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Chapter 4: Fingerprints

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Why fingerprints are individual evidence. ... Carboxylic acid and amine groups. Chapter 4. Ninhydrin Reaction. Chapter 4. Silver Nitrate Reaction ... – PowerPoint PPT presentation

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Title: Chapter 4: Fingerprints


1
Chapter 4 Fingerprints
Fingerprints cannot lie, but liars can make
fingerprints. Unknown
2
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.

3
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.

4
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

5
Fundamental Principlesof Fingerprints
  • Individual characteristic
  • Unchanged during an individuals lifetime.
  • General characteristic ridge patterns for
    systematic classification

6
Why do we have fingerprints?
  • Provides better grip
  • Makes perspiration easier on a hairless surface
  • Improves sense of touch
  • ?????

7
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)

8
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
9
Whorl
  • Whorls have at least two deltas and a core.
  • Four Groups
  • Plain
  • Central Pocket
  • Double Loop
  • Accidental

Plain Whorl
10
Whorl
  • Central Pocket

11
Whorl
  • Double loop

12
Whorl
  • Accidental

13
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

14
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

15
Primary Classification
The HenryFBI Classification Based on WHORLS Each
finger is given a point value
right
left
16
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
17
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

18
Ridge Characteristics
  • Minutiaecharacteristics of ridge patterns
  • Ridge ending
  • Short ridge
  • Dot or fragment
  • Bifurcation
  • Double bifurcation
  • Trifurcation
  • Bridge
  • Island
  • Enclosure
  • Spur

19
Comparison
  • Can you identify the points?

20
Fingerprint Minutiae
21
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

22
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.

23
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.

24
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.

25
Iodine Fingerprint
26
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.

27
Ninhydrin Fingerprint
28
What are amino acids?
Carboxylic acid and amine groups
29
Ninhydrin Reaction
30
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

31
Cyanoacrylate Fingerprints
32
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.

33
Other Prints
  • Palmfriction ridges can be identified and
    may be used against suspects.

34
Other Prints
  • Footprints are taken at birth as a means of
    identification of infants.

35
Other Prints
  • Lipsdisplay several common patterns
  • Short vertical lines
  • Short horizontal lines
  • Crosshatching
  • Branching grooves

36
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.

37
Other Prints
  • The blood vessel patterns in the eye may be
    unique to individuals. They are used today for
    various security purposes.

38
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

39
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.

40
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
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