fingermarks and powder visualisation

• what are they

  impressions of ridges
• explain structure

  arches

  loops

  whorls
• types of fingerprints

  patent visible

  latent invisible
• brushes

  natural (squirrel) granular powders eg carbon black, white, fluorescent

  magnetic

  synthetic (glass, fibre, zephyr) flake powders eg aluminium, bronze, gold
• health and safety

  wear mask

  ventilation

  aware of exposure limit
• powder enhancement

  use dry, clean, smooth non porous surfaces
• example

  iso17025
• recovery

  photograph if ridges are visible

  lift either by taping (for flake powders) or gelatine (for granular powders, use an acetate sheet)

  record

  retain
• levels

  1. pattern
  2. minutiae
  3. pores
• constituents of a fingerprint

  sweat gland

  sebaceous gland (fatty acids, glycerides, waxy esters, cholesterol)
• positive patent


  material from finger to surface
• negative


  material from surface to finger