Transcript Fingerprints

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 (IFAIS)
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.
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Historical Development
5.
Nine fingerprint patterns were described in
1823 by Jan Evangelist Purkyn.
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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
criminals that was used in 1883 to identify a
repeat offender.
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8.
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In 1902, he was credited with solving the first murder using fingerprints.
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.
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
based on whether they had an arch, loop, or whorl
pattern. Along with notations about individual
characteristics, all ten fingerprints were imprinted on a
card (called a ten card).
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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.
 Natural secretions from the sweat glad in the friction ridge of the
skin are a combination of mainly water, oils, and salts.
 Dirt from everyday activities also mixes into the secretions.
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 Anytime you touch something you leave behind traces of these
substances in the unique pattern of your dermal ridges.
Sweat Pore
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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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Formation of Fingerprints
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Patterns are probably formed the during the 10th week of
pregnancy along with prints of the palms of the hands, soles
of the feet, and lip prints.
The creations of fingerprints happens in the basal layer, a
specialized area within the epidermis where new skin cells
are produced.
In a fetus, this layer grows faster than the epidermis
(outside) and dermis (inside) thus the layer collapses and
folds in different directions creating intricate shapes between
the other layers of skin.
The pattern cannot be altered or destroyed permanently by
skin injuries because the outer layer protects it.
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%
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Loop
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Whorl
Arch
Characteristics of Fingerprints
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Named for their general visual appearance and patterns.
Called loops, whorls, and arches.
Arches(5% of the population has this type):
– have ridges that enter from one side of the fingerprint and
leave from the other side with a rise in the center.
Whorls (30% of the population has this type):
– Look like a bull’s-eye with two deltas (triangles).
Loops (65 % of the population has this type):
– Enter from either the right or the left and exit from the
same side they enter.
Characteristics of Fingerprints
 Basic patterns can be further divided:
– Arch patterns can be plain (4%) or tented
(1%).
– Whorl patterns can be a plain whorl (24%) a
central pocket loop whorl (2%), double loop
whorl (4%), or accidental (0.01%).
 Even twins have unique fingerprints due to
small differences (called minutiae) in the
ridge patterns.
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CHARACTERISTICS OF FINGERPRINTS
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Forensic Science: Fundamentals & Investigations, Chapter 6
Whorls
 Basic patterns can be further divided:
– Whorl patterns can be a plain whorl (24%) a central
pocket loop whorl (2%), double loop whorl (4%), or
accidental (0.01%).
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Whorls (cont.)
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The plain whorl has one or more ridges that make a
complete spiral. There are two deltas, and if a line is drawn
between them, at least one ridge in the inner pattern is
touched or cut by the line.
The central pocket loop whorl has one or more ridges that
make a complete circle. There are two deltas, and if a line is
drawn between them, no ridges in the inner pattern are
touched or cut by the line.
The double loop whorl has two separate loop formations and
two deltas.
The accidental whorl has two or more deltas and is a
combination of two of the other patterns (but not a plain
arch).
Arches
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Arches can be further divided:
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Plain arches (4%) and tented arches (1%).
The plain arch shows ridges entering one side,
rising in the center, and flowing out the other side
without making an angle.
The plain arch has no characteristics of the loop
pattern.
The tented arch does form an angle, or it may
possess some characteristic of the loop pattern,
such as a delta.
CHARACTERISTICS OF FINGERPRINTS
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Arches (cont.)
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CHARACTERISTICS OF
FINGERPRINTS
Forensic examiners look for
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Core (the center of a whorl or
loop)
●Deltas (triangular regions near a
loop)
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Ridge count
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Counting from the core to the edge
of the delta
●Distinguishes one fingerprint from
another
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To take a ridge count, an
imaginary line is drawn from the
center of the core to the edge of
the delta.
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EXAMPLE OF A TEN CARD
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Characteristics of Fingerprints
(cont.)
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Every individual, including identical twins,
has a unique fingerprint resulting from unique
ridge patterns called minutiae.
There are about 150 individual ridge
characteristics on the average full fingerprint.
To match fingerprints, a minimum number of
points of comparison are needed. (12-18
points needed)
Forensic Science: Fundamentals & Investigations, Chapter 6
Pictures of minutiae
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See page 139 for
more examples of
minutiae patterns
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Types of Fingerprints
There are 3 types of prints that
investigators look for at crime scenes:
1. Patent fingerprints are visible prints transferred
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onto smooth surfaces by blood or other liquids.
2. Plastic fingerprints are indentations left in soft
materials such as clay, putty, or wax.
3. Latent fingerprints, or hidden prints, are caused
by the transfer of oils and other body secretions
onto a surface. They can be made visible by
dusting with powders or the use of chemicals.
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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Fingerprint Forensic FAQs
 How are latent fingerprints collected?
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How Are Fingerprints Analyzed?
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By 1987, the FBI had 23 million criminal fingerprint cards
on file. Finding a match sometimes took up to 3 months.
In 1999, with cooperation of the national law enforcement
community, the FBI developed the Integrated Automated
Fingerprint Identification System (AFIS). Linked with
authorities globally it became IAFIS.
IAFIS provides digital, automated fingerprint searches,
latent searches, and electronic exchange of fingerprints
and test results.
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
THE FUTURE OF FINGERPRINTING
New scanning technologies
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Yield detail in minute patterns
●Reduce analytical mistakes
●Analyze trace elements of objects on the skin
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To help with identification, other physical features
such as eyes and facial patterns are also being
studied.
Retina
●Face
●Veins in your palm
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. . . . . . . . . . . . . . . . . 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