Transcript chapter04

Fingerprints
Fingerprints
Fingerprints
Objectives
You will understand:
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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Fingerprints
Fingerprints
Objectives, continued
You will be able to:
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
Fingerprints
Dactyloscopy
The Study of Fingerprints
History from 1850 to 1900
William Herschel—required Indians to put their fingerprints on contracts, and
used fingerprints as a means of identifying prisoners
Henry Faulds—claimed that fingerprints did not change over time and that they
could be classified for identification
Alphonse Bertillon—proposed body measurements as a means of
identification; termed anthropometry
Francis Galton—developed a primary classification scheme based on loops,
arches, and whorls
Edward Richard Henry—in collaboration with Galton, instituted a numerical
classification system
Juan Vucetich—developed a fingerprint classification system based on
Galton’s that is used in Spanish-speaking countries
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Fingerprints
Fingerprints
Recording and classifying prints
Rolling inked prints
Loops, whorls, arches, ridge characteristics
Primary identification number
Lifting prints
Black, white, and fluorescent powder
Chemicals—ninhydrin, iodine, silver nitrate, cyanoacrylate
Other types of prints
Palm, lip, teeth, eye, ear, voice, shoeprints, and footprints
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Fingerprints
Fingerprints
Fundamental Principles of Fingerprints
1. A fingerprint is an individual
characteristic.
2. A fingerprint remains unchanged
during an individual’s lifetime.
3. Fingerprints have general
characteristic ridge patterns that
permit them to be systematically
classified.
•Fingerprints are a reproduction of friction
skin ridges found on the palm side of the
fingers and thumbs.
•No two fingers have yet been found to
possess identical ridge characteristics.
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Fingerprints
Boundary between
epidermis and dermis is
the dermal papillae,
which determines the
form and pattern of the
ridges on the surface of
the skin. Once this
develops in the human
fetus, the ridge patterns
remain unchanged
throughout life except
to enlarge during
growth.
Cross Section of
Human Skin
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Fingerprints
Characteristics of Fingerprints
 Forensic examiners look for the presence of a core (the center
of a whorl or loop) and deltas (triangular regions near a loop).
 A ridge count is another characteristic that distinguishes one
fingerprint from another. The count is made from the center of
the core to the edge of the delta.
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Fingerprints
Fingerprints
Ridge Characteristics
Minutiae—characteristics of ridge patterns
Ridge ending
Island or
short ridge
Bridge
Eye or enclosure
Delta
Bifurcation or fork
Dot
Spur
Double bifurcation
Trifurcation
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The individuality of a fingerprint is determined not by
its general shape or pattern, but by a careful study of
its ridge characteristics. Prints deposited in this
manner are invisible to the eye and are commonly
referred to as latent or invisible fingerprints.
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Fingerprints
Fingerprint Minutiae
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Fingerprints
Fingerprint Forensic FAQs
 Can fingerprints be erased?
No, if, for example, they are removed with chemicals,
they will grow back.
 Is fingerprint identification reliable?
Yes, but analysts can make mistakes.
 Is fingerprint matching carried out by computers in a
matter of seconds?
No, but the FBI’s Integrated Automated Fingerprint
Identification System (IAFIS or AFIS) can provide a
match in 2 hours for the prints in its Master File.
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Fingerprints
LOOP
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WHORL
ARCH
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Fingerprints
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.
Types
Plain
Tented
About 5% of the
population have arches.
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Fingerprints
Loop
A loop must have one or more ridges
entering and exiting from the same
side. Loops must have one delta.
Types
Radial—opens toward the thumb
Ulnar—opens toward the “pinky”
(little finger)
Which type of loop is this, if it is on
the right hand? Left hand?
60-65% of the population
have loops.
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Fingerprints
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.
30-35% of the population
have whorls.
Types
Plain
Central pocket
Double loop
Accidental
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Fingerprints
Fingerprints
Primary Classification
The Henry-FBI Classification System
Each finger is given a point value.
right
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The primary classification
is the first step in
classifying fingerprints
under the FBI system. The
presence or absence of the
whorl pattern is the basis
for determination of the
primary classification.
Fingerprints
Fingerprints
Primary Classification, continued
Assign the number of points for each finger that has a whorl and
substitute into the equation:
right
index
right
ring
left
thumb
left
middle
left
little
+1
=
right
thumb
right
middle
right
little
left
index
left
ring
+1
That number is your primary classification number.
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Fingerprints
AFIS
The Automated Fingerprint Identification System—a 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 person’s fingerprints may be in one AFIS database but not
in others.
IAFIS—the FBI’s Integrated Automated Fingerprint Identification System,
which is a national database of all 10-print cards from all over the
country
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Fingerprints
Automated Fingerprint Identification Systems
 AFIS
 Can be operated by cities,
counties, other local
government
 Often cannot be linked with
state’s AFIS system because
of differences in software
configurations
 IAFIS
 Integrated AFIS
 Largest AFIS in USA
 Links state AFIS computers
with the FBI database
 Contains nearly 50 million
fingerprint records
The database converts the image of a
fingerprint into digital minutiae that
contain data showing ridges at their
points of termination (ridge endings)
and their branching into two ridges
(bifurcations).
Livescan is an inkless device that
captures digital images of fingerprints
and palm prints and electronically
transmits them to an AFIS.
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Fingerprints
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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Fingerprints
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Matching Minutiae
(must show 8-10)
1.
2.
3.
.
.
.
14.
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Fingerprints
Visible and Plastic Prints
 Visible prints (or patent prints) are made when fingers touch
a surface after the ridges have been in contact with a colored
material such as blood, paint, grease, or ink.
 Plastic prints are ridge impressions left on a soft material,
such as putty, wax, soap, or dust.
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Fingerprints
Latent Prints
Latent fingerprints are those that are not visible to the naked eye.
These prints consist of the natural secretions of human skin and
require development for them to become visible.
Most secretions come from three glands:
Eccrine—secretes largely water, with both inorganic (ammonia,
chlorides, metal ions, phosphates) and organic (amino acids, lactic acids,
urea, sugars) compounds. Most important for fingerprints.
Apocrine—secretes pheromones and other organic materials.
Sebaceous—secretes fatty or greasy substances.
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Fingerprints
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—adhere to both water and fatty deposits. Choose a color
to contrast with the background.
Iodine—fumes react with oils and fats to produce a
temporary yellow-brown color.
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Fingerprints
Developing Latent Prints

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Developing a print requires substances that interact
with secretions that cause 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.
1. Powders—adhere to both water and fatty
deposits. Choose a color to contrast the
background. Best used on nonporous surfaces.
§ Gray for mirrors and dark surfaces, Black for light-colored
surfaces
§ Magnetic powder good for rough surfaces
§ Fluorescent powders are used with UV light so surface
color is obscured
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Iodine Fingerprint
2. Iodine—fumes react with oils and fats to produce a
temporary yellow brown reaction.
§
Prints fade, so they must be photographed or “fixed”
Note the brownish color.
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Ninhydrin Fingerprint
3. Ninhydrin—reacts with amino acids to produce a purple
or pink color.
Preferred method of chemical development on porous surfaces
like paper
Note the pink color.
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Fingerprints
Fingerprints
Developing Latent Prints
4. Silver nitrate—reacts with chloride to form silver
chloride, a material which turns gray when exposed to
light.
Useful on porous surfaces that may have been wet at one time
5. Cyanoacrylate—“super glue” fumes react with water
and other fingerprint constituents to form a hard, whitish
deposit.
§
Used on nonporous surfaces such as metals, electrical tape,
leather, plastic bags.
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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Fingerprints
Cyanoacrylate Fingerprints
Note the white color.
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Fingerprints
Fingerprint Forensic FAQs
 How are latent fingerprints collected?
 One way is to use a chemical.
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Fingerprints
Key Points - Latent Prints
Hard and nonabsorbent surfaces are usually
developed by application of a powder
Porous surfaces (papers, cardboard) generally require
treatment with a chemical
• Iodine fuming, ninhydrin, silver nitrate
Super Glue fuming develops prints on nonporous
surfaces
Chemically induced fluorescence, visible when
exposed to laser or ALS (alternate light source)
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Fingerprints
Fingerprints
The Future of
New scanning technologies and digitally
Fingerprinting
identifying
patterns may eliminate analytical
mistakes.
Trace elements of objects that have been
touched are being studied to help with the
identification of individuals.
To help with identification, other physical
features such as eyes and facial patterns are
also being studied.
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Fingerprints
What is the
pattern of
Mayfield’s print
and that of the
prime suspect?
How are they
similar? How are
they different?
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Fingerprints
Other Prints
Lips—several common patterns
Voice—electronic pulses measured on a spectrograph
Foot—size of foot and toes; friction ridges on the foot
Shoes—can be compared and identified by type of shoe,
brand, size, year of purchase, and wear pattern
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Fingerprints
Fingerprints
Other Prints, continued
Palm—friction ridges can be
identified and may be used
against suspects
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Fingerprints
Fingerprints
Other Prints, continued
Footprints are taken at birth
as a means of identification of
infants.
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Fingerprints
Fingerprints
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 inprint
of his ear on the victim’s window.
Police believe that the thief put his ear
to the window to listen for signs of
anyone home.
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Fingerprints
Fingerprints
Other Prints, continued
Teeth—bite 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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Fingerprints
Other Prints, continued
The blood vessel patterns in
the eye may be unique to
individuals. They are used
today for various security
purposes.
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Other Prints Fingerprints
Fingerprints
Lips—display several
common patterns




Short vertical lines
Short horizontal lines
Crosshatching
Branching grooves
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Kendall/Hunt
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Publishing Company
Fingerprints
Fingerprints
What does one do with the developed print ?
Photograph the print with
a close-up lens
Cover print with
cellophane tape, preserve
entire object containing
print
“Lift” print off larger
objects with clear tape,
mount on backing card
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Kendall/Hunt
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Publishing Company
Fingerprints
Fingerprints
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.
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Fingerprints
More about Prints
For additional information about prints and crime, check out
truTV’s Crime Library:
www.crimelibrary.com/criminal_mind/forensics/fingerprints/1.html
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