Lecture 3: Crime Scene Analysis Flashcards
Processing a firearm crime scene steps
- Identify Evidence
- Notes & Sketches/Documentation
- Measurements
- Establishing Trajectories
- Chemical Tests (GSR)
- Initial Opinion
needs in a firearm crime scene
positions of injured
bullet position & cartridge
position of bullet damage and recovered bullets
position of shooter
notes to remember in collecting firearm evidence
they are durable (ie. can have finger prints, DNA, hair evidence)
remembering safety
photograph and document
notes of firearm analysis
safety check everything
no live rounds
preserve any other evidence removed
setps of a gun firing
- ammunition pushed into chamber
- hammer cocks
- trigger pulled and hammer releases
- hammer strikes firing pin which ignites the primer
- primer (through the flash hole) then ignites the propellant pushing the bullet through the barrel
- bullet exits along with many gasses in the gun
what happens when a bullet hits glass
fracturing at point of impact
what is the coning effect
where the caves on the other side of impact and the shards of glass are spread there
what is a secondary projectile
a object that was impacted by the bullet and is turned into a projectile possibly injuring or damaging another
what is a trajectory rod
a trajectory rod is used to visually represent the point of impact and direction of trajectory
what info should be gathered about the bullets
the # of shots fired, the type of weapon and the caliber of the weapon
what are some possible reasons for no cartridge cases
not self loading (revolver), picked them up, too spread out, is a rifle
how are bullets examined
visually examined
features on a bullets for IDs
headstamp, manufacturer, caliber, dealer, manufacturing date and type of firearm
indication of bullet being fired
rifling pattern, impact damage, firing pin mark, inside of the cartridge is black, ejector/extractor mark, breech face
first thing to do when arriving on a scene
general assessment: walk through, making a plan, noting transient and non transient evidence
where is the most common places that the cartridge cases fall
to the right of the right back
after a walkthrough of the scene a forensic investigator continues to
photograph and document all of the evidence present
after taking photographs of the scene what is the next step
ID marking the evidence, accurate measurements of all, collecting cases
after IDing all the evidence at the scene what is the next steps
it is to locate all bullet damage (bullets, bullet fragments, secondary projectile) and ID them with trajectory rods
after IDing the bullet damage the last step of processing a firearm scene is
doing a sodium rhodizonate test for GSR, also looking for bullet wipe
expert info needed before leaving the scene
minimum shots fired, caliber, type of weapon, trajectory
what kind of tools is need in handling firearms
plastic as to not damage the weapon or any other evidence
when handling a gun avoid:
losing GSR (unnecessary handling), dropping the gun, and metal tools
Safety First, what should be done when a firearm is found
examined for live round, unload gun if live
