Chapter 4: Fingerprints

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Chapter 4 Fingerprints
Fingerprints cannot lie, but liars can make
fingerprints. Unknown
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Fingerprints
Students will learn

• Why fingerprints are individual evidence.
• Why there may be no fingerprint evidence at a
  crime scene.
• How computers have made personal identification
  easier.

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Students will be able to
Fingerprints

• Define the three basic properties that allow
  individual identification by fingerprints.
• Obtain an inked, readable fingerprint for each
  finger.
• Recognize the general ridge patterns (loops,
  whorls, and arches)
• Identify friction ridge characteristics and
  compare two fingerprints with at least ten points
  of identification.
• Explain the differences among latent, plastic,
  and visible fingerprints.
• Develop latent prints (make them visible) using
  physical and chemical methods.

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Fingerprints

• Recording and Classifying Prints
• rolling inked prints
• primary identification number
• Lifting Latent Prints
• Black, white, magnetic, and fluorescent powder
• Chemicalsninhydrin, iodine, silver nitrate,
  cyanoacrylate
• Other Types of Prints
• Palm, lip, teeth, eye, ear, voice, shoe and
  footprints

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Fundamental Principlesof Fingerprints

• Individual characteristic
• Unchanged during an individuals lifetime.
• General characteristic ridge patterns for
  systematic classification

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Why do we have fingerprints?

• Provides better grip
• Makes perspiration easier on a hairless surface
• Improves sense of touch
• ?????

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Classification of Fingerprints

• Three basic patterns
• Loop
• 65
• Whorls
• 10-20
• Arches
• 5
• Racial variations (African (more arches),
  European (more loops), Asians/Orientals (more
  whorls)

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Loop

• A loop must have one or more ridges entering and
  exiting from the same side. Loops must have one
  delta.
• Types
• Radialopens toward the thumb
• Ulnaropens toward the pinky (little finger)
• Which type of loop is this, if it is on the right
  hand? Left hand?

Delta
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Whorl

• Whorls have at least two deltas and a core.
• Four Groups
• Plain
• Central Pocket
• Double Loop
• Accidental

Plain Whorl
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Whorl

• Central Pocket

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Whorl

• Double loop

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Whorl

• Accidental

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Arch

• Friction ridges that enter on one side of the
  finger and cross to the other side while rising
  upward in the middle.
• They do NOT have type lines, deltas, or cores.
• Types
• Plain
• Tented

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Henry-FBI Classification

• Developed by Edward Henry
• Allowed all sets of ten fingerprints in the world
  to be divided into 1024 groups
• Secondary and more complex classifications were
  created to allow for more groups

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Primary Classification
The HenryFBI Classification Based on WHORLS Each
finger is given a point value
right
left
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Primary Classification

• Assign the number of points for each finger
  that has a whorl and substitute into the equation

right right left left
left index ring thumb
middle little 1

right right right left
left thumb middle little
index ring 1
That number is your primary classification number
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Individualization

• Henry-FBI Classification
• Narrows into a group
• Ridge Classification
• Uses minutiae to individualize fingerprints
• In U.S. there are no legal requirements for of
  points
• Criminal courts accept 8 to 12 points
• 150-200 minutiae in a good rolled print

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Ridge Characteristics

• Minutiaecharacteristics of ridge patterns

• Ridge ending
• Short ridge
• Dot or fragment
• Bifurcation
• Double bifurcation
• Trifurcation
• Bridge
• Island
• Enclosure
• Spur

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Comparison

• Can you identify the points?

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Fingerprint Minutiae
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DactyloscopyThe study of fingerprints

• Historically
• William Herschelrequired Indians to put their
  fingerprints on contracts, and also as a means of
  identifying prisoners
• Henry Fauldsclaimed that fingerprints did not
  change over time and that they could be
  classified for identification
• Alphonse Bertillonproposed body measurements as
  a means of identification termed anthropometry
• Francis Galtondeveloped a primary classification
  scheme based on loops, arches and whorls.
• Edward Richard Henryin collaboration with Galton
  instituted a numerical classification system
• Juan Vucetichdeveloped a fingerprint
  classification based on Galtons that is used in
  Spanish-speaking countries

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Latent Prints

• Latent fingerprints
• Hidden
• Natural secretions of human skin
• Require development for them to become visible
• Most secretions come from three glands
• Eccrinelargely water with both inorganic
  (ammonia, chlorides, metal ions, phosphates) and
  organic compounds (amino acids, lactic acids,
  urea, sugars). Most important for fingerprints.
• Apocrinesecrete pheromones and other organic
  materials.
• Sebaceoussecrete fatty or greasy substances.

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Developing Latent Prints

• Requires substances that interact with secretions
  
• Attempt more than one technique, done in a
  particular order so as not to destroy the print
• 5 Types of Chemical Development Methods
• Powdersadhere to both water and fatty deposits.
  Choose a color to contrast the background.
• Iodinefumes react with oils and fats to produce
  a temporary yellow brown reaction.

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Developing Latent Prints

• Ninhydrinreacts with amino acids to produce a
  purple color.
• Silver nitratereacts with chloride to form
  silver chloride, a material which turns gray when
  exposed to light.
• Cyanoacrylatesuper glue fumes react with water
  and other fingerprint constituents to form a
  hard, whitish deposit.
• In modern labs and criminal investigations,
  lasers and alternative light sources are used to
  view latent fingerprints. These were first used
  by the FBI in 1978. Since lasers can damage the
  retina of the eye, special precautions must be
  taken.

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Iodine Fingerprint
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Iodine Reaction

• Occurs as an addition reaction involving the CC
  bonds in fats
• Iodine (I2) comes in breaks the CC bond and one
  iodine attaches to each C.

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Ninhydrin Fingerprint
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What are amino acids?
Carboxylic acid and amine groups
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Ninhydrin Reaction
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Silver Nitrate Reaction

• AgNO3 reacts with Chlorides (from salt in sweat)
  to form the solid AgCl
• Ag Cl- ? AgCl
• Silver chloride (AgCl) is a white solid that
  turns brown when exposed to the sun or other UV
  light source

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Cyanoacrylate Fingerprints
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Other Prints

• Earsshape, length and width
• Voiceelectronic pulses measured on a
  spectrograph
• Footsize of foot and toes friction ridges on
  the foot
• Shoescan be compared and identified by type of
  shoe, brand, size, year of purchase, and wear
  pattern.

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Other Prints

• Palmfriction ridges can be identified and
  may be used against suspects.

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Other Prints

• Footprints are taken at birth as a means of
  identification of infants.

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Other Prints

• Lipsdisplay several common patterns
• Short vertical lines
• Short horizontal lines
• Crosshatching
• Branching grooves

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Other Prints

• Teethbite marks are unique and can be used to
  identify suspects. These imprints were placed in
  gum and could be matched to crime scene evidence.

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Other Prints

• The blood vessel patterns in the eye may be
  unique to individuals. They are used today for
  various security purposes.

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AFIS

• The Automated Fingerprint Identification System
• Began in the early 1970s to
• Search large files for a set of prints taken from
  an individual
• Compare a single print, usually a latent print
  developed from a crime scene
• By the 1990s most large jurisdictions had their
  own system in place. The problem - a persons
  fingerprints may be in one AFIS but not in others
• IAFISthe FBIs Integrated Automated Fingerprint
  Identification system which is a national
  database of all 10-print cards from all over the
  country

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Biometrics

• Use of some type of body metrics for the purpose
  of identification. (The Bertillon system may
  actually have been the first biometry system.)
• Used today in conjunction with AFIS
• Examples include retinal or iris patterns, voice
  recognition, hand geometry
• Other functions for biometricscan be used to
  control entry or access to computers or other
  structures can identify a person for security
  purposes can help prevent identity theft or
  control social services fraud.

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More about Prints

• For additional information about prints and
  crime, check out Court TVs Crime Library
• www.crimelibrary.com/criminal_mind/forensics/finge
  rprints/1.html