Chapter 36 — 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. Wildlife forensics most foundationally answers: - A. Who owns the animal - B. What species the biological evidence is (and whether it is protected), and sometimes where it came from - C. The market value of the contraband - D. The age of the poacher

2. Identifying a sample as "elephant" rather than "cow" is, in the book's terms: - A. An individual characteristic - B. A class characteristic - C. A confession - D. An accident reconstruction

3. The only full-service laboratory in the world dedicated to wildlife crime, and the official lab for the CITES treaty, is: - A. The FBI Laboratory - B. The U.S. Fish and Wildlife Service National Fish and Wildlife Forensic Laboratory (Ashland, Oregon) - C. The state crime laboratory - D. The National Transportation Safety Board

4. Geographic-origin DNA for elephants works by: - A. Reading a GPS chip in the tusk - B. Comparing the tusk's DNA against a reference map of how DNA varies across the species' range (population allele frequencies) - C. Smelling the ivory - D. Measuring the tusk's length

5. The central limit on a DNA species identification is usually: - A. The price of the test - B. The completeness of the reference database (the true species must be in it) - C. The color of the sample - D. The weather at the seizure

6. Environmental forensics attributes a pollutant to a source mainly by: - A. Guessing which company is nearby - B. Chemical "fingerprinting" — comparing the pollutant's detailed chemical pattern (by GC-MS) against candidate sources - C. Asking the regulator - D. Reading the company's annual report

7. A pollutant's chemical "fingerprint" is, properly understood: - A. A unique mark identifying one source in all the world - B. A class characteristic shared by all product of that type/batch/process — so attribution is probabilistic - C. The same as a human fingerprint - D. Proof of intent

8. In oil-spill fingerprinting, biomarker ratios are emphasized because: - A. They are the cheapest to measure - B. They are relatively resistant to weathering, so a spill that has sat for days can still be compared to its source - C. They reveal the captain's name - D. They evaporate first

9. Failure analysis is best described as: - A. Guessing why something broke - B. The systematic determination of how/why a structure or component failed, by testing hypotheses against the physical evidence - C. Replacing the broken part - D. A type of accident reconstruction only

10. "Beach marks" (progression marks) on a fracture surface indicate: - A. The part was painted - B. Fatigue — a crack that grew a little with each stress cycle before final rupture - C. The part was brittle from the start - D. An explosion

11. A forensic engineer concludes a cause "because no other cause could be found." This is: - A. Sound reasoning - B. The negative-corpus fallacy (Chapter 22) in a hard hat — a cause needs affirmative evidence - C. Required by Kumho Tire - D. A class characteristic

12. Accident reconstruction is, by analogy in this book, most like: - A. DNA typing - B. Bloodstain pattern analysis — geometry and physics reconstructing past events from physical residue - C. Forensic accounting - D. Odontology

13. A skid mark yields a speed that is: - A. The exact speed at the moment of the crash - B. A minimum speed and a range (it captures only speed lost after the wheels locked, and depends on an estimated friction value) - C. The maximum the car could ever go - D. Irrelevant to the reconstruction

14. An event data recorder (EDR) is valuable partly because: - A. It can be edited by either party - B. It is a recorded log, harder to read one's expectation into than ambiguous physical marks — a partial antidote to bias - C. It replaces all physical evidence - D. It identifies the driver's motive

15. Kumho Tire Co. v. Carmichael (1999) matters to forensic engineering because it: - A. Banned engineering testimony - B. Extended the Daubert reliability gate to non-scientist expert testimony, including engineers - C. Made engineers immune from cross-examination - D. Concerned bite marks

16. In a fire, cause arcing versus victim arcing is the distinction between: - A. Two brands of wire - B. Electrical activity that ignited the fire versus electrical damage produced by the fire - C. Arson and accident, always - D. Two investigators' opinions

17. The mere presence of melted wiring near a fire's origin: - A. Proves the fire was electrical - B. Is nearly worthless as a cause indicator alone (fire damages wiring regardless of origin); establishing an electrical cause requires distinguishing cause from victim arcing - C. Proves the fire was arson - D. Has no bearing on anything

18. Ruling out the electrical system as an accidental cause of a fire is, in the book's grammar: - A. An inclusion - B. An exclusion — the cleanest and strongest kind of statement forensic science makes - C. Proof of who set the fire - D. A class characteristic

19. Across the chapter's domains, the cleanest statement the evidence can usually make is: - A. "This one, and only this one, did it" - B. "Not this one" (exclusion) - C. "It is impossible to know anything" - D. "The expert is certain"

20. The deepest reason these domains belong in this book is that: - A. They involve crimes - B. The same evidentiary logic — class vs. individual, exclusion over proof, validity, bias — governs them as governs the homicide lab - C. They all use DNA - D. They are all about fire

Short answer

21. Explain why excluding a candidate source (of a species, a pollutant, or a failure cause) is generally a cleaner statement than attributing the evidence to a particular one. Connect to Chapter 1, §1.6.

22. A region-of-origin finding for seized ivory is, in the book's language, an "association with a place-type." Name one other piece of evidence from earlier in the book that is the same kind of claim, and give the honest verb both should use.

23. State, in two sentences, how a forensic engineer avoids the negative-corpus fallacy when concluding a cause — i.e., what a surviving hypothesis must rest on.

24. In the cold case, the fire was found incendiary on affirmative grounds (Chapter 22). Explain how this chapter's electrical-system exclusion complements that finding from the opposite direction, and what honest status the chapter delivers.

25. Write one sentence a chemist could honestly testify to about a spill's chemical pattern, and one sentence that would overstate it.

Answer key (click to expand) **Multiple choice:** 1-B · 2-B · 3-B · 4-B · 5-B · 6-B · 7-B · 8-B · 9-B · 10-B · 11-B · 12-B · 13-B · 14-B · 15-B · 16-B · 17-B · 18-B · 19-B · 20-B **Short answer (model points):** **21.** A single clear difference can *exclude*: if the species sequence, the chemical pattern, or the load calculation does not match what it would have to match, the candidate is ruled out, often conclusively. *Attribution*, by contrast, only ever says the candidate is *consistent with* the evidence, and its strength depends on how distinctive the match is and how many other candidates could share it — a probabilistic statement, not a certainty. This is the exclusion-over-proof asymmetry of Chapter 1, §1.6: a non-match closes a door cleanly; a match only narrows the hallway. **22.** The **pollen-on-the-floor-mat** evidence in the cold case (Chapter 13) — and more broadly soil comparison (Chapter 24) — is the same kind of *association with a place-type*. The honest verb for both is **"consistent with / supports"**, never "proves" or "individualizes the exact location." **23.** The engineer must reach the surviving hypothesis on *affirmative* physical evidence of its own — a measurable fatigue crack, a calculation showing the design was under-rated, a demonstrably defective weld — not merely on having eliminated the other branches. Eliminating other causes can *support* a hypothesis, but "I couldn't find anything else" is the negative-corpus fallacy and never, by itself, establishes a cause. **24.** Chapter 22 affirmatively established that the fire *was* deliberately set (multiple origins + ignitable-liquid pattern). This chapter affirmatively *closes the leading accidental alternative* by showing the electrical damage was fire-*caused* (victim arcing) with no competent ignition mechanism at the origin — i.e., *not* the electrical system. The two findings point at the same conclusion (staged-homicide fire) from opposite directions: one shows the fire *was* incendiary, the other shows it was *not* an electrical accident. Honest status: **accidental-cause alternatives closed** — with no person yet identified. **25.** **Honest:** "The chemical pattern recovered from the spill is consistent with, and — given the distinctiveness of its biomarker ratios relative to the other candidates sampled — supports attribution to source A; source B is excluded." **Overstated:** "The chemical fingerprint proves the spill came from source A and no other source on Earth."