Physical Sciences
Friction Ridge Examination
Chapter 19
©2010 Elsevier, Inc.
INTRODUCTION
• Fingerprints are the current leader in
identification markers
• Recent court challenges have raised questions
about the science behind friction ridge
examination
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THE NATURAL BORN CRIMINAL
• Lombroso’s theory of the criminal man
influenced criminal identification and
criminology
– Criminals were said to be identified by
unattractive characteristics
• Large jaws, large faces, long arms, low and narrow
foreheads, large ears, excess hair, darker skin,
insensitivity to pain and inability to blush
• Racial stereotyping
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THE NATURAL BORN CRIMINAL
• Lombroso’s theory sparked a search for real,
measurable traits that would identify criminals
– Bertillion devised a complex system of anthropometric
measurements, photographs and descriptions
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Called Bertillionage
Used to quantify the body
Complicated, involved process
Difficult to standardize and replicate
Imprecise objective definitions
– Bengal, India office eventually dropped use of
Bertillionage, except fingerprint component
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FINGERPRINTING IN THE
UNITED STATES
• First known systematic use of fingerprint
identification in U.S. occurred in 1902 in New
York City
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New York Civil Service Commission scandal
New York State Prison Department
New York State Hospital
United States Penitentiary in Leavenworth, Kansas
followed suite and developed a fingerprint bureau
– 1904 World’s Fair brought fingerprint technique more
notoriety
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FINGERPRINTING IN THE
UNITED STATES
• First U.S. criminal conviction using fingerprint evidence
occurred in Chicago in the case of Thomas Jennings
• International Association for Identification was formed
in 1915
• The Finger Print Instructor by Kuhne was published in
1916
• Identification Division of FBI was
established in 1924 as a national
repository and clearinghouse for
fingerprint records
o Civil Identification Section was
developed in 1933
o Identification Division was
renamed the Criminal Justice
Information Services Division in
1992
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WHAT ARE FRICTION RIDGES?
– Friction ridges appear on
palms, soles, and the ends of
fingers and toes
• All primates have arboreal
evolutionary heritage
• Ridges provide friction
between the grasping
mechanism and whatever it
grasps
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WHAT ARE FRICTION RIDGES?
– Friction ridges develop in utero
• Begin forming in the 9th or 10th week of fetal development
• Primary friction ridges develop deep in the dermal layer of the
skin
• At about 14 weeks of gestation, sweat glands and ducts begin
to form, proliferating from the primary friction ridges
• Primary friction ridges proliferate until about 15th or 17th
weeks of gestation
• Secondary friction ridges appear after proliferation of primary
friction ridges stop
• Secondary friction ridges develop from 17th to 24th weeks of
gestation
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WHAT ARE FRICTION RIDGES?
– Interface between epidermis and dermis provides
template for configuration of the friction ridges on the
surface
• Numerous factors affect patterning and arrangement of
friction ridges including:
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–
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Genetics
Environmental factors
Drugs
Disease
Shape of volar pad
– Friction ridges remain the same throughout life
• Scarring or other trauma to the epidermal-dermal margin
may alter the friction ridge area
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WHAT ARE FRICTION RIDGES?
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What’s a Friction Ridge Print Made of?
– A friction ridge print is representation of a
friction ridge pattern in some medium
– Patent prints are visible with the unaided
eye
• Some transferable material on the ridge
pattern
• Ridge pattern left in soft substrate with
“memory”
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What’s a Friction Ridge Print Made of?
– Latent prints require some sort of assistance to
make them visible
• Composed of the sweat and oils of the body that are
transferred from the ridge pattern to some substrate
where they persist for some time
• Most familiar visualizing techniques uses fingerprint
powder
– Colored, fluorescent or magnetic materials that are finely
ground
– Brushed lightly over a suspected print to produce contrast
between background and print
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Collecting Prints at Crime Scene
• Friction ridge prints can be left on a wide
variety of surfaces and may persist for quite
some time
• Can be obtained from a variety of surfaces
including: glass, painted surfaces, plastics,
ceramics, paper and books
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FRICTION RIDGE PATTERN
VISUALIZATION TECHNIQUES
– Visualization techniques may be physical, chemical
or optical enhancements
• Fingerprint powders create contrast between ridge
pattern and background
– May be black, white and other colors
» Color used is determine by background
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FRICTION RIDGE PATTERN
VISUALIZATION TECHNIQUES
• Fingerprint powders
– Applied with a soft fiberglass brush that has long, very
fine bristles
– Print is lifted with frosted or clear tape for mounting on a
contrasting background card
– Information about the print, where, when and how it was
lifted and by whom, is recorded on card
– Identifier for chain of custody is also recorded
• Three main types of lasers used to detect
fingerprints are: argon, copper vapor, and Nd:YAG
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PRESERVING PRINTS FOR ANALYSIS
– Friction ridge prints should be photographed
when they are found at the crime scene or at the
laboratory
• Requires skill in various methods of lighting, exposure,
filters, and latent print enhancement
• Final image should be a 1:1 print to facilitate the
eventual comparison
• If surface is difficult to process, it should be submitted
to the laboratory for examination
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PRINCIPLES OF
FRICTION RIDGE ANALYSIS
• Galton was the first to scientifically study fingerprints
– Developed classification system for common fingerprint
patterns that is still is use today
• Friction ridges are considered unique
• Galton attempted to calculate the likelihood of finding two
friction ridge patterns that are the same
• All similar calculations indicate that the probability of any
one fingerprint is between 0.000000954 and 1.2 × 10−80
– Considered unique by the vast majority of forensic scientists and
the courts
– More similarities between two prints leads to a lower
probability of false positives
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PRINCIPLES OF
FRICTION
RIDGE
ANALYSIS
Friction ridges are studied for the kind, number and
location of various ridge characteristics or minutiae
– Arrangement of characteristics create one-of-a-kind
pattern
– Careful point-by-point study determines if enough
significant minutiae present in the known print are present
in the questioned print
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PRINCIPLES OF FRICTION RIDGE
ANALYSIS
• Majority of prints are identified, resolved and
compared are partial prints
– Only a portion of the complete print pattern is
represented
– Scientist must determine if sufficient information
is present to make a proper comparison
• Prints may be unidentifiable due to smudging,
graininess, or size
• Dependent upon scientist’s experience, visual acuity,
and judgment
©2010 Elsevier, Inc.
PRINCIPLES OF FRICTION RIDGE
ANALYSIS
– Forensic scientists debate how many points of comparison
are necessary and sufficient to reach a conclusion of
identification
• Point counting standard dictated how many points of comparison
were required before a positive conclusion could be reached
– Varied from 8 to 20
– No statistical basis for such numbers
• Most agencies use a “no-point” standard
– Threshold is one of a sufficient number of characteristics necessary to
make a conclusion of identification, however many that might be
» Experience and judgment are central to the process of a quality
examination
» Requires proper training and practical experience
» Experts must be able to articulate and support their findings
©2010 Elsevier, Inc.
Classifying Fingerprints
– General patterns of friction ridges allow for their
classification and organization
– Fingerprints are divided into three classes: loops,
arches, and whorls
– Relative appearance of loops is 60-65%, whorls
30-35% and arches 5%
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Classifying Fingerprints
• Loops have one or more ridges entering from
one side of the print, curving back on
themselves and exiting the fingertip on the
same side
– A loop that enters and exits on the side of the finger
toward the little finger is called an ulnar loop
– A loop that enters and exits on the side toward the
thumb is called a radial loop
– Loops are surrounded by two diverging ridges called
type lines
– The point of divergence is called the delta
– The central portion of the loop is called the core
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Classifying Fingerprints
• Arches are the rarest of the three main classes or
patterns
– A plain arch has ridges that enter from one side of the finger,
gradually rise to a rounded peak and exit the other side
– A tented arch is a pronounced, sharp peak
– Arches do not have type lines, cores or deltas
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Classifying Fingerprints
• Whorls are subdivided into several classes
– A plain whorl is located between two deltas of the
whorl pattern and has a minimum of one ridge that is
continuous around the pattern
– A central pocket loop is not located between two
deltas of the whorl pattern and has a minimum of
one ridge that is continuous around the pattern
– A double loop is made up of two loops that swirl
around each other
– An accidental is a pattern that combines two or more
patterns, excluding the plain arch, and/or does not
clearly meet the criteria for any of the other patterns
– All whorls have type lines and at least two deltas
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Classification
– Based on Henry system
– Modern fingerprint classification consists of a primary classification
that encodes fingerprint pattern information into two numbers
• Arches and loops are given a value of zero
• Whorls are given a number depending on which finger they appear
• Values are summed and the resulting primary classification is displayed like a
fraction
• Considered class evidence
– Comparison of minutiae and higher level details is only method for
fingerprint identification
– Drawbacks include:
• Rarely are full sets of prints found at a crime scene
• Time consuming
• Error prone
©2010 Elsevier, Inc.
HOW LONG DO
FRICTION RIDGE PRINTS LAST?
– Plastic prints remain as long as the impressed
material is structurally intact
– Prints left in a medium, such as blood or dust, are
fragile and do not last long
– Latent prints, in a proper environment, can last for
years
– Age of prints is almost impossible to determine
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ELIMINATION PRINTS
– Elimination prints can eliminate individuals from
an investigation’s focus, demonstrate proper
scientific mindset, create confidence in the mind
of the trier-of-fact
• Displaying what is and what is not a match clarify
process of identification and comparison
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Automated Fingerprint Identification
Systems (AFIS)
• Process of capturing, storing, searching and
retrieving fingerprints via computer is now a
standard occurrence
• Automated fingerprint identification systems
(AFIS) are computerized databases of digitized
fingerprints that are searchable through software
• Integrated Automated Fingerprint Identification
System, IAFIS, was developed to ease the
exchange of information between systems
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Automated Fingerprint Identification
Systems (AFIS)
– Capabilities include:
• Enhance an image to improve its quality
• Compare crime scene fingerprints against known 10print records retrieved from the database
• Search crime scene fingerprints against known
fingerprints when no suspects have been developed
• Automatically search the prints of an arrestee against a
database of unsolved cases
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Automated Fingerprint Identification
Systems (AFIS)
• Universal Latent Workstation is designed to
help agencies enter data into the system and
share it with other, previously incompatible
systems
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IDENTIFICATION
• Final identification decision in fingerprint
comparison is reached when sufficient quality
and quantity of Level 1, 2, and 3 friction ridge
details are present
– Level 1 detail includes the general ridge flow and
pattern configuration
• Not sufficient for identification
• Information may include orientation, core and delta
location, and distinction of finger versus palm
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IDENTIFICATION
– Level 2 detail includes formations, defined as ridge
endings, bifurcations, dots or combinations of
these features
• Sufficient for identification
– Relationship of these features enables individualization
– Level 3 detail includes all attributes of a ridge,
such as ridge path deviation, width, shape, pores,
edge contour, incipient ridges, breaks, creases,
scars, and other permanent minutiae
• Sufficient for identification
©2010 Elsevier, Inc.
CHAPTER SUMMARY
• Friction ridge examination is the preeminent
method of individualization in forensic science
©2010 Elsevier, Inc.