Chapter 2 Exercises: The Crime Scene

Work these in order; they move from recall to applied reasoning to ethics and scene interpretation. Items marked with a dagger (†) have worked solutions in the answers appendix. There are no answers in this file — that is deliberate. Reason first.

A note on tone: several items ask you to "spot the overstatement" or to decide what a scene does and does not establish. The point is never to memorize a procedure but to build the habit this book is about — claiming exactly as much as the evidence supports, and no more.

A. Recall and definitions

  1. Define crime scene in a single sentence, and explain why the definition contains two uses of the word "may."
  2. List the first responder's four duties in priority order, and state what outranks every evidentiary concern.
  3. † What is scene security, and name the single most useful piece of paper involved in maintaining it?
  4. Name the three independent records that document a scene, and give one thing each captures that the other two cannot.
  5. State the rule of sequence that governs all documentation in eight words or fewer.
  6. † Define chain of custody. What single question is it a written answer to?
  7. Distinguish a primary scene from a secondary scene with one example of each.
  8. What does "paper for biology, plastic for the rest" mean, and why is it true?
  9. Name four search patterns and state the scene each is best suited to.
  10. What is a substrate control, and why must it be collected at the scene rather than later?

B. Applied reasoning

  1. A detective collects a knife from the floor, then realizes the scale was left in the truck and the knife is already bagged. List, in order, the documentation steps that were skipped, and state exactly what information is now unrecoverable.
  2. † An officer arrives first at a remote cabin fire, confirms the occupant is dead, and exits the unstable structure. A neighbor, three other firefighters, and a grieving relative all approach the cabin over the next twenty minutes. No log is kept. Identify every scene error already committed before any evidence is touched, and rank them by how much each will damage the case.
  3. Two swabs are taken of the same wet bloodstain. Swab A is air-dried and sealed in paper; Swab B is sealed wet in a zip-top bag "so it won't leak." Nine warm days later they reach the lab. Predict each swab's outcome and explain the mechanism in terms of what destroys DNA.
  4. You must search the ground around an outdoor scene for a discarded weapon, with six searchers. Choose a search pattern, justify the choice, and explain how you would record that the whole area was covered.
  5. † A body is found face-down, but livor mortis (settled blood) has pooled along the back. What does this single observation tell you about the scene, and what does it not yet tell you?
  6. An item arrives at the lab logged out of the property room at 09:12 and logged in at the lab at 14:40, with no account of the intervening time. The seal is intact. Is this a problem? What is the defense's argument, and what is it not able to argue?
  7. Explain why setting the perimeter "farther out than feels necessary" is sound practice, using the idea of the perpetrator's route.
  8. A scene is searched once, quickly, by a team confident it is "just an overdose." Name two distinct mechanisms from this chapter by which that confidence could cause real evidence to go uncollected.

C. Evidence interpretation

  1. † You are handed a crime-scene photograph of a bloodstain with no scale in the frame and no accompanying sketch. State precisely what you can and cannot conclude from it, using honest forensic verbs.
  2. A rough sketch records a gas can at 1.40 m from the west wall and 0.90 m from the north wall; a photograph seems to show it closer to the body. The cabin has since been demolished. Which record governs the can's position, and why does it survive the demolition?
  3. A "suicide" scene shows a gunshot wound, but the deceased's hands test negative for gunshot residue and the wound is in a location the person could not physically have reached. Name the kind of scene this is and the single principle by which it is detected.
  4. † A perfectly documented swab — full photographs, measured sketch, flawless chain of custody — yields a DNA profile, but the collector used the same gloves across five items before bagging it. Evaluate the result. What is the chain of custody worth here, and what is it powerless to fix?
  5. An investigator reports that, based on how the scene was "arranged," the offender was "an organized, controlling personality who knew the victim." Separate the part of this claim that the physical evidence might support from the part that is overreach, and name the chapter that deflates the overreaching part.

D. Spot the overstatement

  1. † A report states: "The unbroken chain of custody proves the evidence is reliable." Rewrite the sentence so it claims only what a chain of custody actually establishes.
  2. A prosecutor tells the jury: "The crime-scene technician is a trained professional, so we can trust that everything at the scene was collected correctly." Identify the unstated assumption and explain why professionalism alone does not establish correct collection.
  3. An investigator testifies: "We found no forensic evidence pointing away from the defendant." Explain why "we found no evidence" is a claim that depends entirely on how the scene was searched, and what question the defense should ask next.

E. Ethics and judgment

  1. A paramedic, saving a life, moves a body and cuts away clothing, badly disturbing the scene. Was this an error? Frame the correct rule, and explain the one thing the paramedic must do to convert an unavoidable disturbance into usable information.
  2. † A supervisor under time and political pressure tells you to downgrade an ambiguous death scene to "accidental" before the search is complete, to free up the team. Lay out the forensic argument for refusing, in terms of irreversibility and the validity of everything downstream.
  3. You discover, midway through processing, that a colleague handled three items with bare hands an hour ago. What is your obligation regarding documentation and disclosure, and why is hiding the lapse worse than the lapse itself?

F. Cold-case extension

  1. † (Mill Creek) Reread this chapter's Case File. Write the one-paragraph entry you would place at the top of the Mill Creek file describing the condition of the scene work — not who is guilty, but how trustworthy the foundation is. Use at least four specific scene-processing standards from this chapter, and state honestly what this entry does and does not add to the investigation.
  2. (Mill Creek) The cabin is treated early as the place the whole event happened. Argue, using §2.6, why an investigator should hold open the possibility that it is a secondary scene, and name one future chapter whose evidence will help decide.
  3. (Mill Creek) List, in collection order, the items the Case File says the cabin held (gas can, charred documents, tools, the door, the phone, a stray cartridge case) and assign each a correct packaging choice and one reason, flagging which item's packaging error would be most catastrophic and why.

G. Synthesis and transfer

  1. In one paragraph, defend the claim that "the case is usually won or lost at the scene" to a skeptic who believes the laboratory is where forensic science really happens.
  2. † Explain how three of the eight common scene errors in §2.7 can all trace back to a single root cause, and name that cause.
  3. Connect this chapter to Chapter 1's theme that forensic science "excludes more than it proves": why does the exclusion power specifically depend on good scene work, and what happens to it when the scene is contaminated?
  4. Write a five-line checklist a first responder could keep in a pocket that, if followed, would prevent the four most damaging errors in §2.7.
  5. A juror asks why real forensic work involves "so much paperwork." Answer in two sentences that connect documentation and chain of custody to the trustworthiness of the eventual science.
  6. † Construct a short scenario (4–6 sentences) of a scene processed correctly in every respect, and annotate each correct action with the section of this chapter that justifies it.