Chapter 14 — Self-Check Quiz

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

Multiple choice

1. A friction ridge pattern is best described as: - A. Constantly changing as a person ages, so it must be re-recorded periodically - B. Fixed for life (barring deep scarring), formed before birth, growing only in size - C. Determined entirely by genetics, so identical twins share identical prints - D. Present only on the fingertips

2. A latent print is: - A. A visible print left in blood or ink - B. A three-dimensional print pressed into a soft material - C. An invisible print left by skin residue, requiring development to be seen - D. A print taken deliberately on a ten-print card

3. A plastic print is: - A. A print on a plastic bag - B. A three-dimensional impression pressed into a soft, moldable material (putty, wax, caulk) - C. An invisible print developed with powder - D. A computer-generated print

4. Level 1 detail (overall pattern: loop/whorl/arch) can: - A. Identify a source to the exclusion of all others - B. Exclude a source, or narrow to a class, but never identify - C. Establish the time a print was deposited - D. Replace level 2 analysis entirely

5. The individualizing power of a fingerprint comparison lives mainly in: - A. Level 1 — the overall pattern - B. Level 2 — the minutiae and their configuration - C. The color of the print - D. The size of the fingertip

6. The most common fingerprint pattern family is the: - A. Arch - B. Whorl - C. Loop - D. Delta

7. "Galton points" is a historical name for: - A. The cores and deltas - B. The minutiae (ridge endings, bifurcations, etc.) - C. The three levels of detail - D. The AFIS candidate list

8. The correct method to develop latent prints on a porous surface such as paper is typically: - A. Magnetic powder - B. Ninhydrin (targets amino acids) - C. Small-particle reagent - D. Casting

9. Cyanoacrylate ("superglue") fuming is used because it: - A. Dissolves the background so the ridges stand out - B. Polymerizes onto residue components, forming a white cast that stabilizes a fragile print for further processing - C. Is the only method that works on paper - D. Destroys touch DNA, simplifying the case

10. The four steps of ACE-V are: - A. Acquire, Compare, Estimate, Verify - B. Analysis, Comparison, Evaluation, Verification - C. Analyze, Confirm, Establish, Validate - D. Assess, Catalog, Enter, View

11. In honest practice, the Analysis step of ACE-V should be completed and documented: - A. After the examiner has studied the suspect's exemplar - B. Before the examiner ever sees the comparison print - C. Only by the verifier - D. By the AFIS algorithm, not a human

12. The three permissible evaluation outcomes in ACE-V are: - A. Guilty, not guilty, undecided - B. Identification, exclusion, inconclusive - C. Match, near-match, no-match - D. Loop, whorl, arch

13. "Inconclusive" as an ACE-V outcome is: - A. A sign of examiner incompetence - B. An honest and common result when there is insufficient quality or quantity of detail to decide - C. Forbidden in accredited labs - D. The same thing as an exclusion

14. An AFIS search returns: - A. The name and photograph of the source - B. A definitive yes/no identification - C. A ranked candidate list of the most similar stored records, which a human must then examine - D. The latent's original depositor's address

15. When the true source of a latent has no record in any database, an AFIS search will: - A. Return "no source exists" - B. Refuse to produce a list - C. Still return its top several closest records, none of which is the source - D. Automatically flag the print as planted

16. The bias specific to working an AFIS candidate list is that: - A. The computer is always wrong - B. The list shows the records the system judged most similar, so a primed examiner may "see" agreement that is high-scoring coincidence - C. Lists are illegal in court - D. AFIS only searches one database

17. Blind verification means the second examiner: - A. Cannot see the prints - B. Re-examines without knowing the first examiner's conclusion - C. Is chosen at random from the public - D. Verifies only the pattern class

18. The 2016 PCAST report's conclusion about latent fingerprint comparison was that it is: - A. Fully discredited, like bite marks - B. "Foundationally valid" — studies show examiners can do the task at a measurable, usefully low, but non-zero error rate - C. As rigorous and quantified as single-source DNA - D. Without any scientific basis

19. In the Brandon Mayfield case, the print actually belonged to: - A. Mayfield - B. No one (it was a smudge) - C. Ouhnane Daoud, an Algerian national identified by Spanish police - D. An FBI examiner

20. The clearest lesson of the Mayfield case, per the chapter, is that: - A. Fingerprint ridges change over time - B. The equipment failed - C. A method can be valid in principle yet produce a confident, unanimous, catastrophic error when human interpretation is contaminated by context, priming, and non-blind verification - D. AFIS should never be used

Short answer

21. Explain, in two sentences, the difference between saying a finger's ridge detail is unique and saying an examiner can reliably distinguish a partial latent from an impression made by a different finger. Why does only the second have a measurable error rate?

22. Name the three bias entry points built into ACE-V as commonly practiced (per §14.4), and for each, state the safeguard in a phrase.

23. In the cold case, the gas-can latent came back inconclusive even though Keller was on the AFIS candidate list. Using §14.5 and §14.6, explain why a candidate-list appearance plus a loop-pattern consistency does not place his hand on the can.

24. Write one sentence a disciplined examiner could honestly say on the stand about a genuine 12-minutiae identification, and one sentence that would be a scientifically indefensible overstatement.

Answer key (click to expand) **Multiple choice:** 1-B · 2-C · 3-B · 4-B · 5-B · 6-C · 7-B · 8-B · 9-B · 10-B · 11-B · 12-B · 13-B · 14-C · 15-C · 16-B · 17-B · 18-B · 19-C · 20-C **Short answer (model points):** **21.** Uniqueness of the *source* is a claim about nature — that no two fingers' full ridge detail are identical, an empirical observation never falsified in over a century of comparison. Reliability of the *comparison* is a claim about people performing a task: how often an examiner, looking at a smeared, partial, distorted latent, confuses it for an impression from a *different* finger. Only the second is a task that can be tested under known ground truth, and only a task has a measurable, non-zero error rate; uniqueness, even if true, says nothing by itself about how often examiners err. **22.** (1) **Context at Analysis** — case facts ("he confessed," "terrorism case") shape which ambiguous features get counted; safeguard: **linear ACE-V**, complete and document the analysis of the latent before exposure to context or the exemplar (sequential unmasking). (2) **The reference print biases the analysis** — once you see the exemplar you cannot un-see it and may "find" in the latent the minutiae the exemplar told you to look for; safeguard: **analysis-before-comparison**, documented. (3) **Non-blind verification** — the verifier who knows the first conclusion is pushed toward agreement; safeguard: **blind verification** (the second examiner does not know the first's result). **23.** AFIS does not identify anyone; it returns a ranked candidate *list* of the records most similar to the latent, and that list *always* has a number one even when the true source is not enrolled. A loop is a level-1 (class) characteristic shared by roughly six in ten fingers on Earth, so "consistent with a loop" narrows to the majority of humanity and individualizes no one. The latent had insufficient quality and quantity of reliable level-2 minutiae to support an identification; "Keller is on the list" plus "the pattern is a loop" therefore does not — and cannot — place his hand on the can. To have declared it would be to repeat Madrid: a primed candidate plus a poor latent producing a false positive. **24.** **Honest:** "I conducted an ACE-V comparison and found agreement in pattern and in 12 minutiae in corresponding positions, with no differences I could not explain, and in my opinion the latent and the exemplar originated from the same source." **Overstated:** "This is the defendant's fingerprint, to the exclusion of every other person on Earth, with one hundred percent certainty and a zero error rate."