Methods of Identification
Presumptive vs. Positive
ID
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Personal viewing of victim
Fingerprints
Dental records
Radiographs and anthropology
DNA analysis
Facial/photo superimposition
Scars, marks, tattoos, etc.
Personal effects
– Clothing, body artifacts
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Environment
Fingerprinting
History
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1880- Dr. Henry Faulds
– First used fingerprints at a crime scene to ID the
perpetrator
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1892- Sir Francis Galton
– Published first textbook “Fingerprints”
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1897- Sir Edward Henry
– Proposed a classification system adopted by Scotland Yard
– System still widely used
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1910– Accepted by US as a method of identification
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1930– FBI set up National fingerprint file
What is a fingerprint?
Layers of
the Skin
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Epidermis
Dermis
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Hypodermis
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Dermis - Papillary layer
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Superficial, ~20% of
dermis
Dermal papillae form
ridges on hands and
feet to increase friction
Dermis - Reticular layer
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Deeper, thick layer
Flexure lines – dermal
infoldings at wrist,
palms, knees, etc. to
secure skin to deep
tissue
Eccrine sweat glands primarily for
thermoregulation
Sebaceous glands - oil
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Develop in utero ~13-15 weeks of
gestation
Ridges are unique and permanent
The patterns never changes except in
size
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Print left by secretions from pores in
the ridges
18 major components
– Primarily water, amino acids + salts
– Some oils
General features of all
prints
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Ridges / ridge
lines – raised
part of the skin,
~150 per finger
Furrows –
lowered skin
Minutiae – small,
unique ridge
characteristics
Delta – point
where 3 ridge
lines meet in a
triangle
Core – center of
the fingerprint
General classifications
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Loops
– 60-70% of the population
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Whorls
– 25-35%
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Arches
– 5%
Loops
One or more of the ridges
enters on one side of the
impression 
recurves 
touches or crosses the line
running from the delta to
the core 
and terminates one the same
side where the ridges
entered
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There is one delta.
The number of ridge lines
forming the loop is an
identifying characteristic too
Types of loops
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Two bones in the
lower arm
Radius - attaches to
wrist/hand closest to
the thumb
Ulna – attaches
closest to little finger
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Radial loop
– Ridge lines enter/exit on the side of the
finger pointing towards the thumb
– Not common
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Ulnar loop
– Ridge lines enter/exit on the side of the
finger pointing towards the little finger
Whorls
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2 or more deltas
Types of Whorls
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Plain whorl
Consists of one or more ridges
which make or tend to make a
complete circuit, with 2 deltas
If an imaginary line is drawn
between deltas, there is at least
one recurving ridge within the
inner pattern area that is cut or
touched.
At least one type line forms a
circle
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Central pocket whorl
Consists of one or a few
ridges which make or tend to
make a complete circuit, with
2 deltas
If an imaginary line is drawn
NO recurving ridges within the
inner pattern are cut or
touched.
At least one type line forms a
circle
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Double loop whorl
Consists of two
separate and distinct
loop formations with
two separate and
distinct shoulders and
two deltas.
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Accidental whorl
Contains 3 or more
deltas
Arches
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Ridges run from one side to the other,
making no backward turn.
Generally there is no delta + no
significant core
If there is a delta recurving ridge must
intervene between the core and delta
points.
Types of arches
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Plain arch
The overall pattern
area tends to just
flow through the
print with no
significant changes
Types of arches
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Tented arch
Contains a
significant upthrust
Composites
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Include
patterns in
which
combinations
of the tented
arch, loop
and whorl are
found in the
same print
Fingerprint ID Practice
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Assume prints are from the left hand
A
D
B
E
C
F
Plain whorl
Plain arch
Ulnar loop
Central pocket whorl
Tented arch
Double loop whorl
Minutiae
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Unique identifying points
FBI requires 8 for a positive ID
– Ranges from 5-12 in different states
Types of minutiae
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Ridge ending
Bifurcation/
Trifurcation
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Dot
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Island
– Ridge line
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Lake
– Enclosure
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Crossover
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Bridge
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Ellipse
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Spur
Fingerprint ID techniques
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1. Take a tenprint
– ID general
classification for
each finger
Fingerprint ID techniques
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2. Balloon print of right index finger
– ID general classification
– ID as many different types of minutiae as
possible
Types of prints found in
the environment
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Latent
– Formed by oil + sweat deposited by a person’s
fingers when they touch a surface
– Invisible to the naked eye, must be developed
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Visible
– Prints contaminated with blood, ink, etc. that
leave visible prints
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Plastic (molded)
– Impression left in a soft substance (i.e. soap,
wax)
Latent print detection
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1. Dusting powders
– Normal
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Grey vs. black
– Magnetic
– Fluorescent
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Good for hard or nonabsorbent surfaces
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2. Cyanoacrylate
fuming
Turns a latent print
into a permanent
visible print (arrested
print)
Good for plastics +
metals
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3. Iodine fuming
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Good for paper
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4. Ninhydrin
spray
Good for
paper, reacts
with amino
acid residues
in sweat
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5. Silver nitrate (physical developers)
Good for porous surfaces like currency,
wood + cardboard, recognizes lipids
Methods of Comparison
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Henry Primary Classification System
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Calculate the value given the following equation:
Pair #
1
2
3
4
5
R. Index + R. Ring + L. Thumb + L. Middle + L. Little + 1
R. Thumb + R. Middle + R. Little + L. Index + L. Ring + 1
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Numerical value assigned to any WHORL in
the numerator or denominator
Pair 1 = 16
Pair 2 = 8
Pair 3 = 4
Pair 4 = 2
Pair 5 = 1
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ARCHES and LOOPS = 0
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Example
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Whorls ID’d in right index and left index
fingers
Arches or loops everywhere else
What is the Primary Classification value?
Remember:
R. Index + R. Ring + L. Thumb + L. Middle + L. Little + 1
R. Thumb + R. Middle + R. Little + L. Index + L. Ring + 1
Example
R. Index + R. Ring + L. Thumb + L. Middle + L. Little + 1
R. Thumb + R. Middle + R. Little + L. Index + L. Ring + 1
16 + 0 + 0 + 0 + 0 + 1 = 17
0+0+0+2+0+1 = 3
AFIS – Automated fingerprint identification
system
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Computer scanners identify ridge endings
and bifurcations only, and their relative
positions are mapped
Prints lifted at the crime scene are
compared to fingerprints on file
A group of suspect fingerprint cards is
identified
An examiner does a point by point
comparison
The computer can compare the suspect's
print to 500,000 fingerprint cards in less
than a second
Computer enhancement can also
compensate for imperfections in lifted latent
prints