CFI Fire Scene Management 3 — Questions and Answers
Question 1: Under NFPA 921, what is the recommended approach when two valid hypotheses exist for the cause of a fire?
- Choose the hypothesis that favors the property owner
- Accept both hypotheses simultaneously as the official cause
- Test each hypothesis against all available data and eliminate those not supported (Correct answer)
- Default to accidental cause when evidence is ambiguous
Correct answer: Test each hypothesis against all available data and eliminate those not supported
NFPA 921 directs investigators to apply the scientific method, testing each hypothesis against all data and eliminating those that cannot be supported by the evidence.
Question 2: What is the primary hazard investigators face when re-entering a fire-damaged structure?
- Residual smoke odor affecting air quality samples
- Structural collapse of compromised walls, floors, and roofs (Correct answer)
- Contamination of accelerant samples by suppression water
- Electrical shock from downed power lines only outside the structure
Correct answer: Structural collapse of compromised walls, floors, and roofs
Structural collapse is the leading cause of injury and death to investigators working in fire-damaged buildings.
Question 3: Which type of evidence collection container is preferred for liquid accelerant samples?
- Plastic zip-lock bags
- Unsealed paper bags
- New, unused paint cans with tight-fitting lids or approved nylon bags (Correct answer)
- Glass jars with rubber seals
Correct answer: New, unused paint cans with tight-fitting lids or approved nylon bags
New, unlined paint cans or approved nylon/polyester evidence bags are preferred because they do not off-gas or contaminate accelerant samples the way plastic or rubber materials can.
Question 4: A fire investigator is called to a scene three days after suppression. What is the first step before beginning examination?
- Begin digging in the area of most severe damage
- Obtain proper legal authority to enter and search the scene (Correct answer)
- Interview neighbors about what they observed
- Review the fire department's incident report only
Correct answer: Obtain proper legal authority to enter and search the scene
Before any physical examination, investigators must ensure they have proper legal authority—consent, administrative warrant, or criminal warrant—to enter and search the scene.
Question 5: What does 'low burn' evidence at a fire scene typically indicate to an investigator?
- The fire was suppressed quickly before it could rise
- A flammable liquid may have been used and pooled on the floor (Correct answer)
- The fire started in an upper floor and burned downward
- The electrical system failed at the base of the walls
Correct answer: A flammable liquid may have been used and pooled on the floor
Low burn patterns on floors and lower wall surfaces can indicate the presence of flammable liquids, which pool and ignite at floor level.
Question 6: Which action during debris excavation best preserves the integrity of fire scene evidence?
- Using heavy equipment to quickly clear large debris fields
- Removing debris in layers from top to bottom, documenting each layer (Correct answer)
- Hosing down the debris to reduce dust before examination
- Mixing debris from multiple rooms to save time
Correct answer: Removing debris in layers from top to bottom, documenting each layer
Systematic layer-by-layer removal documents the stratigraphy of the debris field, which can reveal information about fire progression and the location of ignition sources.
Question 7: A fire investigator suspects that a witness is also a person of interest. What is the best practice?
- Immediately arrest the witness to prevent evidence tampering
- Continue interviewing them as a witness without informing law enforcement
- Coordinate with law enforcement and ensure proper legal protocols are followed (Correct answer)
- Disregard their testimony entirely
Correct answer: Coordinate with law enforcement and ensure proper legal protocols are followed
When a witness becomes a person of interest, the investigator must coordinate with law enforcement to ensure constitutional rights are protected and the investigation is not compromised.
CFI Fire Scene Management 3
Under NFPA 921, what is the recommended approach when two valid hypotheses exist for the cause of a fire?