FBI Evidence Collection & Preservation 2 — Questions and Answers
Question 1: When collecting trace evidence from a shooting victim's clothing, what technique should be used first before removing the garment?
- Shake the clothing to dislodge particles
- Photograph and tape-lift trace evidence in place (Correct answer)
- Place the garment directly into a plastic bag
- Cut the clothing along the bullet wound immediately
Correct answer: Photograph and tape-lift trace evidence in place
Photographing and tape-lifting trace evidence in place prevents loss or contamination before the garment is removed or packaged.
Question 2: What is the primary reason firearms evidence should be packaged in paper rather than plastic bags?
- Paper is more durable and tear-resistant
- Paper allows moisture to escape, preventing mold and DNA degradation (Correct answer)
- Plastic bags are too expensive for routine use
- Paper bags are easier to seal with evidence tape
Correct answer: Paper allows moisture to escape, preventing mold and DNA degradation
Paper packaging is breathable, allowing moisture to escape and preventing the growth of mold that could destroy biological evidence.
Question 3: An agent discovers a handgun submerged in a pond. What is the correct initial handling procedure?
- Drain the water immediately and dry the firearm before packaging
- Insert a pencil into the barrel to lift and transport the weapon
- Package the firearm with water in a sealed container to preserve evidence (Correct answer)
- Wipe down the exterior to reveal latent prints before packaging
Correct answer: Package the firearm with water in a sealed container to preserve evidence
Submerged firearms should be kept wet in their recovered state to preserve fingerprints and DNA that would be destroyed by drying.
Question 4: What does the term 'locard's exchange principle' mean in the context of crime scene evidence?
- Evidence must be exchanged between labs for verification
- Every contact between two objects leaves a trace on each (Correct answer)
- Chain of custody must be exchanged with prosecutors before trial
- Digital evidence must be copied before the original is examined
Correct answer: Every contact between two objects leaves a trace on each
Locard's Exchange Principle states that every contact leaves a trace — the perpetrator takes something from and leaves something at the scene.
Question 5: During a shooting scene investigation, bullet trajectory rods are used primarily to:
- Measure the caliber of rounds fired
- Establish the angle and direction from which shots were fired (Correct answer)
- Recover fragmented projectiles from walls
- Determine the muzzle velocity of the firearm used
Correct answer: Establish the angle and direction from which shots were fired
Trajectory rods are inserted into bullet holes to visually establish the angle and potential origin point of each shot.
Question 6: Which type of gunshot residue (GSR) collection kit is used on a living suspect's hands?
- Swab kit using sterile cotton moistened with distilled water
- Adhesive stub lift kit analyzed by SEM-EDX (Correct answer)
- Filter paper collection placed on hands for 30 seconds
- Cellophane tape applied and peeled from palms and backs of hands
Correct answer: Adhesive stub lift kit analyzed by SEM-EDX
The standard GSR collection method uses adhesive carbon-coated stubs analyzed by scanning electron microscopy with energy-dispersive X-ray (SEM-EDX).
Question 7: How long after a shooting incident is GSR typically detectable on an unwashed shooter's hands?
- Up to 30 minutes
- Up to 4–6 hours (Correct answer)
- Up to 24 hours
- Up to 72 hours
Correct answer: Up to 4–6 hours
GSR is typically detectable on unwashed hands for approximately 4–6 hours, after which normal activity causes significant particle loss.
FBI Evidence Collection & Preservation 2
When collecting trace evidence from a shooting victim's clothing, what technique should be used first before removing the garment?