Physical Sciences Friction Ridge Examination Chapter 19 ©2010 Elsevier, Inc

Physical SciencesFriction Ridge Examination

Chapter 19

©2010 Elsevier, Inc.

• Fingerprints are the current leader in identification markers

• Recent court challenges have raised questions about the science behind friction ridge examination

INTRODUCTION


• 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

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• 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

THE NATURAL BORN CRIMINAL


• First known systematic use of fingerprint identification in U.S. occurred in 1902 in New York City– 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

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

FINGERPRINTING IN THE UNITED STATES

• Identification Division of FBI was established in 1924 as a national repository and clearinghouse for fingerprint recordso Civil Identification Section was

developed in 1933o Identification Division was renamed

the Criminal Justice Information Services Division in 1992


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


– 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



– 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:– 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





–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”

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

What’s a Friction Ridge Print Made of?


• 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

Collecting Prints at Crime Scene


– 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

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

FRICTION RIDGE PATTERN VISUALIZATION TECHNIQUES


– 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

PRESERVING PRINTS FOR 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

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



• 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



– 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



– 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%

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



• 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



• 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



– 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

Classification


– 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

HOW LONG DO FRICTION RIDGE PRINTS LAST?


– 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

ELIMINATION PRINTS


• 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

Automated Fingerprint Identification Systems (AFIS)


– Capabilities include:• Enhance an image to improve its quality• Compare crime scene fingerprints against known 10-

print 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



• Universal Latent Workstation is designed to help agencies enter data into the system and share it with other, previously incompatible systems



• 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

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

IDENTIFICATION


• Friction ridge examination is the preeminent method of individualization in forensic science

CHAPTER SUMMARY


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Physical Sciences Friction Ridge Examination Chapter 19 ©2010 Elsevier, Inc