Forensics Chapter 6 Fingerprints

History (1 of 5)

• The first systematic attempt at personal identification was

devised by a French police expert, Alphonse Bertillion.

• The Bertillion system relied on a detailed description of the

subject, combined with full-length and profile photographs and a

system of precise body measurements called anthropometry.

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History (2 of 5)

• In 1892 Francis Galton published his classic textbook Finger

Prints.

• At Galton's insistence, the British government adopted

fingerprinting as a supplement to the Bertillion system.

• The next step was the creation of classification systems capable

of filing many thousands of prints in a logical and searchable

sequence.

History (3 of 5)

• Dr. Juan Vucetich devised a classification system still used in

most Spanish-speaking countries, while Sir Edward Henry

devised another classification system used in most English-

speaking countries.

History (4 of 5)

• In 1903, when the Bertillion system could not distinguish

between two men (one Will West and the other William West), it

was fingerprinting that clearly distinguished them.

History (5 of 5)

• After the Will West incident, the use of fingerprinting by the New

York City Civil Service Commission in 1901, and the training of

American police by Scotland Yard representatives at the 1904

World's Fair, fingerprinting began to be used in earnest in all

major U.S. cities.

Fingerprint Principles (1 of 3)

• Fingerprints are a reproduction of friction skin ridges found on

the palm side of the fingers and thumbs.

Fingerprint Principles (2 of 3)

• The basic principles underlying the use of fingerprints in criminal

investigations are that:

– A fingerprint is an individual characteristic because no two

fingers have yet been found to possess identical ridge

characteristics;

Fingerprint Principles (3 of 3)

• The basic principles underlying the use of fingerprints in criminal

investigations are that:

– A fingerprint will remain unchanged during an individual's

lifetime; and

– A fingerprints have general ridge patterns that permit them

to be systematically classified.

Principle One (1 of 5)

• Mathematically, the probability for the existence of two identical

fingerprint patterns in the world's population is extremely small.

Galton calculated the existence of 64 billion different

fingerprints.

– Besides theoretical calculations, of the millions upon millions

of individuals who have had their prints classified, no two

fingerprints have been found to be identical.

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Principle One (2 of 5)

• Mathematically, the probability for the existence of two identical

fingerprint patterns in the world's population is extremely small.

Galton calculated the existence of 64 billion different

fingerprints.

– The individuality of a fingerprint is not determined by its

general shape or pattern, but by the careful study of its ridge

characteristics, known as minutiae.

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Principle One (3 of 5)

• Mathematically, the probability for the existence of two identical

fingerprint patterns in the world's population is extremely small.

Galton calculated the existence of 64 billion different

fingerprints.

– It is the identity, number, and relative location of these

minutiae that imparts individuality to a fingerprint.

Principle One (4 of 5)

• Some common fingerprint ridge characteristics are bifurcations,

ridge endings, ridge dots, and enclosures.

– There are as many as 150 minutiae on the average finger.

– Currently in the United States, there is no predetermined

minimum number of friction ridge characters which must be

present in two impressions in order to establish positive

Identification.

Principle One (5 of 5)

• Some common fingerprint ridge characteristics are bifurcations,

ridge endings, ridge dots, and enclosures.

– In a judicial proceeding, an expert must demonstrate a

point-by-point comparison in order to prove the identity of an

individual.

Principle Two (1 of 4)

• The epidermis is the outer layer of the skin, while the dermis is

the inner layer of the skin.

• The dermal papillae is the layer of cells between the epidermis

and dermis, that is responsible for determining the form and

pattern of the ridges on the surface of the skin.

Principle Two (2 of 4)

• Once the dermal papillae develop in the human fetus, the ridge

patterns will remain unchanged throughout life except to enlarge

during growth.

Principle Two (3 of 4)

• Each skin ridge is populated with pores leading to sweat glands,

from which perspiration is deposited on the skin.

Principle Two (4 of 4)

• Once the finger touches a surface, perspiration, along with oils

that may have been picked up by touching the hairy portions of

the body, is transferred onto that surface, leaving the finger's

ridge pattern (a fingerprint). Pints deposited in this manner are

invisible to the eye and are commonly referred to a latent

fingerprints.

Principle Three

• All fingerprints are divided into three classes on the basis of

their general pattern: loops, arches, and whorls (L.A.W.).

• 60-65% of the population have loops, 30-35% have whorls, and

about 5% have arches.

Loops (1 of 2)

• A loop must have one or more ridges entering from one side of

the print, recurving, and exiting from the same side.

– 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.

Loops (2 of 2)

• The pattern area of the is surrounded by two diverging ridges

known as type lines.

• The ridge point at or nearest the point where two type lines

diverge is known as the delta. All loops must have one delta.

• The approximate center of the loop pattern is known as the

core.

• All loops must have one delta, which is the ridge point at or

directly in front of the point where two ridge lines (type lines)

diverge.

Whorls (1 of 3)

• 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.

Whorls (2 of 3)

• A plain whorl and a central pocket loop have at least one ridge

that makes a complete circuit.

– If an imaginary line drawn between the two deltas within

these patterns touches any of the circular ridges, the pattern

is a plain whorl. If no such ridge is touched, the pattern is a

central pocket loop.

Whorls (3 of 3)

• The double loop is made up of two loops combined into one

fingerprint.

• An accidental either contains two or more patterns, or is a

pattern not covered by the other categories. Hence, an

accidental may consist of a combination loop and plain whorl or

loop and tented arch.

• 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.

Arches (1 of 2)

• Arches, the least common of the three general patterns, are

divided into two distinct groups: plain arches and tented arches.

• 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).

Arches (2 of 2)

• 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.

• Arches do not have type lines, deltas, or cores.

• Arches do not have type lines, deltas, or cores.

ACE-V (1 of 2)

• A four-step process to identify and individualize a finger print:

– Analysis

– Comparison: compare the questioned print at (3) levels.

– Identify

– Verification: examiner's conclusion is confirmed by a second

examiner.

ACE-V (2 of 2)

• Level 1 encompasses the general ridge flow and pattern

configuration.

• Level 2 includes locating and comparing ridge characteristics or

minutiae.

• Level 3 includes the examination and location of ridge pores,

breaks, creases, scars, and other permanent minutiae.

Primary Classification (1 of 6)

• 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.

Primary Classification (2 of 6)

• The presence or absence of the whorl pattern is the basis for

the determination of the primary classification.

Primary Classification (3 of 6)

• 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.

Primary Classification (4 of 6)

• 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.

Primary Classification (5 of 6)

• Approximately 25% of the population falls into the 1/1 category;

that is, all their fingers have either loops or arches.

Primary Classification (6 of 6)

• A fingerprint classification system cannot in itself unequivocally

identify an individual; it will merely provide the fingerprint

examiner with a number of candidates, all of whom have an

indistinguishable set of prints in the system's file.

AFIS (1 of 4)

• 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.

AFIS (2 of 4)

• AFIS aids in classifying and retrieving fingerprints by converting

the image of a fingerprint into digital minutiae that contain data

showing ridges at their points of termination (ridge endings) and

their branching into two ridges (bifurcations).

AFIS (3 of 4)

• When the search is complete (a computer can make thousands

of comparisons per second), the computer produces a list of file

prints that must be examined by a trained fingerprint expert.

AFIS (4 of 4)

• AFIS systems come in all sizes allowing for the creation of local

systems at the country and city levels.

• Software incompatibilities often mean that state and local AFIS

systems cannot communicate with each other and share

information.

• In 2014, the FBI integrated its IAFIS system into the NGI

system.

Latent Prints

• Once the finger touches a surface, body perspiration and/or oils

present on the finger ridges are transferred to that surface,

leaving an impression.

• Prints deposited in this manner are invisible to the eye and are

commonly referred to as latent or invisible fingerprints.

Visible Prints (1 of 2)

• Visible prints are made when fingers touch a surface after the

ridges have been in contact with a colored material such as

blood, paint, grease, or ink.

• Plastic prints are ridge impressions left on a soft material, such

as putty, wax, soap, or dust.

Visible Prints (2 of 2)

• Locating visible or plastic prints at the crime scene normally

presents little problem to the investigator, because these prints

are usually distinct and visible to the eye.

Detecting Prints on Non-Porous

Surfaces (1 of 7)

• Latent prints deposited on hard and nonabsorbent surfaces

(e.g., glass, mirror, tile, and painted wood) are preferably

developed by the application of a powder; whereas prints on

porous surfaces (e.g., papers, cardboard, and cloth) generally

require treatment with a chemical.

Detecting Prints on Non-Porous

Surfaces (2 of 7)

• Powders, available in a variety of colors, can be applied with a

brush or magnetic wand, and adhere to perspiration and/or body

oils of the print. Most common are black powders (black carbon)

and gray powders (aluminum dust).

Detecting Prints on Non-Porous

Surfaces (3 of 7)

• Super Glue is approximately 98 to 99 percent cyanoacrylate

ester, a chemical that actually interacts with and visualizes a

latent fingerprint.

Detecting Prints on Non-Porous

Surfaces (4 of 7)

• Super Glue fuming develops latent prints on nonporous

surfaces, such as metals, electrical tape, leather, and plastic

bags.

– Development occurs when fumes from the glue adhere to

the print, usually producing a white latent print.

Detecting Prints on Non-Porous

Surfaces (5 of 7)

• Super Glue  fuming can be accomplished by using either a

fuming chamber (for up to six hours) or a handheld wand that

heats a small cartridge containing cyanoacrylate.

Detecting Prints on Non-Porous

Surfaces (6 of 7)

• Fingerprints are treated with chemicals that would induce

fluorescence when exposed to lasers or high-intensity light

sources ("alternate light sources") such as quartz halogen,

xenon arc, or indium arc light sources.

Detecting Prints on Non-Porous

Surfaces (7 of 7)

• Dye combinations known as RAM, RAY, and MRM 10, when

used in conjunction with Super Glue fuming, have been effective

in visualizing latent fingerprints by fluorescence.

Detecting Prints on Porous Surfaces

(1 of 5)

• Examiners use various chemical methods to visualize latent

prints on porous surfaces, such as iodine fuming, ninhydrin, and

Physical Developer.

Detecting Prints on Porous Surfaces

(2 of 5)

• Iodine fuming involves heating iodine crystals that cause vapors

which combine with latent prints to make them visible.

– Iodine prints are not permanent and will fade, making it

necessary to photograph the prints immediately.

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Detecting Prints on Porous Surfaces

(3 of 5)

• Ninhydrin reacts chemically with trace amounts of amino acids

present in latent prints to produce a purple-blue color. It's the

chemical method of choice.

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Detecting Prints on Porous Surfaces

(4 of 5)

• Physical Developer is a silver-nitrate-based reagent used to

develop prints when other chemical methods are ineffective. It is

also useful for developing prints on porous objects that may

have been wet at one time.

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Detecting Prints on Porous Surfaces

(5 of 5)

• If one wants to use all of the three chemical methods on the

same surface, it is necessary to first fume with iodine, then treat

with ninhydrin, and then apply physical developer.

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Preserving Prints (1 of 2)

• If the object is small enough to be transported without

destroying the print, it should be preserved in its entirety.

• A photograph must be taken before any attempts at

preservation are made.

Preserving Prints (2 of 2)

• Prints on large immovable objects that have been developed

with a powder can best be preserved by "lifting" with a broad

adhesive tape.

• Then the tape is placed on a properly labeled card that provides

a good background contrast with the powder.

Digital Imaging (1 of 2)

• Digital imaging is the process by which a picture is converted

into a digital computer file.

• With the help of digital imaging software, fingerprints, which are

often not in perfect condition, can now be enhanced for the most

accurate and comprehensive analysis.

Digital Imaging (2 of 2)

• An important and useful tool, especially for fingerprint

identification, is the "compare" function that places two images

side by side and allows the examiner to chart the common

features on both images simultaneously.