RO Forensic Science & Analysis 2 — Questions and Answers
Question 1: What is gunshot residue (GSR) primarily composed of?
- Lead, barium, and antimony particles (Correct answer)
- Carbon monoxide and nitrogen gas
- Copper and zinc oxide flakes
- Sulfur dioxide and potassium nitrate
Correct answer: Lead, barium, and antimony particles
GSR consists of microscopic particles of lead, barium, and antimony released from the primer upon firing.
Question 2: Which technique is considered the gold standard for confirming GSR on a suspect's hands?
- Atomic absorption spectroscopy
- Scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX) (Correct answer)
- Gas chromatography
- Infrared spectroscopy
Correct answer: Scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX)
SEM-EDX simultaneously identifies the morphology and elemental composition of individual GSR particles, making it the definitive confirmatory method.
Question 3: On a range incident scene, how should a spent cartridge case be collected to preserve forensic value?
- Pick it up by the case mouth and drop it in a paper bag
- Use gloves, pick it up by the rim, and place it in a labeled rigid container (Correct answer)
- Leave it in place until photographed, then sweep it into a plastic bag
- Mark it with a felt-tip pen for identification before bagging
Correct answer: Use gloves, pick it up by the rim, and place it in a labeled rigid container
Handling by the rim with gloves minimizes contamination of the case body where fingerprints and GSR may be present, and rigid containers prevent damage to extractor marks.
Question 4: What does 'chain of custody' mean in the context of range forensic evidence?
- The sequence of shooting positions used during a course of fire
- A documented, unbroken record of who handled evidence from collection to court (Correct answer)
- The order in which spent rounds are recovered from a berm
- A logbook tracking firearm ownership transfers
Correct answer: A documented, unbroken record of who handled evidence from collection to court
Chain of custody is the chronological documentation proving that evidence was not tampered with between collection and presentation in legal proceedings.
Question 5: Which rifling characteristic is most commonly used to link a recovered bullet to a specific firearm?
- Bullet weight and caliber
- Land and groove impressions and twist rate (Correct answer)
- Bullet jacket material composition
- Powder residue inside the barrel
Correct answer: Land and groove impressions and twist rate
The number, width, and twist direction of lands and grooves are unique to individual barrels and are impressed on fired bullets.
Question 6: A range officer finds an unfired round near a shooting position after an incident. What is the correct first step?
- Unload the round to make it safe before packaging
- Photograph it in place, mark the location, then carefully package it without handling the primer (Correct answer)
- Throw it in the range's ammunition disposal bucket
- Fire it downrange to determine if it is functional
Correct answer: Photograph it in place, mark the location, then carefully package it without handling the primer
The round must be documented in place photographically before collection; it should not be altered or rendered inert because its condition is itself evidence.
Question 7: What is the primary purpose of documenting bullet trajectory on a range incident scene?
- To estimate the shooter's marksmanship score
- To reconstruct the shooter's position, angle of fire, and sequence of events (Correct answer)
- To determine the caliber of ammunition used
- To calculate the firearm's muzzle velocity
Correct answer: To reconstruct the shooter's position, angle of fire, and sequence of events
Trajectory analysis allows investigators to reconstruct where the shooter was standing, the direction of fire, and how the incident unfolded.
RO Forensic Science & Analysis 2
What is gunshot residue (GSR) primarily composed of?