- cartridges don't leave after shot

revolver CSI concerns

each cylinder holds one cartridge and holds it after it is fired; shell casings may not be at the scene

semiauto

one round fires with each trigger pull

-referred to as self-loading

- energy from one fired round loads the next round

automatic

- fires multiple shots with a single trigger pull

- cartridges are held in a magazine

- may be a handgun or long gun (assault rifles, machine guns, submachine guns)

automatic concerns

- easily reloaded

- both leave behind shell casings

- shell locations may provide shooter placement

- may identify weapon

shot gun

- barrels are smooth, not rifled

- pump action

- side by side, over/under

- impact patterns, will spread the farther it goes from the person shooting

firearm safety concerns

1. inherent dangers exist due to the nature of firearms

2. all firearms should be considered loaded - no exceptions

3. each crime scene investigator should inspect firearms personally

4. firearms should never be pointed at anything you would not be prepared to shoot

categories of toolmarks

1. fracturing

2. impressions

3. pinching

4. scraping

5. shearing

6. slicing

impressions

- caused by the indentation or depression of one object upon another

- common examples: hammers, mallets

pinching

- caused when an object is squeezed between two points

- pliers

scraping

- caused when a sharp or angular object is drawn across another

- common sources: nails, keys, screwdrivers

shearing

- caused by offsetting cutting blades

- common sources: scissors, tin snips, wire cutters, bolt cutters

slicing

- caused by movement of a sharp object through another

- common examples: knives, swords

NIBIN hits

- a NIBIN hit occurs when two or more firearms ballistic evidence acquisitions identified as a confirmed match by a firearms examiner

- tiny markings can identify firearms

- can link two different crimes

basic considerations for toolmarkings

- quality of tool marks --> dependent on the material (1) the tool or (2) the damaged object

elements of GSR

- does not explode

- during the burning process 3 chemicals combine (antimony, barium, lead)

- samples collected from someone's person may contain these elements for positive results and contain these elements for positive results in GSR analysis

- common collection locations include hands and face

- composed of 2 substances (propellant + primer)

ammunition

- shotgun - shotshell (buckshot, birdshot or slug)

- rimfire - primer is loaded in the rim, .22 caliber

- centerfire - primer loaded at the center of cartridge

- ball, semi jacketed, full metal jacket, hollow point

firearm nomenclature

important so you can identify where you took evidence from

GSR testing and collection concerns

- multiple sources of the three chemicals other than firearms

- multiple sources of cross contamination

- considered valid for only 4-6 hours after shooting

legality of GSR testing

can be taken with probable cause because of exigent circumstances because it goes away over time

firearms found underwater

keep it in the same type of water you found it in

importance of firearm evidence

- ballistic matches - projectiles to weapons

- NIBIN matches to shell casings

- gunshot residue

- distance determinations

- DNA

- fingerprints

different types of ammunition in connection to different firearms