Forensics Final Exam Study Guide Notes

Scenario Overview

  • Scenario: Museum break-in with a stolen artifact.
  • Evidence: Broken window, footprints, torn cloth fibers, and hair strands. No security footage is available.

Section I: Multiple Choice – Review Topics

  • Crime Scene Protocol
    • First step: Secure the scene to preserve evidence and prevent contamination.
  • Hair Analysis
    • DNA is found in the root of the hair.
    • Analyze medulla pattern, pigment, and cuticle under a microscope—not DNA sequencing.
    • Human hair typically has a medullary index < 1/3. That is, medullary\ index < \frac{1}{3}.
  • Fiber Types
    • Natural fibers: Cotton, wool, etc.
    • Synthetic fibers: Polyester, nylon, acrylic (man-made).
    • Collect fibers with tape lifting for small areas.
  • Evidence Classification
    • Trace evidence: Small, often transferred (hair, fiber, glass).
    • Class evidence: Shared by a group (e.g., fiber type, hair color).
    • Individual evidence: Unique to one person (e.g., DNA, fingerprints).
  • Chain of Custody
    • Ensures evidence is tracked and unaltered.
    • Prevents contamination or tampering.
  • Microscopy
    • Comparison microscope is best for analyzing fibers side-by-side.

Section II: True or False – Clarifications

  • Hair with medullary\ index < \frac{1}{3} = human.
  • A single hair cannot definitively identify someone unless it has DNA.
  • Cortex = contains pigment.
  • Cross-contamination occurs if gloves aren't changed.
  • Mitochondrial DNA = traces maternal lineage.
  • Always document before packaging evidence.
  • Not all crime scene sketches are perfectly to scale—but they should include dimensions.
  • Synthetic fibers are man-made; not all fibers are synthetic.

Section III: Short Answer – Key Concepts

  • Chain of Custody
    • Must be carefully documented.
    • Broken chain = evidence could be inadmissible in court.
  • Museum Physical Evidence
    • Hair strands: Can connect a suspect via class or mitochondrial DNA.
    • Fibers: Match to suspect clothing.
    • Footprints: Link to shoe type or wear pattern.
  • Class vs. Individual Evidence
    • Class: Hair color, fiber type—shared by group.
    • Individual: DNA in root, fingerprint—unique to one person.
  • Collecting Fiber Evidence
    • Use forceps or tape lift.
    • Store in paper bindles or envelopes.
    • Label and log in chain of custody.
  • Hair Analysis without Root
    • Use mitochondrial DNA (from mother).
    • Compare physical characteristics (medulla, pigment).
  • Crime Scene Documentation Steps
    • Secure the scene.
    • Take photographs.
    • Make sketches.
    • Record notes.
    • Label and number evidence before collecting.

Section IV: Quantitative/Analytical – Interpreting Evidence

  • Medullary Index
    • Hair A (0.28) is likely human.
    • Hair B (0.55) suggests animal origin.
  • Fiber Classification
    • Fiber X: Melts, uniform → Synthetic.
    • Fiber Y: Burns like paper, irregular → Natural.
  • DNA from Hair A
    • No root = no nuclear DNA.
    • Can use mitochondrial DNA (inherited from mother).
  • Hair Evidence Value
    • Match in medullary index & pigment = class evidence.
    • Helpful for placing someone at the scene—not enough to convict without more proof (e.g., DNA, fingerprints).

Study Tips

  • Review vocabulary: cuticle, cortex, medulla, chain of custody, trace evidence.
  • Practice evidence analysis scenarios.
  • Be able to explain steps of crime scene investigation.
  • Review microscope images of hair and fibers.