Fingerprints

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Fingerprints

• Chapter 14
• Criminalistics

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History of Fingerprinting

• First systematic attempt at personal
  identification
• Alphonse Bertillon in 1883
• Anthropometry system of precise body
  measurements
• Included detailed descriptions of the subject
• Full-length and profile photographs
• Accuracy of measurements were disproved by the
  William West Case

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History of Fingerprinting

• Francis Galton
• 1892 Published Finger Prints
• Described the anatomy of fingerprints and
  suggested methods for recording them
• Acknowledged that no two prints are alike and do
  not change throughout a lifetime
• Three pattern types
• Loops, Arches, and Whorls

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Fundamental Principles of Fingerprints

• First Principle
• A fingerprint is an individual characteristic.
  No two fingers have yet been found to possess
  identical ridge characteristics
• Individuality of a fingerprint is not determined
  by its general shape or pattern but by careful
  study of ridge characteristics or minutiae
• Examples bifurcation, enclosures, islands,
  ridge endings, short ridges, ridge crossings,
  deltas

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Figure 14-1
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Figure 14-2
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Fundamental Principles of Fingerprints

• Second Principle
• Fingerprints have been designed by nature to
  increase grasp and to resist slippage and are
  formed in the fetal stage of development.
• Fingerprints are formed by
• Hills (Ridges) raised portions of the epidermis
• Valleys (Grooves) lowered portions of the
  epidermis
• IT IS THE RIDGES THAT ARE INKED WHEN FINGERPRINTS
  ARE TAKEN

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How are Fingerprints Formed?

• The Dermal Papillae is the boundary between the
  epidermis (outer skin) and the dermis (inner
  skin).
• The shape of this boundary is wavy. This wave
  pattern determines the pattern of the fingerprint
  and remains unchanged throughout your lifetime.

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Leaving Your Mark

• Skin ridges have a single row of pores that open
  from the sweat glands.
• Perspiration is discharged through the pores and
  oils from the body collect in the ridges and
  valleys.
• Impressions from the fingertips are transferred
  onto a surface, leaving a fingerprint.
• Latent fingerprints are deposited in this manner
  and cannot be seen with the naked eye.

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Fundamental Principles of Fingerprints

• Third Principle
• Fingerprints have general ridge patterns that
  permit them to systematically classified.

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Taking Fingerprints

• Fingers are rolled in ink left-to-right, careful
  not to adhere too much ink to the fingertips
• The fingertips are then rolled left-to-right on a
  Ten-Print Card in the appropriate place for each
  finger
• A straight down print is then taken for each of
  the four fingers simultaneously and for each
  thumb and recorded on the Ten-Print Card

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This is the original Ten-Print Card of Rosa Parks
after the Montgomery Bus Boycott
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Three Classes of Fingerprints

• Loops, Whorls, and Arches
• Loops 65 of worlds population
• Whorls 30-35 of worlds population
• Arches 5 of worlds population

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Loop Patterns

• One or more ridges entering from one side of the
  print, recurving, and exiting from the same side

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Types of Loop Patterns

• Ulnar Loop loop opens toward little finger
• Radial Loop loop opens toward the thumb
• Type Lines pattern area of the loop surrounded
  by two diverging ridges
• Delta the point directly in front of the
  diverging ridgesloops MUST have at least one
  delta
• Core the center of pattern

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Types of Whorl Patterns

• Four types of patterns
• Plain Whorl
• Central Pocket Loop Whorl
• Double Loop Whorl
• Accidental Whorl
• All whorl patterns must have type lines and a
  MINIMUM of two deltas.

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Types of Whorl Patterns

• Plain and Central Pocket Loops
• Plain whorl and central pocket loops have AT
  LEAST one ridge that makes a complete circuit
• Ridge may be a spiral, oval, or any variant of a
  circle

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Types of Whorl Patterns

• Plain Whorl an imaginary line is drawn between
  TWO deltas and the spiral is crossed
• Central Pocket Loop spiral is not crossed when
  imaginary line is drawn

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Types of Whorl Patterns

• Double Loop has two loops in one fingerprint
• Accidental Loop has two or more patterns or is
  not classified into any other category

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Types of Whorl Patterns
Figure 14-6
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Arch Patterns

• Plain arch ridges entering one side of the
  fingerprint and exiting the other side
• Tented arch this pattern rises sharply in the
  center

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Arch Patterns
Figure 14-7
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Classification of Fingerprints

• Original System Henry System
• Developed by Scotland Yard in 1901
• Converted ridge patterns on all 10 fingers into a
  series of letters and numbers arranged into a
  fraction
• Problem could only classify fingerprints up to
  100,000 files
• Evolved into the FBI System of Fingerprint
  Classification

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FBI System

• Primary System of Classification based on the
  Henry System
• All fingerprints in the world can be classified
  into 1,024 groups

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How the FBI System Works

• Fingers are given numbers based on whorl patterns
  being present on each finger
• R. Index R. Ring L. Thumb L.
  Middle L. Little 1
• R. Thumb R. Middle R. Little L.
  Index L. Ring 1
• 16 8 4 2 0 Whorl
  Values
• Zeros are assigned for loops and arches
• Fraction gives individualized result for each
  person

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Problems with FBI System

• 25 of population falls into the 1/1 category
• Only useful when all 10 prints are available
• Cumbersome and Time Consuming to look through
  cards
• Often only one or two prints found at a crime
  scene

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AFIS

• Automated Fingerprint Identification System
• Computer-scans and digitally encodes fingerprints
  based on minutiae of ridge endings and
  bifurications
• List of prints is generated then a fingerprint
  examiner confirms match

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Benefits of AFIS

• Computer can make thousands of accurate
  fingerprint comparisons in a second
• Can filter out imperfections in latent prints
  found at a crime scene
• Suspect lists are generated faster and
  investigators can spend more time focusing on
  suspects

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A Typical AFIS Matching Screen
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Types of Crime Scene Prints

• Three Types
• Visible Prints
• Plastic Prints
• Latent (Invisible) Prints

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Visible Prints

• Can be seen with the naked eye
• Made by fingers touching a surface after ridges
  have been in contact with a colored material such
  as blood, paint, grease, ink, etc.

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Plastic Prints

• Can be seen with the naked eye
• Made by ridge impressions left on a soft material
  such as putty, wax, soap, dust, wet paint
  surfaces, etc.

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Latent Prints

• Cannot be seen with the naked eye
• Made by impressions caused by transfer of body
  perspiration or oils present on finger ridges to
  the surface of an object

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Detection of Prints

• Latent prints must be developed (found) through
  different methods
• The method used is dependent on the surface being
  examined

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Surface Conditions

• Hard, nonabsorbent surfaces (glass, mirrors,
  tile, painted wood) Powders or SuperGlue Fuming
• Absorbent surfaces (paper, cardboard, cloth) One
  or more specific chemicals

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Fingerprint Powders

• Non-absorbent surfaces only
• Applied with a camels hair or fiberglass brush
• Color of powder chosen contrasts with surface
  color
• Powder adheres to oils and perspiration left by
  ridges
• Print can be lifted off the surface and preserved

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Iodine Fuming

• Oldest chemical method for developing latent
  prints
• Iodine is a solid crystal that, when heated, is
  transformed into a gas through sublimation
• Material is placed in a chamber and iodine is
  heated and latent prints are revealed
• Iodine prints are not permanent and must be
  photographed immediately or fixed with starch
  solution, which can last about 1 month

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Ninhydrin

• Chemical used to develop prints on porous
  material by reacting with amino acids in
  perspiration
• Developed prints appear purple-blue in color
• Prints appear within an hour or two and fully
  developed in 24-48 hours
• Commonly used on paper products

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Latent Prints recovered on paper with Ninhydrin
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Physical Developer

• Silver-nitrate based chemical
• Useful for detecting prints that cannot be found
  by other methods or on objects that have been wet
  at one time
• Application of Physical Developer washes away any
  protein that may be present and MUST be used last

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SuperGlue Fuming

• Used on nonporous surfaces such as metal,
  electrical tape, leather, and plastic bags
• Active ingredient cyanoacrylate ester
• Evidence is placed in a fuming chamber and the
  cyanoacrylate is heated and covers the object and
  produces a white latent print

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Flashlight battery exposed to SuperGlue Fuming
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Laser Light

• Perspiration contains a variety of components
  that fluoresce when illuminated by laser light
• Because of the fluorescence, latent prints can be
  seen with the naked eye
• Almost never used anymore with the invention of
  alternate light source latent print examination

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Alternate Light Source

• Works because perspiration fluoresces under
  different wavelengths of light
• Can adjust the wavelength of light to be aimed
  through a fiber optic cable
• More commercially available than laser light
  setups

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Alternative Light Source being used to detect
latent prints
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Preservation of Prints

• Common fingerprint methods do not interfere with
  further DNA analysis
• However, when biological material remains,
  fingerprints should be developed at the crime lab
  instead of at a crime scene

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Preservation of Prints

• After prints have been found, photos must be
  taken
• If object is small enough to be transported
  without destroying the print, it should be
  preserved intact
• Cellophane should cover the print to protect from
  damage

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Preservation of Prints

• Prints on immovable objects should be lifted
• Lifted prints should be preserved on a card that
  provides contrast

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