Chapter 22 — Self-Check Quiz

25 questions: multiple choice and short answer. Try them closed-book. The answer key is in the collapsed block at the bottom.

Multiple choice

1. The consensus standard that governs modern fire-and-explosion investigation methodology is: - A. The Daubert standard - B. NFPA 921 - C. ISO/IEC 17025 - D. The PCAST report

2. "Origin and cause" determination establishes: - A. Who set the fire and why - B. Where the fire began and what started it - C. The temperature of the fire and its duration only - D. The insurance value of the structure

3. Flashover is best described as: - A. The moment a single item finishes burning - B. The near-simultaneous ignition of all exposed combustible surfaces in a room, driven by radiant heat from the hot-gas layer - C. A type of accelerant - D. The cooling of a fire after extinguishment

4. The three legs of the fire triangle are: - A. Fuel, oxidizer, heat - B. Smoke, flame, ash - C. Origin, cause, spread - D. Gasoline, kerosene, lighter fluid

5. "Crazed glass" (a fine network of cracks in window glass) is actually caused by: - A. An accelerant burning unusually hot - B. Rapid cooling — cold water (the fire hose) hitting hot glass - C. The deliberate breaking of windows by an arsonist - D. Flashover alone

6. Low, irregular, "pool-shaped" burn patterns on a floor: - A. Prove a liquid accelerant was poured - B. Are produced routinely by ordinary post-flashover fires with no accelerant present - C. Can only occur in arson - D. Indicate the exact origin of the fire

7. "Alligatoring" (shiny, blistered char) reliably indicates: - A. The presence of an accelerant - B. A fast, hot fire - C. Essentially nothing about fire speed, temperature, or accelerant — only that wood burned - D. The point of origin

8. The "negative corpus" reasoning that NFPA 921 rejects is: - A. Confirming an accelerant by GC-MS - B. Concluding a fire was incendiary purely by eliminating all identified accidental causes, without affirmative evidence of a set fire - C. Classifying a fire as "undetermined" - D. Collecting a comparison sample

9. When the evidence does not allow the cause to be established to a reasonable degree of scientific certainty, the honest classification is: - A. Incendiary - B. Accidental - C. Undetermined - D. Natural

10. An accelerant is confirmed: - A. By the scene investigator's trained eye and nose - B. By the presence of a "pour pattern" - C. By laboratory instrumentation (GC-MS) identifying ignitable-liquid residue - D. By the absence of an accidental cause

11. The reason a modern foam sofa undermines "an unusually hot fire proves accelerant" is that: - A. Foam cannot burn - B. Modern synthetic furnishings have a very high heat release rate — comparable to a small gasoline fire — so an intense fire is normal - C. Foam always requires an accelerant to ignite - D. Sofas are fireproof by law

12. A negative ignitable-liquid-residue result from fire debris means: - A. No accelerant was used, definitively - B. The fire was accidental - C. No ignitable liquid was detected — but a hot enough fire can consume the liquid, so absence does not prove none was used - D. The sample was contaminated

13. Suspected accelerant debris should be collected into: - A. An ordinary plastic grocery bag - B. An airtight, vapor-tight container such as a clean unused metal can or a nylon evidence bag - C. A paper envelope - D. An open cardboard box

14. A comparison (control) sample of unburned material is collected to: - A. Increase the sample size - B. Distinguish a genuine foreign ignitable liquid from the petroleum-derived background that synthetic materials normally emit when heated - C. Replace the suspected-accelerant sample - D. Measure the fire's temperature

15. Multiple, separate, unconnected points of origin support an incendiary finding because: - A. They are one of the debunked indicators - B. A single accidental fire begins in one place, so independent origins are difficult to explain innocently - C. They prove who set the fire - D. They indicate flashover occurred

16. Cameron Todd Willingham was: - A. Exonerated and released before his execution - B. Executed by Texas in 2004 on fire indicators that maturing fire science had already refuted - C. Never actually charged - D. Convicted on DNA evidence

17. The fire scientists associated with re-examining the Willingham fire science include: - A. Barry Scheck and Peter Neufeld - B. Gerald Hurst (before the execution) and Craig Beyler (for the Texas Forensic Science Commission, after) - C. Edmond Locard and Calvin Goddard - D. The PCAST committee

18. Han Tak Lee's case ended with: - A. His execution - B. His release after roughly a quarter-century, when courts found the discredited fire science could no longer sustain the conviction - C. A retrial and reconviction - D. A finding that the fire was accidental beyond doubt

19. On the validity spectrum, fire investigation is best described as: - A. Sitting at a single fixed point near the discredited end - B. Spanning the spectrum: debunked indicators near the bottom, modern fire-dynamics + confirmed-ILR work much higher - C. Equivalent to single-source DNA throughout - D. Entirely discredited like bite marks

20. In the cold case, the Mill Creek fire is found incendiary on the basis of: - A. Crazed glass and alligatoring - B. Negative corpus (no accidental cause found) - C. Multiple origins plus an ignitable-liquid (gasoline) distribution pattern, explicitly not the debunked indicators - D. The jailhouse informant's testimony

Short answer

21. In two sentences, explain why the existence of flashover was so devastating to the old indicator-based fire investigation. (What did it reveal the indicators had never actually been measuring?)

22. State the affirmative-evidence standard for an incendiary finding, and contrast it with negative-corpus reasoning. What is the honest classification when affirmative evidence is absent?

23. A laboratory chemist and a scene investigator testify in the same arson trial. Write the sentence the chemist can honestly say about a confirmed gasoline residue, and the separate, weaker claim the investigator makes by saying it was "poured deliberately to set the fire." Why must the two not be conflated?

24. In the cold case, the autopsy found no soot in Marcus Diallo's airways (Chapter 11). Explain how this changes what the fire evidence in this chapter is for, and why the fire finding does not identify a person.

25. Why does the sincerity of the Willingham investigators make the case more disturbing rather than less? Connect it to the idea (Chapter 6) that an honest examiner can be the vehicle for junk science.

Answer key (click to expand) **Multiple choice:** 1-B · 2-B · 3-B · 4-A · 5-B · 6-B · 7-C · 8-B · 9-C · 10-C · 11-B · 12-C · 13-B · 14-B · 15-B · 16-B · 17-B · 18-B · 19-B · 20-C **Short answer (model points):** **21.** Flashover produces — in *any* ordinary accidental fire that reaches it — the low, floor-level, "pour-shaped" burn patterns the old folklore treated as the exclusive signatures of a poured accelerant. So flashover revealed that the indicators could not distinguish set fires from accidental ones at all: they had never been measuring "arson," only the normal end-state of a fully developed fire. **22.** The **affirmative-evidence standard** requires that an incendiary finding rest on positive physical evidence that the fire was deliberately set — e.g., a confirmed ignitable liquid in a deliberate distribution pattern, genuinely multiple unconnected origins, or an incendiary device. **Negative corpus** instead backs into "arson" merely by eliminating identified accidental causes, which is invalid because (a) the accidental cause may have been destroyed by the fire and (b) the proper classification when the cause cannot be affirmatively established is **undetermined**, not incendiary. **23.** **Chemist (validated):** "The chemical pattern recovered from this debris is consistent with gasoline." **Investigator (weaker, contestable):** "The gasoline was poured deliberately in this pattern to set the fire." The first is an analytical-chemistry identification with a strong, reproducible foundation; the second is a scene interpretation that the old folklore creeps back into. Conflating them lets the unassailable "it's gasoline" lend false strength to the contestable "it was deliberately poured" — two different claims with two different strengths. **24.** No soot in the airways shows Diallo was *dead before the fire*, so the fire did not kill him — it burned an already-dead homicide victim. The fire evidence is therefore no longer answering "accident or homicide?" (the autopsy settled that) but "how the fire fits the staging" — i.e., whether the fire was deliberately set to destroy evidence. The fire finding establishes a *deliberate fire*, not a *person*: arson is a determination about the fire's cause, and no name attaches to the accelerant; linking a person requires other evidence (soil, digital, DNA). **25.** The Willingham investigators were, in all likelihood, applying methods their entire field had taught them and sincerely believed in — they were not committing fraud. That is more disturbing because it means junk science needs no malice to kill: a sincere expert is *more* persuasive to a jury than a liar, and an honest examiner using an unvalidated method in perfect good faith still misleads the court (Chapter 6, §6.1). The danger is structural — a confident method no one ever tested — not the dishonesty of any individual.