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Fingerprinting

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Fingerprinting Fingerprinting Why do we have fingerprints at all? Thicker skin than the rest of the body on hands and feet Lots of sweat pores to aid further friction ... – PowerPoint PPT presentation

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Title: Fingerprinting


1
Fingerprinting
2
Why do we have fingerprints at all?
  • Thicker skin than the rest of the body on hands
    and feet
  • Lots of sweat pores to aid further friction

3
What gives us our fingerprints?
  • Tough outer layer epidermis
  • (protects the inner layer)
  • Delicate inner layer dermis
  • (contains sweat glands, nerves and unique ridge
    pattern detail)
  • If the epidermis is injured (and not the dermis)
    no scarring will take place
  • If the dermis is injured a permanent scar will
    result (irreversibly disrupting the flow of ridge
    detail)

4
Classifying fingerprints
Double loop
Central -pocket loop
Loop
Plain arch
Plain whorl
Tented arch
5
Why do we leave finger prints everywhere?
  • The surfaces of the friction ridges on the hands
    and feet are covered in a constant film of-
  • Perspiration
  • Oil
  • Foreign substances acquired through contact with
    objects
  • These substances are then transferred to the
    objects we touch in the unique pattern of our
    fingers.

6
Finger prints are unique
The friction skin on the hands and feet is
formed in the 4th foetal month and does not
change (except through injury or
disease) Duplication doesnt happen in nature
even identical twins with the same DNA will have
different fingerprints
7
Fingerprint Detection
  • Finger prints at a crime scene can be
  • patent/legible clearly visible with the naked
    eye
  • impressed 3D marks in clay, soap or other soft
    material
  • latent hidden and must be revealed using
    chemicals or special lights

Methods for revealing latent fingerprints target
one or more of the ingredients of the residue
commonly found on fingers. E.g. dusting powder
adheres to anything sticky such as oil water on
non-absorbent surfaces (plastic,glass) (doesnt
always detect older fingerprints as the residue
will not stay sticky for long)
8
  • Who Dunnit?
  • In fours-
  • 1 latent print dusted and lifted for examination
    from crime scene
  • 4 sets of suspects prints for comparison to
    crime scene print done using ink
  • Give your set of prints to another group for them
    to decide Who Dunnit!!!!

9
Homework Task Research a method used at crime
scenes to reveal latent finger prints, other than
using powder dusting. Either prepare a A4
handout or PowerPoint (2-3 slides) to be given
out to the rest of the group, summarising your
findings.
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