Fingerprints and Identification (lecture 12)

Fingerprints - Key Concepts

Biology of Fingerprints

  • Friction ridge skin on fingers, palms, and soles improves grip.
  • Patterns include ridges (hills) and valleys (furrows).
  • Each ridge has sweat pores, releasing sweat and oils that create a fingerprint impression.

Development and Uniqueness

  • Friction ridges form in the fetus and are persistent throughout life, except when scarred.
  • Ridge patterns are unique and vary within limits, coded genetically and influenced by fetal environment.

Levels of Detail in Fingerprints

  1. 1st Level: Basic patterns (e.g., plain whorl, central pocket loop).
  2. 2nd Level: Minutiae details (e.g., bifurcations, dot types) define individuality beyond general shapes.
  3. 3rd Level: Dimensional attributes (e.g., pore shape and size).

Automated Fingerprint Identification System (AFIS)

  • Utilizes algorithms to match prints from known individuals and evidence.
  • Requires qualified examiners to confirm matches.

Types of Fingerprints

  • Patent (visible)
  • Plastic (impressions)
  • Latent (not visible without processing)

Print Development and Comparison

  • Fingerprint residues composed of eccrine and apocrine sweat.
  • Various external factors influence fingerprint quality (sweating, diet, age, and sex).

Lifespan of Fingerprint Impressions

  • Affected by genetics, surface, and environment; cannot accurately gauge age without corroborative evidence.

Development Techniques for Fingerprints

  • Non-Porous Substrates: Use powders (magnetic/non-magnetic) or superglue fuming.
  • Porous Substrates: Require chemicals (e.g., ninhydrin) to visualize absorbed residues.

Fingerprint Identification Process

  • ACE-V Method: Analysis, Comparison, Evaluation, and Verification.
    • Focus on clarity, quality, and minutiae to validate identity.
  • No minimum points for a match established; relies on characteristics and context of comparison.