Chapter 5 — Exercises

Work these in order; they climb from recall to applied reasoning to ethics. Items marked with a dagger (†) have worked solutions in the answers appendix. No answers appear in this file — wrestle with each before you check. Several items ask you to apply the four Daubert factors; keep them in front of you: testability, error rate, peer review, general acceptance.

A. Recall and definitions

  1. Define the Frye standard in one sentence, naming the single question it asks of a method.

  2. † Define the Daubert standard in one sentence, and state how the judge's role under it differs from the judge's role under Frye.

  3. What is FRE 702, and what does the post-2000 version of it require beyond "a qualified expert may give an opinion"?

  4. In Daubert, the judge is called the gatekeeper. Gatekeeping between what and what? Be precise about what the judge is and is not deciding.

  5. List the four classic Daubert factors from memory.

  6. † Define error rate as the chapter uses it. Why does "we have never had a case overturned" fail to state one?

  7. What does peer review mean in this context, and what does its absence tell you about a method?

  8. State the holding of Kumho Tire in one sentence.

  9. Name the three decisions usually grouped as the "Daubert trilogy."

  10. Which standard — Frye or Daubert — is older, and roughly what years did each govern federal courts?

B. Comprehension and contrast

  1. The chapter argues courts and laboratories are "two different truth-finding systems." List the four differences it draws (clock, goal, standard of proof, posture toward authority) and give a one-line example of each.

  2. † Explain the circularity built into the Frye standard, using a forensic method as your example. Why is this circularity "almost perfectly designed" to admit old junk science?

  3. Daubert is described as, in principle, more demanding than Frye in two opposite directions. Name both directions (what it can now exclude that Frye couldn't; what it can now admit that Frye couldn't).

  4. Explain why the chapter calls the four Daubert factors "the scientific method itself, written down as a legal test." Match each factor to the scientific practice it encodes.

  5. Why did the pattern-comparison disciplines try to argue, after Daubert, that their work was "skill, not science"? What were they hoping to gain, and how did Kumho Tire foreclose it?

  6. † The chapter says general acceptance was "demoted" by Daubert, not discarded. Demoted from what to what? Why does it argue the demotion often fails in practice?

  7. Distinguish a method's foundational validity from the reliable application of that method in a specific case. Which prong of amended FRE 702 covers the second, and why is it the more neglected?

  8. Explain the "grandfather" problem in your own words. Why does a method's long courtroom history function, perversely, as an argument for its admission rather than against it?

C. Applying the Daubert factors

  1. † A prosecutor offers testimony that two toolmarks were made by the same pry bar, based on the examiner's twenty years of experience and the fact that "every examiner in the lab agreed." Run all four Daubert factors against this offer. Which does it satisfy, and which does it dodge?

  2. Run single-source nuclear DNA typing through the four factors. Show why it clears all four, and name the one place in the process (not the method) where it could still produce a wrong result.

  3. A defense attorney challenges a bite-mark identification offered against her client. Draft the four questions she should ask the odontologist on cross, one per Daubert factor. For each, state what answer would expose the method's weakness.

  4. † A new method — call it "thermal-trace voiceprinting" — appears in court for the first time, has been published in two peer-reviewed journals, reports a measured error rate from blind studies, but is not yet generally accepted because it is so new. Under Frye, is it admissible? Under Daubert? Explain what this contrast reveals about the two standards.

  5. Take the chapter's three-pile sort of the Cold Case evidence (clears an honest gate / admissible but contestable / should not survive). Place each of the following into a pile and name its weakest Daubert factor: (a) GC-MS confirmation of gasoline; (b) a fire investigator's "pour pattern" opinion offered without lab confirmation; (c) a partial latent fingerprint; (d) soil on a boot "consistent with" the scene.

  6. A method satisfies general acceptance strongly but fails testability and has no error rate. The judge admits it. State, in one sentence each, (a) what the judge did wrong under the factors, and (b) why a juror who trusts "the judge let it in" will be misled.

D. Evidence interpretation and "spot the overstatement"

  1. † A forensic witness testifies: "This method is scientifically reliable; it has been admitted in courts across the country for over fifty years." Identify the logical move being made and name the chapter concept it illustrates. Why is the sentence's truth irrelevant to the method's validity?

  2. Rewrite this overstated sentence so that it claims only what an honest examiner could defend: "My examination proves the fire was arson; the pour patterns leave no doubt." (Assume no instrumental confirmation has been done.)

  3. A trial judge writes: "The defense's concerns about this method go to its weight, not its admissibility; the jury can sort it out on cross-examination." Quote the Justice Blackmun epigraph that endorses this reasoning, then explain — using the CSI effect from Chapter 1 — why "let the jury weigh it" can fail badly for weak forensic evidence.

  4. † An examiner says, on cross, "Our discipline's error rate is essentially zero — I've never been shown to be wrong." Explain the two distinct errors packed into that sentence (one about what an error rate is, one about what "never been shown" can hide).

  5. Identify which Daubert factor each of these phrases is really (or falsely) addressing: (a) "It's been peer-reviewed and published." (b) "Everyone in my field does it this way." (c) "We ran blind proficiency tests and missed 1 in 50." (d) "There's no experiment that could show me wrong — I just see the match."

E. Reasoning about the two systems

  1. The chapter claims the law's mechanism for self-correction is "far weaker" than science's. Defend this claim with two concrete contrasts (what happens to a wrong scientific belief vs. a wrongful conviction).

  2. † Why does it matter that "beyond a reasonable doubt" and "preponderance of the evidence" are verbal standards that courts resist turning into numbers, given that much forensic testimony is at bottom a probability claim? (You will meet this collision in full in Chapter 9 — answer from this chapter's setup.)

  3. The chapter notes that Daubert is applied more aggressively against civil plaintiffs than against the forensic evidence offered against criminal defendants. State this asymmetry precisely, and explain why it is the chapter's "bitter irony."

F. Ethics and judgment

  1. The chapter insists the Willingham fire investigators "were not frauds." Why does it make a point of this, and why is sincere belief in an unvalidated method described as more dangerous, not less, than deliberate fraud? Connect your answer to the Cognitive-Bias Watch callout.

  2. † You are a lab analyst asked to testify that a pattern method "individualizes" a mark to your suspect, using language your supervisor and your field accept — but you know the method has no published error rate. Walk through the ethical tension using this chapter's concepts. What can you honestly say on the stand, and what must you refuse to say?

  3. A defense attorney could file a Daubert challenge to weak forensic evidence but knows the local court reliably admits it anyway and the motion will cost her client money and delay. Argue both sides of whether she should file it. What does the "grandfather" problem do to her odds?

G. Cold Case extension

  1. † Return to your Cold Case evidence log and add the admissibility column the Case File asked for. For each evidence type the book will eventually develop (DNA from the gas can, GC-MS accelerant confirmation, the fire-origin determination, a fingerprint, soil/pollen, the autopsy findings), record (a) which of the three admissibility piles it falls in and (b) its single weakest Daubert factor. Then write one sentence on why the fire evidence is the entry that most demands caution in this particular case.

  2. A detective on the Mill Creek case wants to call the fire "obvious arson" based on "crazed glass and burn patterns on the floor," before any lab work. Using this chapter and the Case File, write the two-sentence response you would give: what the science can support now, and what valid path an arson finding must actually take (previewing Chapter 22).

  3. Suppose, hypothetically, that an early investigator had built the entire Mill Creek theory on Willingham-style fire indicators and a confident profile of one suspect. Which one suspect from the frozen cast is the book's designated near-miss wrongful conviction, and what would it have meant for him if a generalist court had admitted that folklore unchallenged? (Name the risk; do not invent the solution.)

  4. The Cold Case lab is small and under-resourced (Chapter 4). Explain how a weak local Daubert gate and a weak local lab compound each other: how does each make the other's failures more likely to reach a jury? (Preview the reform argument of Chapter 38.)

  5. † Write the one-paragraph "admissibility brief" you would hand a prosecutor preparing the Mill Creek case: which evidence threads will hold weight in court, which will be fought over, and which should never be offered — and why offering the last category would not just be weak but dangerous, given what this chapter taught about the gate.