Trace Evidence Flashcards
7 cards from real ETC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Trace Evidence flashcards as text
What is cross-contamination in the context of trace evidence collection?
Answer: Transfer of material between unrelated samples during collection or analysis
Cross-contamination occurs when trace material from one sample inadvertently transfers to another, potentially creating false associations and compromising the evidentiary value of both samples.
Paint transfer evidence from a hit-and-run scene is best characterized using which combination of analytical methods?
Answer: FTIR spectroscopy and scanning electron microscopy with EDX (SEM-EDX)
FTIR identifies the organic binder and pigment chemistry of paint layers, while SEM-EDX provides elemental composition of inorganic pigments, together allowing detailed layer-by-layer comparisons.
What is the forensic significance of finding bi-directional trace evidence transfer between two individuals?
Answer: It strongly suggests direct physical contact between the two individuals
Mutual exchange of trace materials — where each person's fibers or hair are found on the other — is highly consistent with direct physical contact and is difficult to explain through secondary transfer alone.
When collecting fire debris from an arson scene for accelerant analysis, what type of container should be used?
Answer: Airtight metal cans or heat-sealed nylon bags
Airtight metal cans or nylon bags trap volatile accelerant vapors that would otherwise evaporate, preserving them for headspace analysis and gas chromatography/mass spectrometry.
Which microscopic feature of hair is used by forensic analysts to estimate the racial ancestry of the contributor?
Answer: Cross-sectional shape and distribution of melanin pigment granules
Cross-sectional shape (round, oval, or triangular) combined with pigment granule distribution (clumped vs. evenly distributed) are the primary features used to estimate racial ancestry, though this analysis has limitations.
How should an evidence technician handle clothing items suspected to contain trace evidence?
Answer: Package each item separately in paper bags and avoid shaking or folding unnecessarily
Separate paper packaging prevents cross-contamination between items, and minimizing manipulation preserves loosely attached trace materials that might otherwise dislodge and be lost.
What is the primary forensic value of botanical trace evidence such as pollen grains, seeds, or plant fragments?
Answer: Can associate a person, object, or vehicle with a specific geographic location or environment
Pollen, spores, and plant fragments are often geographically specific, allowing forensic botanists to link a suspect, victim, or item to a particular location or environment where those plants grow.