ETC Trace Evidence 1 — Questions and Answers
Question 1: Which principle forms the scientific foundation for trace evidence and states that every contact leaves a trace?
- Daubert Standard
- Frye Standard
- Locard's Exchange Principle (Correct answer)
- Bertillon Identification System
Correct answer: Locard's Exchange Principle
Locard's Exchange Principle holds that whenever two objects come into contact, material is transferred between them, forming the basis for all trace evidence analysis.
Question 2: Which type of microscope is most commonly used by forensic analysts to directly compare hair and fiber evidence side by side?
- Scanning electron microscope
- Phase contrast microscope
- Fluorescence microscope
- Comparison microscope (Correct answer)
Correct answer: Comparison microscope
A comparison microscope links two separate microscopes optically, allowing an examiner to view a questioned sample and a known sample simultaneously in a split field of view.
Question 3: What physical property of glass fragments is measured to help determine whether two samples share a common origin?
- Tensile strength
- Surface hardness (Mohs scale)
- Refractive index (Correct answer)
- Thermal conductivity
Correct answer: Refractive index
Refractive index measures how much light bends when passing through glass and is highly consistent within a single production batch, making it a key comparison value.
Question 4: What is the primary limitation of microscopic hair comparison as standalone forensic evidence?
- Hair degrades too quickly to be useful
- It cannot be performed without DNA testing
- It cannot provide the individualization to a single source that DNA can (Correct answer)
- It requires equipment unavailable in most crime labs
Correct answer: It cannot provide the individualization to a single source that DNA can
Microscopic hair comparison is class-characteristic analysis and cannot definitively identify a single individual as the source; DNA analysis of the hair root or shaft is required for individualization.
Question 5: How should trace evidence such as loose fibers or hair be packaged at the crime scene to prevent loss?
- In sealed plastic zip-lock bags
- In paper envelopes or using a druggist fold (Correct answer)
- Loose inside a standard evidence box
- In glass vials submerged in saline
Correct answer: In paper envelopes or using a druggist fold
Paper envelopes and druggist folds allow moisture to escape (preventing mold) while securely containing small loose particles without static buildup that plastic bags can cause.
Question 6: A tape lift is used at a crime scene primarily to:
- Develop latent fingerprints on smooth surfaces
- Collect loose hair, fibers, and small particles from surfaces (Correct answer)
- Preserve shoeprint impressions in soft soil
- Stabilize bloodstain patterns for transport
Correct answer: Collect loose hair, fibers, and small particles from surfaces
Tape lifts use the adhesive surface of clear tape pressed against clothing, seats, or other surfaces to capture loose trace materials that can then be examined microscopically.
Question 7: Which type of transfer involves trace evidence moving from the original source to a secondary surface through an intermediary object or person?
- Direct transfer
- Reciprocal transfer
- Primary transfer
- Secondary transfer (Correct answer)
Correct answer: Secondary transfer
Secondary transfer occurs when trace material moves from surface A to surface B, and then from B to surface C — meaning the final recipient never had direct contact with the original source.
ETC Trace Evidence 1
Which principle forms the scientific foundation for trace evidence and states that every contact leaves a trace?