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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

  1. Which presumptive test is specifically used to identify the possible presence of seminal fluid based on the enzyme acid phosphatase?

    Answer: Brentamine Fast Blue test

    The Brentamine Fast Blue test detects acid phosphatase activity, which is present at high concentrations in seminal fluid.

  2. A trace examiner compares two paint chips using FTIR spectroscopy. What does FTIR primarily identify in paint evidence?

    Answer: The organic polymer binder and layer sequence

    FTIR identifies organic components like binder polymers (acrylic, alkyd, polyurethane) and their layer sequences in paint chip comparisons.

  3. In bloodstain pattern analysis, a low-velocity impact spatter is generally associated with stains of what approximate diameter?

    Answer: 3 mm or greater

    Low-velocity impact spatter typically produces larger stains of 3 mm or more because the blood drops travel slowly and spread less upon impact.

  4. When a questioned hair is examined microscopically, the medullary index is calculated. What is the typical medullary index for human hair?

    Answer: Less than 0.33

    Human hair typically has a medullary index less than 0.33, meaning the medulla diameter is less than one-third of the hair shaft diameter.

  5. Which of the following trace evidence types is most reliably analyzed using scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX)?

    Answer: Gunshot residue (GSR) particles

    SEM-EDX identifies the elemental composition (lead, barium, antimony) of GSR particles and characterizes their unique morphology.

  6. What distinguishes a transfer bloodstain from an impact spatter stain at a crime scene?

    Answer: Transfer stains result from direct contact with a bloody surface, while spatter results from a blood source being struck

    Transfer (contact) stains result from a bloody object touching a surface and leaving an impression, whereas spatter is created by force acting on a blood source.

  7. A criminalist recovers a questioned fiber with a smooth surface and circular cross-section that shows no birefringence under polarized light. This is most consistent with which fiber type?

    Answer: Glass fiber

    Glass fibers are isotropic and show no birefringence under polarized light, distinguishing them from most synthetic and natural textile fibers.