Download Fingerprint Lesson - Marblehead High School

C6: Fingerprint Analysis
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Forensic Science: Fundamentals & Investigations, Chapter 6
Chapter 6 Fingerprints
By the end of this chapter you will be able to:
 discuss the history of fingerprinting
 describe the characteristics of fingerprints and
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fingerprinting minutiae
explain when and how fingerprints are formed
describe what causes fingerprints to be left on objects
identify the basic types of fingerprints
describe how criminals attempt to alter their fingerprints
All Rights Reserved South-Western / Cengage Learning © 2009
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Forensic Science: Fundamentals & Investigations, Chapter 6
Chapter 6 Fingerprints
By the end of this chapter you will be able to:
 determine the reliability of fingerprints as a means of
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identification
describe the Integrated Automated Fingerprint
Identification System (IAFIS)
explain how fingerprint evidence is collected
describe the latest identification technologies
determine if a fingerprint matches a fingerprint on
record
use the process of lifting a latent print
Forensic Science: Fundamentals & Investigations, Chapter 6
Historical Development
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1.
The oldest known documents showing fingerprints date
from third century B.C. China.
2.
In ancient Babylon (dating back to 1792-1750 B.C.),
fingerprints pressed into clay tablets marked contracts.
3.
The earliest written study (1684) is Dr. Nehemiah’s paper
describing the patterns he saw on human hands under a
microscope, including the presence of ridges.
4.
In 1788, Johann Mayer noted that the arrangement of
skin ridges is never duplicated in two persons. He was
probably the first scientist to recognize this fact.
Forensic Science: Fundamentals & Investigations, Chapter 6
Historical Development
5.
Nine fingerprint patterns were described in
1823 by Jan Evangelist Purkyn.
6.
Sir William Herschel (shown at the right), in
1856, began the collection of fingerprints and
noted they were not altered by age.
7.
Alphonse Bertillon created a way to identify
criminal’s prints that was used in 1883 to
identify a repeat offender.
In 1888, Sir Francis Galton (shown at the
right), and Sir Edmund Richard Henry,
developed the fingerprint classification system
that is still in use in the United States.
8.
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Forensic Science: Fundamentals & Investigations, Chapter 6
Historical Development
9.
In 1891, Iván (Juan) Vucetich improved fingerprint
collection. He began to note measurements on
identification cards, as well as adding all ten fingerprint
impressions. He also invented a better way of collecting
the impressions.
10. Beginning in 1896, Sir Henry (mentioned in the last entry
on the previous slide), with the help of two colleagues,
created a system that divided fingerprints into groups.
Along with notations about individual characteristics, all
ten fingerprints were imprinted on a card (called a ten
card).
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Forensic Science: Fundamentals & Investigations, Chapter 6
Old Method of Identification (pre1990)
Could
take up
to three
months
to find a
match
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Forensic Science: Fundamentals & Investigations, Chapter 6
What was he looking at?
A ten card
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Forensic Science: Fundamentals & Investigations, Chapter 6
IAFIS
Automated fingerprint identification service
links police forces internationally
Results within two hours
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Forensic Science: Fundamentals & Investigations, Chapter 6
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
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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
Forensic Science: Fundamentals & Investigations, Chapter 6
Fingerprints are possible
because:
 Fingers
have unique ridge
patterns
 Fingers produce secretions
 These secretions stick to surfaces
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Forensic Science: Fundamentals & Investigations, Chapter 6
Did You Know?
 Your
fingerprints are hereditary
 They are totally unique
 They will never change
 They form in the dermal papillae
and will always return even after
scarring or burning
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Forensic Science: Fundamentals & Investigations, Chapter 6
Did You Know?
Gloves do not necessarily keep you from
leaving fingerprints
 You can leave prints through surgical
gloves
 They can be turned inside out to produce
a print also
 Leather works this way too
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Forensic Science: Fundamentals & Investigations, Chapter 6
Secretions from fingers
include:
Oils
Salt
Water
Proteins
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Forensic Science: Fundamentals & Investigations, Chapter 6
What Are Fingerprints?
 All fingers, toes, feet, and palms are covered in small
ridges.
 These ridges are arranged in connected units called
dermal, or friction, ridges.
 These ridges help us get or keep our grip on objects.
 Natural secretions plus dirt on these surfaces leave
behind an impression (a print) on those objects with
which we come in contact.
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Forensic Science: Fundamentals & Investigations, Chapter 6
Your skin:
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Forensic Science: Fundamentals & Investigations, Chapter 6
Formation of Fingerprints
 An animal’s external tissue (skin) consists of (a) an
inner dermis and (b) an outer epidermis.
 The creation of fingerprints occurs in a special layer
(the basal layer) in the epidermis where new skin
cells are produced.
 Fingerprints probably begin forming at the start of
the 10th week of pregnancy.
 Because the basal layer grows faster than the
others, it collapses, forming intricate shapes.
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Forensic Science: Fundamentals & Investigations, Chapter 6
Fingerprints are:
 Visible
on surfaces such as a
drinking glass, mirror or other
smooth, reflective surface
Or
 Invisible (called Latent) and have
to be treated to be visible
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Forensic Science: Fundamentals & Investigations, Chapter 6
Fingerprint surfaces
Practically any surface including:
 Wood
 Cardboard
 Objects in water
 Skin (neck, bruises elsewhere)
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Forensic Science: Fundamentals & Investigations, Chapter 6
Fingerprint Patterns
 Eight
basic patterns recognized
by the FBI
 Ten basic details within the
patterns
 At least 12 identical points are
necessary for a match
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Forensic Science: Fundamentals & Investigations, Chapter 6
Characteristics of Fingerprints
 There are 3 general fingerprint distinctions:
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ARCH
WHORL
LOOP
About 5%
of the population
About 30%
About 65%
Forensic Science: Fundamentals & Investigations, Chapter 6
Fingerprints include:
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
Loops
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Whorls
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Arches
Forensic Science: Fundamentals & Investigations, Chapter 6
Characteristics of Fingerprints
 Basic patterns can be further divided:
– Arch patterns can be plain (4%) or tented
(1%).
– Whorl patterns can be central pocket (2%),
double loop (4%), or accidental (0.01%).
 Even twins have unique fingerprints due to
small differences (called minutiae) in the
ridge patterns.
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Forensic Science: Fundamentals & Investigations, Chapter 6
Characteristics of an 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
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Forensic Science: Fundamentals & Investigations, Chapter 6
Tented Arch
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Forensic Science: Fundamentals & Investigations, Chapter 6
Plain Arch
Characteristics of a 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?
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Forensic Science: Fundamentals & Investigations, Chapter 6
Examples of Loop Patterns
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Forensic Science: Fundamentals & Investigations, Chapter 6
Characterics of Whorls
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.
Types
Plain
Central pocket
Double loop
Accidental
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Forensic Science: Fundamentals & Investigations, Chapter 6
Examples of Whorl Patterns
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Forensic Science: Fundamentals & Investigations, Chapter 6
Notice the scar
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Forensic Science: Fundamentals & Investigations, Chapter 6
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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Forensic Science: Fundamentals & Investigations, Chapter 6
Ridge patterns
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Forensic Science: Fundamentals & Investigations, Chapter 6
Ridge Patterns
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Forensic Science: Fundamentals & Investigations, Chapter 6
Comparison of Fingerprints
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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Forensic Science: Fundamentals & Investigations, Chapter 6
Types of Fingerprints
There are 3 types of prints that
investigators look for at crime scenes:
1. Patent fingerprints are visible prints transferred
onto smooth surfaces by blood or other liquids.
2. Plastic fingerprints are indentations left in soft
materials such as clay or wax.
3. Latent fingerprints are not visible but made so
by dusting with powders or the use of chemicals.
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Forensic Science: Fundamentals & Investigations, Chapter 6
Latent Fingerprints
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Can be treated with various powders to
help see the ridge patterns better.
These powders include:
manganese dioxide
graphite
a trace of metals in them (like aluminum).
Forensic Science: Fundamentals & Investigations, Chapter 6
Powders
Gray for dark objects
 Black for light colored objects
 Chalk dust can be used if viewed on a
dark background
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Prints can be ‘lifted’ off a surface
using adhesive tape
Forensic Science: Fundamentals & Investigations, Chapter 6
Latent prints can be
visualized using
‘Superglue’ in a sealed chamber
 Using iodine vapor in a sealed
chamber
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Forensic Science: Fundamentals & Investigations, Chapter 6
Fingerprint Forensic FAQs
 How are latent fingerprints collected?
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Forensic Science: Fundamentals & Investigations, Chapter 6
Developing Latent Fingerprints
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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Forensic Science: Fundamentals & Investigations, Chapter 6
Developing Latent Prints, cont’d
Ninhydrin—reacts with amino acids to produce a purple color.
Silver nitrate—reacts with chloride to form silver chloride, a material
that turns gray when exposed to light.
Cyanoacrylate—“superglue” 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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Forensic Science: Fundamentals & Investigations, Chapter 6
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 up to 2 hours for the prints in its Master File.
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Forensic Science: Fundamentals & Investigations, Chapter 6
A famous set of prints
John
Dillinger
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Forensic Science: Fundamentals & Investigations, Chapter 6
Other Prints: Ear Print
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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Forensic Science: Fundamentals & Investigations, Chapter 6
The Future of Fingerprinting
 New scanning technologies and digitally
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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Forensic Science: Fundamentals & Investigations, Chapter 6
. . . . . . . . . . . . . . . . . Summary
 Fingerprints have long been used for identification, and in
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the mid-1800s were recognized as unique to each person.
Three main groups include arches, whorls, and loops.
Basic analysis includes looking for cores, deltas, and
making a ridge count.
Investigators search for patent, plastic, and latent prints.
Dusting with powders or using special chemicals can make
latent fingerprints visible.
New developments may eliminate errors by analysts.
Forensic Science: Fundamentals & Investigations, Chapter 6