Fingerprints

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Fingerprints
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Background Information

• Each fingerprint is made up of friction ridges,
  that do not change over time (unless scarring
  occurs)
• Fingerprints are formed in the womb
• Each fingerprint is a deposit of wastes when a
  person comes in contact with a surface
• 98 is water salts, 1 oils, 1 amino acids

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Prints at a Crime Scene

• Divided into 3 types
• Patent Print
• Plastic Print
• Latent Print

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Patent Print

• Can be seen with the naked eye
• Made by a hand that had blood, grease, oil, or
  any other sticky substance on it

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Plastic Print

• Visible to the naked eye
• Formed when an impression is made in a soft
  substance such as putty, glue, dust, or butter

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Latent Print

• Most common type
• Cannot be seen without applying powder or
  chemicals
• Substances adhere to the amino acids or oils in
  the fingerprint and make it visible

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Patterns of Fingerprints

• 3 basic types of patterns
• Arch 5 of population
• Loop 65 of population
• Whorl 30 of population

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Basic Fingerprints
ARCH LOOP WHORL
Plain Arch Left Radial Loop Plain Whorl
Tented Arch Left Ulnar Loop Central Loop Whorl
Right Radial Loop Double Loop Whorl
Right Ulnar Loop Accidental Whorl
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The Arch

• Formed when the ridge lines go from one side,
  rises in the middle, and leaves on the other side
  (like a wave)
• Tented arches are more pointed
• No ridgecount

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Example of Arch
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The Loop

• Ridge lines enters exits on the same side of
  the finger
• Type is determined by the direction the ridges
  come leaves
• If it is from the thumb-side of the finger, it is
  called a RADIAL LOOP
• If it is from the little finger side it is called
  an ULNAR LOOP

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Examples of Loops
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The Delta

• Whorls are subdivided using a ridge
  characteristic called a DELTA
• DELTA Triangle pattern (ridge forks nearby
  ridge)
• Whorls have 2 deltas, loops have 1 delta arches
  have 0 deltas

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The Whorl
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Ridge Characteristics

• BIFURCATION (or fork) ridge splits into 2
  friction ridges
• ENCLOSURE forms an oval
• ENDING RIDGES ridges that stop abruptly

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Ridge Characteristics Continued

• SHORT RIDGES begin end abruptly, traveling a
  short distance
• RIDGE DOT isolated ridge thats length is
  approximately its width

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Examples of Ridge Characteristics
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Identifying Fingerprints

• 8-12 points of comparison must be in common to
  declare the 2 prints a match
• When a partial print is available, as many
  characteristics must be matched as possible
• Characteristics can be matched to the AFIS
  (Automated Fingerprint Identification System)

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Example of Positive ID
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