Transcript Fingerprints ppt

Chapter 6 Fingerprints
By the end of this chapter you will be able to:
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Discuss the history of fingerprinting
Describe the characteristics of fingerprints and
fingerprinting minutiae
Explain when and how fingerprints form
Describe how fingerprints can 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 © 2012, 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:
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Determine the reliability of fingerprints as a
means of 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.
3rd century B.C. in China—oldest known
documents
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Ancient Babylon (1792-1750 B.C.)—fingerprints
pressed into clay tablets marked contracts
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1684—Dr. Nehemiah’s paper describes the patterns
on human hands, including the presence of ridges
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1788—Johann Mayer noted that the arrangement of
skin ridges is never duplicated in two persons
Forensic Science: Fundamentals & Investigations, Chapter 6
Historical Development
5. 1823—Jan Evangelist Purkyn describes nine
fingerprint patterns
6. 1856—Sir William Herschel (right) began the
collection of fingerprints and noted they were
not altered by age
7. 1883—Alphonse Bertillon created a way to
identify criminals that were repeat offenders
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Historical Development
8. 1888—Sir Francis Galton (r) and Sir Edmund
Richard Henry developed the fingerprint
classification system still used in the US
9. 1891—Iván (Juan) Vucetich collected all ten
fingerprint impressions and noted measurements
10. 1896—Sir Henry, with two colleagues, created a
system that divided fingerprints into groups. All ten
fingerprints are imprinted on a card (called a ten
card) along with other notations
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Forensic Science: Fundamentals & Investigations, Chapter 6
Example of a Ten Card
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Forensic Science: Fundamentals & Investigations, Chapter 6
What Are Fingerprints?
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All fingers, toes, feet, and palms are covered
in small ridges
Ridges help us grip objects
Ridges are arranged in connected units called
dermal, or friction, ridges
Fingers accumulate natural secretions and dirt
Fingers leave create prints on objects we
touch
Forensic Science: Fundamentals & Investigations, Chapter 6
Structure of Skin
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Forensic Science: Fundamentals & Investigations, Chapter 6
Formation of Fingerprints
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Skin consists of:
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Inner layer—dermis
Outer layer—epidermis
Dermal Papillae - Basal layer in between
Basal layer grows faster than the layers above and
below it
Basal layer collapses and folds to form intricate
shapes
Fingerprints begin forming near the 10th week of
pregnancy
Forensic Science: Fundamentals & Investigations, Chapter 6
Characteristics of Fingerprints
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There are 3 general fingerprint distinctions:
ARCH
WHORL
LOOP
About 5%
About 30%
About 65%
of the population
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Forensic Science: Fundamentals & Investigations, Chapter 6
Characteristics of Fingerprints
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Forensic examiners look for
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Ridge count
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Core
(the center of a whorl or loop)
Deltas
(triangular regions near a loop)
Counting from the core to the
edge of the delta
Distinguishes one fingerprint
from another
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Forensic Science: Fundamentals & Investigations, Chapter 6
Loops
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A loop must have one or more ridges
entering from one side of the print,
recurving, and exiting from the same
side.
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If the loop opens toward the little finger, it
is called an ulnar loop.
If the loop opens toward the thumb, it is
called a radial loop.
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Forensic Science: Fundamentals & Investigations, Chapter 6
Characteristics of Fingerprints
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Forensic Science: Fundamentals & Investigations, Chapter 6
Whorls
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Whorls are divided into four groups:
plain, central pocket loop, double loop,
and accidental.
All whorl patterns have type lines and a
minimum of two deltas.
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Characteristics of Fingerprints
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Forensic Science: Fundamentals & Investigations, Chapter 6
Arches
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The plain arch is formed by ridges
entering from one side of the print,
rising and falling, and exiting on the
opposite side (like a wave).
The tented arch is similar to the plain
arch except that instead of rising
smoothly at the center, there is a sharp
upthrust or spike, or the ridges meet at
an angle that is less than 90 degrees.
Forensic Science: Fundamentals & Investigations, Chapter 6
Characteristics of Fingerprints
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Basic patterns can be further divided:
• Arch patterns:
4% plain
1% tented
• Whorl patterns:
2% central pocket
4% double loop
0.01% accidental
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Even twins have unique fingerprints
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Fingerprint Minutiae Patterns
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Primary Classification
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Fingerprint classification systems are
based on knowledge of fingerprint
pattern classes.
First, fingers are paired up, placing one
finger in the numerator of a fraction
and the other in the denominator.
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Fraction Set Up
R Index R Ring L Thumb L Middle L Little
R Thumb R Middle R Little L Index L Ring
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Classification cont…
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The presence or absence of the whorl
pattern is the basis for the
determination of the primary
classification.
Forensic Science: Fundamentals & Investigations, Chapter 6
Classification Cont…
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If a whorl pattern is found on any
finger of the first pair, it is assigned a
value of 16; on the second pair, an 8;
on the third pair, a 4; on the second
pair, a 2; and on the last pair, a 1.
Any finger having a loop or arch is
assigned a 0.
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After values for all 10 fingers are
obtained, they are totaled, and a 1 is
added to both the numerator and
denominator.
The fraction thus obtained is the
primary classification.
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Approximately 25% of the population
falls into the 1/1 category; that is, all
their fingers have either loops or
arches.
Forensic Science: Fundamentals & Investigations, Chapter 6
Types of Fingerprints
There are 3 types of prints that investigators
look for at crime scenes:
1. Visible fingerprints—visible prints transferred
onto smooth surfaces by blood or other liquids
2. Patent fingerprints—indentations left in soft
materials such as clay or wax
3. Latent fingerprints—made visible by dusting
with powders or the use of chemicals
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Fingerprint Forensic FAQs
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How are latent fingerprints collected?
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AFIS – Automated Fingerprint
Identification System
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The heart of AFIS technology is the
ability of a computer to scan and
digitally encode fingerprints so that
they can be subject to high-speed
computer processing.
Forensic Science: Fundamentals & Investigations, Chapter 6
Fingerprint Forensic FAQs
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Can fingerprints be erased?
Only temporarily; they will grow back if removed with chemicals
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Is fingerprint identification reliable?
Yes, but analysts can make mistakes
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Can computers perform matches in seconds?
No, but the FBI’s Integrated Automated Fingerprint Identification
System (IAFIS or AFIS) can provide a match in 2 hours
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The Future of Fingerprinting
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New scanning technologies
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Yield detail in minute patterns
Reduce analytical mistakes
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Analyze trace elements of objects on the skin
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Technologies that recognize patterns in
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Retina
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Face
Veins in your palm
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Forensic Science: Fundamentals & Investigations, Chapter 6
Preserving Prints
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If small enough – take whole item, take care
so print is not damaged during transport
A photograph must be taken before any
attempts at preservation are made.
Forensic Science: Fundamentals & Investigations, Chapter 6
Preserving Prints
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If large item can “lift” print using broad
adhesive tape
Tape placed on appropriately labeled card
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Must photograph all prints and surroundings.
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. . . . . . . . . . . . . . Summary . . . .
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Fingerprints have long been used for
identification, and in the mid-1800s were
recognized as unique to each person.
Three main groups include arches, whorls,
and loops.
Basic analysis includes looking for cores and
deltas and making a ridge count.
Forensic Science: Fundamentals & Investigations, Chapter 6
. . . . . . . . . . . . . . . . . Summary
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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