Biological and Trace Evidence Flashcards
7 cards from real CSI practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Biological and Trace Evidence flashcards as text
Which of the following best describes the 'touch DNA' technique in forensic biology?
Answer: DNA extracted from sweat left by skin contact with an object
Touch DNA refers to epithelial cells shed from skin contact with surfaces, which can yield a low-template nuclear DNA profile.
A criminalist finds a fiber with a trilobal cross-section and a distinctive dye absorption spectrum. This cross-section is most associated with which common fiber type?
Answer: Nylon 6,6
Nylon 6,6 fibers are commonly manufactured with a trilobal cross-section to improve texture and luster.
When documenting a pooled bloodstain, what measurement is recorded to help reconstruct the event?
Answer: The area, shape, and perimeter characteristics of the pool
Area, shape, and perimeter features of a pooled bloodstain document the extent and behavior of the deposit for reconstruction purposes.
Which type of evidence packaging is most appropriate for moist biological samples to prevent mold and DNA degradation?
Answer: Paper bag or envelope after air drying the sample
Biological evidence should be air-dried before packaging in paper, which allows moisture to escape and prevents microbial degradation of DNA.
In entomological evidence, the succession of insect species on a body can help estimate the postmortem interval (PMI). Which insect family is typically FIRST to colonize remains?
Answer: Calliphoridae (blow flies)
Blow flies (Calliphoridae) are usually the first colonizers of remains, arriving within minutes to hours of death to deposit eggs.
What is the purpose of a substrate control when collecting a biological stain from a surface?
Answer: To collect background material from an unstained area for comparison
A substrate control is collected from an adjacent unstained area to identify any background chemicals or DNA that could interfere with analysis.
Glass refractive index (RI) is measured in forensic comparisons. Which instrument is the gold standard for measuring glass RI?
Answer: GRIM3 (Glass Refractive Index Measurement) system
The GRIM3 system uses the phase contrast/Becke line method to precisely measure glass refractive index for forensic comparisons.