CPI Forensic Science & Analysis 2 — Questions and Answers
Question 1: When documenting accelerant burn patterns at a fire scene, which pattern most strongly suggests a liquid accelerant was poured in a trail?
- V-pattern on a wall
- Pour pattern or irregular low burn line on the floor (Correct answer)
- Alligatoring of wood surfaces
- Smoke staining above window openings
Correct answer: Pour pattern or irregular low burn line on the floor
A pour pattern or irregular low burn line on the floor indicates a liquid accelerant was distributed and ignited along that path.
Question 2: In forensic entomology used during death investigations, the presence of blow fly pupae but no adult flies indicates what about time of death?
- Death occurred within the past 24 hours
- Death occurred several days to weeks ago (Correct answer)
- The body was stored in a cold environment
- Insect activity is unrelated to time of death
Correct answer: Death occurred several days to weeks ago
Pupae represent a later development stage, suggesting death occurred days to weeks prior, as eggs hatch and larvae develop before pupation.
Question 3: A CPI inspector finds charring that is deepest at floor level with minimal ceiling damage. This pattern most suggests:
- The fire originated near the ceiling
- A rapid, high-energy flashover event
- A slow-burning, low-point fire origin possibly involving accelerants (Correct answer)
- Electrical arcing in the attic
Correct answer: A slow-burning, low-point fire origin possibly involving accelerants
Deep charring concentrated at floor level with limited ceiling involvement suggests a slow, low-burning fire, which may indicate an accelerant used at floor level.
Question 4: Which chemical test is commonly used in the field to presumptively identify the presence of blood at an inspection scene?
- Ninhydrin spray
- Luminol or Kastle-Meyer test (Correct answer)
- Iodine fuming
- Silver nitrate solution
Correct answer: Luminol or Kastle-Meyer test
Luminol (chemiluminescence) and the Kastle-Meyer test (phenolphthalein) are standard presumptive tests for blood detection.
Question 5: When analyzing a questioned document for ink dating, which laboratory technique examines the chemical degradation of ink over time?
- X-ray fluorescence (XRF)
- Thin-layer chromatography (TLC) (Correct answer)
- Scanning electron microscopy (SEM)
- Infrared spectroscopy of paper fibers
Correct answer: Thin-layer chromatography (TLC)
Thin-layer chromatography separates ink components to analyze their chemical composition and degradation, helping establish the approximate age of ink.
Question 6: A CPI inspector observes a distinctive 'low burn' pattern on door framing with clean burn marks near the floor. The most accurate interpretation is:
- Firefighters caused the damage during suppression
- This is consistent with arson using a floor-level accelerant (Correct answer)
- Natural gas leaked and pooled on the floor
- The pattern results from normal fuel load combustion
Correct answer: This is consistent with arson using a floor-level accelerant
Low burn patterns on vertical surfaces near floor level, especially with clean edges, are a classic forensic indicator of floor-applied accelerant use in arson.
Question 7: Which type of evidence is considered 'class evidence' rather than 'individual evidence' in forensic analysis?
- A fingerprint with 12 matching ridge characteristics
- DNA profile matching a single individual
- A shoe impression matching a brand and size but not a specific shoe (Correct answer)
- A bite mark matched to a specific individual's dentition
Correct answer: A shoe impression matching a brand and size but not a specific shoe
Class evidence links a sample to a group (e.g., shoe brand/size) but cannot be traced to a single unique source, unlike individual evidence.
CPI Forensic Science & Analysis 2
When documenting accelerant burn patterns at a fire scene, which pattern most strongly suggests a liquid accelerant was poured in a trail?