Chapter 4 - Fingerprints

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Chapter 4 - Fingerprints
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What is a fingerprint?

• An imprint made by ridge patterns on the tip of a
  finger.
• Also used to describe the characteristic pattern
  of DNA fragments.

Why are fingerprints useful?

• Properties that make a fingerprint useful for ID
• Its unique characteristic ridges which make them
  individual evidence.
• Its consistency over a persons lifetime. It
  remains unchanged during an individuals
  lifetime.
• The systematic classification is used for
  fingertips based on their general characteristic
  ridge patterns.

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DactyloscopyThe Study of Fingerprints

• History from 1850 to 1900
• William Herschelrequired Indians to put their
  fingerprints on contracts, and used fingerprints
  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 system based on Galtons that is
  used in Spanish-speaking countries

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Collection and Classification of Prints

• Recording and classifying prints
• Rolling inked prints
• 3 Basic patterns - Loops, whorls, arches
• Ridge characteristics Minutiae (very small)
• Primary identification number

Lifting prints Black, white, and fluorescent
powder Chemicalsninhydrin, iodine, silver
nitrate, cyanoacrylate Other types of
prints Palm, lip, teeth, eye, ear, voice,
shoeprints, and footprints
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Ridge Characteristics

• Minutiaecharacteristics of ridge patterns

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Fingerprint Minutiae
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LOOP
Basic Fingerprint Patterns
WHORL
ARCH
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Arch

• An arch has 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.
• Least common type (5) and more likely found in
  people of African ancestry.
• Types
• Plain gradual bump
• Tented much higher, pinched arch

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Loop

• A loop must have one or more ridges entering from
  one side, curving around and exiting from the
  same side. Loops must have one delta.
• Most common type (65) and more common in people
  of European background. Also, forefingers have
  most of the radial loops.
• 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?

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Whorl

• A plain or central pocket whorl has at least one
  ridge that makes a complete circuit. A double
  loop is made of two loops. An accidental is a
  pattern not covered by other categories. Whorls
  have at least two deltas and a core.
• Found in 30 of population. People of Asian
  ancestry are more likely to have whorls.
• Types
• Plain
• Central pocket
• Double loop
• Accidental

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Four Types of Whorls

• Whorl line drawn
• from delta to delta intersect circle.

• Central Pocket line drawn from delta to delta do
  not intersect circle.

• Accidental prints too irregular to fall into any
  group.

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Primary Classification
The Henry-FBI Classification System Each finger
is given a point value.
Fingerprints are given as a fraction. Identify
which fingers have whorls each whorl has a
number based on which finger it is on. Loops
and arches are a 0.
Right Right Left Left Left
index ring thumb middle little 16 8 4
2 1 1 Right Right
Right Left Left thumb middle little index ring
16 8 4 2
1 1 Example Whorl on your
left thumb and right middle finger. 0
0 4 0 0 1
5 5 is your primary 0 8
0 0 0 1
9 9 classification
right
left
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Comparison

• There are no legal requirements in the United
  States on the number of points required for a
  match. Generally, criminal courts will accept 8
  to 12 points of similarity.

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Plastic Prints

• Indented of molded prints
• Made by pressing a finger against a plastic like
  material to form a negative impression of a
  fingerprint.
• Examples putty, soap, candle wax, gum, stamps,
  or candy bar.

Visible Prints
Left by a finger that has touched colored
material such as blood, paint, ink, grease,
chalk, mud or sometimes even dust.
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Latent Prints

• Latent fingerprints are those that are not
  visible (essentially invisible) to the naked eye.
  They are impressions caused by the transfer of
  oils present on the finger to the surface of an
  object. These prints consist of the natural
  secretions (body oils and perspirations) of human
  skin and require development by chemical or
  physical means for them to become visible.
• Most secretions come from three glands
• Eccrinesecretes largely water, with both
  inorganic (ammonia, chlorides, metal ions,
  phosphates) and organic (amino acids, lactic
  acids, urea, sugars) compounds. Most important
  for fingerprints.
• Apocrinesecretes pheromones and other organic
  materials.
• Sebaceoussecretes fatty or greasy substances.

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Developing Latent Prints

• Developing a print requires substances that
  interact with secretions, causing the print to
  stand out against its background. It may be
  necessary to attempt more than one technique,
  done in a particular order so as not to destroy
  the print.

• Powders (dusting) -- adhere to both water and
  fatty deposits. Choose a color
• to contrast with the background. Best on hard,
  nonabsorbent surfaces. Develop print by lifting
  with clear sticky tape.
• Iodine (chemical) fumes react with oils and
  fats to produce a
• temporary (short lasting) yellow-brown colored
  print. Works best on
• porous paper.
• Ninhydrin reacts with amino acids to produce an
  orange to purple color. Best with paper, tissue,
  clothing and other porous surfaces.
• Silver nitrate UV Light reacts with chloride
  in salt to form silver chloride, a material
  that turns into silver oxide (gray) when exposed
  to light. Porous surfaces like paper and drywall.
• Cyanoacrylatesuperglue fumes react with water
  and other fingerprint constituents to form a
  hard, whitish deposit that can be treated with
  powders or fluorescent dyes to make a shaper
  contrast for photos or lifting.
• 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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Other Types of Prints

• Palmfriction ridges can be identified and may be
  used against suspects
• Lipsseveral common patterns not individual.
• Voiceelectronic pulses measured on a
  spectrograph
• Footare taken at birth as a means of
  identification of infants.
• Size of foot and toes not individual.
• Friction ridges on the foot and toes
  individual
• Shoescan be compared and identified by type of
  shoe, brand, size, year of purchase, and wear
  pattern

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Other Prints, continued
Earprint catches murderer

• A man has been convicted of suffocating an eldery
  woman on the basis of earprint evidence. The
  assailant was caught after police matched the
  imprint of his ear on the victims window. Police
  believe that the thief put his ear to the window
  to listen for signs of anyone home.

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.
Eyeprint - 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 Systema
  computer system for storing and retrieving
  fingerprints
• Established in the 1970s, AFIS enables law
  enforcement officials 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 database 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 biometrics can 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.