OIC Forensic Science & Analysis 2 — Questions and Answers
Question 1: When documenting a fire scene, which evidence collection technique best preserves accelerant residues for laboratory analysis?
- Swab the surface with a dry cotton swab
- Place debris in an airtight metal can sealed with an adhesive lid (Correct answer)
- Collect samples in a paper bag to allow moisture evaporation
- Photograph only, as physical collection degrades accelerants
Correct answer: Place debris in an airtight metal can sealed with an adhesive lid
Airtight metal cans prevent accelerant vapors from escaping and contamination from entering, preserving volatile compounds for GC-MS analysis.
Question 2: In bloodstain pattern analysis, a 'satellite spatter' pattern is produced by:
- Blood dripping from a moving source
- Secondary droplets that break off from the primary droplet upon impact (Correct answer)
- Blood cast off from a swinging weapon
- Arterial spurts from a punctured blood vessel
Correct answer: Secondary droplets that break off from the primary droplet upon impact
Satellite spatters are smaller droplets ejected outward from the main bloodstain when the primary droplet strikes a surface.
Question 3: Which chemical reagent is used to develop latent fingerprints on porous surfaces such as paper?
- Luminol
- Ninhydrin (Correct answer)
- Sudan Black B
- Leuco Crystal Violet
Correct answer: Ninhydrin
Ninhydrin reacts with amino acids in sweat residue on porous surfaces, producing a purple compound called Ruhemann's purple.
Question 4: An Oregon inspector observes tool mark evidence on a door frame at a burglary scene. The FIRST priority should be to:
- Cast the tool mark immediately with dental stone
- Photograph the mark in place with a scale reference before any other action (Correct answer)
- Remove the section of door frame for lab submission
- Attempt to match the tool mark to tools found at the scene
Correct answer: Photograph the mark in place with a scale reference before any other action
Documentation through photography with a scale must occur before any physical handling to preserve the original condition of evidence.
Question 5: What does the term 'locard's exchange principle' mean in a forensic investigation context?
- Every crime scene must be photographed from multiple angles
- Whenever two objects contact each other, they exchange trace materials (Correct answer)
- All evidence must be exchanged between agencies for verification
- Physical evidence can be exchanged for witness testimony
Correct answer: Whenever two objects contact each other, they exchange trace materials
Locard's Exchange Principle states that every contact leaves a trace — the perpetrator brings something to the scene and takes something away.
Question 6: During a forensic entomology assessment, the presence of pupal casings but no live larvae at a decomposed body primarily indicates:
- The body was moved after death
- Adult flies have already emerged, suggesting a later postmortem interval stage (Correct answer)
- The scene is contaminated and evidence is unreliable
- Temperature data cannot be used to estimate time of death
Correct answer: Adult flies have already emerged, suggesting a later postmortem interval stage
Empty pupal casings indicate blowfly larvae have completed metamorphosis and adults have emerged, placing the death in a later stage of the PMI timeline.
Question 7: Which type of fingerprint is considered the most common ridge pattern found in the human population?
- Arch
- Loop (Correct answer)
- Whorl
- Tented arch
Correct answer: Loop
Loops comprise approximately 60–65% of all fingerprint patterns, making them the most frequently encountered ridge pattern.
OIC Forensic Science & Analysis 2
When documenting a fire scene, which evidence collection technique best preserves accelerant residues for laboratory analysis?