FINGERPRINTING

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FINGERPRINTING

• Everything you wanted to know and more!

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A BIT OF HISTORY

• 3,000 years ago the Chinese used fingerprints to
  sign legal documents.
• 1883 Alphonse Bertillon developed a system of
  body measurements to identify individuals instead
  of fingerprintsthis was used for 20 years.

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The Will West Case

• A man named Will West was
• arrested. His measurements
• were taken for identification,
• then he was told that he was
• already an inmate at the prison
• under the name William West.

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The Mug Shots
One is Will West, the other is William West They
claimed they werent related.
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The Fingerprints (West Case)

• Their fingerprints were very different.

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So Whats the Deal with the West Case?

• It was later determined that Will West
• and William West were identical twins.

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Three Fundamental PrinciplesFingerprints.

• Are an individual characteristic- no two have
  been found that are exactly identical.
• Remain unchanged during a persons lifetime.
• Have general characteristics that allow for
  classification.

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Individual Characteristics

• Ridge Patterns (aka minutae)- their number,
  identity, and relative location
• are unique to each person
• Experts make at least 12 points of comparison
  between prints to prove a match.

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Digital Print Comparison
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Prints Remain Unchanged

• Fingerprints are formed by the papillae, a layer
  of tissue found between the epidermis (outer
  layer of skin) and the dermis (inner layer of
  skin).

Papillae (wavy black line)
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Fingerprint Classification

• There are three basic categories

LOOP
WHORL
ARCH
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LOOPS

• 60-65 have loops
• Lines enter one side, loop around, and exit the
  same side.
• One delta (triangular pattern)

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WHORLS

• 30-35 Have whorls
• Rounded or circular pattern
• Two Deltas

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ARCHES

• 5 Have arches
• Lines enter from one side and exit the other.
• NO Deltas

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A FEW FINGERPRINT RIDGE CHARACTERISTICS
ISLAND
RIDGE ENDING
ENCLOSURE
BIFURCATION
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Prints At The Crime Scene

• Visible Prints - made by a finger stained with
  blood, food, paint, ink, etc.
• Plastic Prints - Prints pressed into a soft
  surface like clay, soap, or wax
• Latent Prints - Invisible prints left by body
  oils and greases

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LOCATING LATENT PRINTS

• For hard nonporous surfaces, such as glass,
  plastic, mirrors, tile, and painted wood- use
  dusting powder or Superglue fuming
• For soft, porous surfaces such as paper,
  cardboard and cloth- use Iodine fuming or other
  chemicals

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Methods for Locating Latent Prints
Dusting for Prints
Chemical Processing
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PRESERVING THE PRINT FOR EVIDENCE

• Always photograph the visualized latent print
  before further analysis for future comparison and
  evidence.

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LIFTING A DUSTED PRINT

• After dusting and photographing the print, a
  piece of tape (like Scotch tape) is placed over
  it. The pattern of the dusted print is
  transferred to the tape which is then mounted on
  a piece of contrasting colored cardboard.

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Printing methodswe will use in class

• Inking and classifying prints
• Dusting with powder lifting
• Superglue Fuming
• Iodine Fuming

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