Forensics FingerPrint Unit

What are fingerprints?

A fingerprint is an impression of the friction ridges found on the inner surface of a finger or a thumb.

Fingerprint details

1. Ridge patterns and the details in small areas of friction ridges are unique and never repeated.
2. Friction ridges develop on the fetus in their definitive form before birth.
3. Ridges are persistent throughout life except for permanent scarring.
4. Friction ridge patterns vary within limits which allow for classification.

Arch

LINE ENTERS & EXITS PATTERN AT DIFFERENT SIDES

NO DELTAS

Loop

ENTERS & EXITS FROM SAME SIDE
\*1 DELTA

Ridge count

\# of ridges between tip of core and tip of delta

Ulna and Radial Loops

Are hand dependent
● Ulnar loop - the loop opens toward the little finger.
● Radial loop - the loop opens toward the thumb

Whorl

SPIRAL’ PATTERN
\*2 DELTALS
\*MANY FORMS OF WHORLS

DOUBLE LOOP

2 LOOPS INTERTWINED
\*2 DELTAS

CENTRAL POCKET LOOP

EYE’ PATTERN IN CENTER OF THE PATTERN
\*2 DELTAS

WHAT MAKES ONE PERSON’S FINGERPRINT DIFFERENT FROM ANOTHER PERSON’S?

There are small patterns and designs that are present on the ridge pattern of your fingertips. These small differences make fingerprints unique.

Henry Classification system based on the WHORL pattern

1)Determine whorl patterns on set of prints

2)Assign given numbers to these fingers

3)Plug in assigned values into equations

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NUMBERS ASSIGNED: Fingers #1,2 = 16 Fingers #3,4 = 8 Fingers #5,6 = 4 Fingers #7,8 = 2
Fingers # 9,10 = 1
EQUATION =
(#’s assigned to even numbered fingers) +1 (#’s assigned to odd numbered fingers) +1

Therefore, a person with whorl patterns on all of their fingers would have a Primary Classification of 32

And a person with no whorl patterns on any of their fingers would have a Primary Classification of 1 1

These ratios are not to be reduced, they are to be left as calculated.

Three types of fingerprints at a crime scene:

1)Latent – Impressions caused by perspiration / oils on ridges
(not seen easily)
*Visualization depends on surface*

2)Visible Prints – Left when ridges have a colored substance on them
(blood, ink/paint, etc.)
3)Plastic Prints – Impression left in a soft material (clay, drying blood)
*Easy to find at a crime scene*

METHOD OF DEVLOPING FINGERPRINTS DEPENDS ON…

SURFACE THE PRINT IS ON
\*METHODS FOUND SUCCESSFUL BY DEVELOPER

Developing Latent Prints on Nonabsorbent Surfaces

Powder – Adheres to body oils & perspiration.
\-Usually grey, black powders; Other colors used depending on background.
\-Lifted with tape, placed on card.

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Superglue Fuming – Fumes adhere to the print and make it white.
\-Cyanoacrylate ester is the chemical that interacts with print
\-Superglue is heated to produce fume -Has worked on the interior of a car

Reflected UV Imagining System (RUVIS)

* UV light strikes print and reflects back to a viewer that is converts it to visible light.

Developing latent fingerprints on Absorbent Surfaces

Iodine Fuming – Iodine fumes combine
with fatty oils / water
\-Iodine sublimes (solid 􏰀 gas) -Not a permanent image

Ninhydrin – Chemical treatment that reacts with amino acids in perspiration.
\-Sprayed onto surface
\-Produces purple-blue print -Takes 1-2 hours to develop (heat
increases rate) & last for 24-48 hours

Silver-nitrate (Physical developer) – Solution reacts with print but washed
away any traces of protein left on print -Last resort for developers

Alternate Light Source (ALS) – Specific wavelength of light used to illuminate fingerprint.
\-Portable, easy to use
\-Used with chemical treatments

Preservation of prints

DUSTING & LIFTING PRINTS
\*Lightly dust in direction of ridge pattern \*Place lifting tape over print
\*Peal off and place on labeled card with
a color that contrasts powder

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DIGITAL IMAGING – Computer programs used to enhance photos of prints
\*Filters used to make print clearer (Grayscale, contrast, interference)
\*Colors can be differentiated (print on a dollar bill or colored background)
\*’Compare’ function – side-by-side comparison.

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Biometrics terms

• Biometrics is a form of human identification.
• Physiological biometrics uses physical traits such as fingerprints and hand, iris, retina, and facial scans to identify people.
• Behavioral biometrics identifies people through handwriting, voice, keystroke, and gait recognition.

History and important dates/people

• The first systematic attempt at personal identification was devised by a French police expert, Alphonse Bertillon.
• The Bertillon system relied on a detailed description (portrait parlé) of the subject, combined with full-length and profile photographs, and a system of precise body measurements called anthropometry.

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• In China, fingerprints were used to sign documents as early as 3,000 years ago.

• William Herschel used palm prints to sign contracts.

• Henry Fauld suggested in 1880 that skin ridge patterns could be important to identify criminals.

Fingerprinting history pt.1 Francis Galton

In 1892, Francis Galton published his classic textbook, Finger Prints.

• At Galton’s insistence, the British government adopted fingerprinting as a supplement to the Bertillon system.

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Fingerprinting history pt.2 Dr. Juan

Dr. Juan Vucetich devised a classification system still used in most Spanish-speaking countries.

Fingerprinting history pt. 3 Edward Henry

Sir Edward Henry devised another classification system used in most English-speaking countries.

What happened in 1903 and what system was used? Also how did the affect fingerprinting techniques?

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.

After the Will West incident, the use of fingerprinting was adopted by the New York City Civil Service Commission in 1901.
• American police began to be trained in fingerprinting by Scotland Yard representatives at the 1904 World’s Fair.
• After that, fingerprinting began to be used in earnest in all major U.S. cities.

What are fingerprints?

Fingerprints are skin ridges found on the palm side of the fingers and thumbs.

What are the basic principles underlying the use of fingerprints in criminal investigations?

1. A fingerprint is an individual characteristic because no two fingers have yet been found to possess identical ridge characteristics.
2. A fingerprint will remain unchanged during an individual’s lifetime.
3\. Fingerprints have general ridge patterns that permit them to be systematically classified.

Principle one of a fingerprint

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.
• It is the identity, number, and relative location of these minutiae that imparts individuality to a fingerprint.

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

Principle two of fingerprints

• 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 which is responsible for determining the form and pattern of the ridges on the surface of the skin.
• Once the dermal papillae develop in the human fetus, the ridge patterns will remain unchanged throughout life except to enlarge during growth.

• Each skin ridge is populated with pores leading to sweat glands, from which perspiration is deposited on the skin.
• 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).
• Prints deposited in this manner are invisible to the eye and are commonly referred to as latent fingerprints.

Principle three of fingerprints

• All fingerprints are divided into three classes based on 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.

What are Loops? part 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.

loop-type pattern has ridges entering from one side of the print, recurving, and exiting from the same side. These patterns resemble a lake.

What are whorls?

• Whorls are divided into four groups: plain, central pocket loop, double loop, and accidental.
• A plain whorl and a central pocket loop have at least one ridge that makes a complete circuit.

• The double loop is made up of two loops combined into one fingerprint.
• An accidental pattern either contains two or more patterns, or is a pattern not covered by the other categories. Hence, an accidental pattern may consist of a combination loop and plain whorl or loop and tented arch.

The different whorl types

Plain whorl. One or more ridges form a complete circle-like pattern around the center. These often look like a bull’s-eye.

Central pocket loop. Ridges form a loop pattern which go around the circle-like pattern in the center. These often look like a peacock eye.

Double loop whorl. Two separate loops are present in one impression. These often look like the symbol of yin and yang.

Accidental whorl. A mixture of two different types of patterns. These often look like an accident since several patterns are occupying the same space.

Arches

Arches, the least common of the three general patterns, are divided into two 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).

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.

Arch patterns

Plain arch. Ridges enter the impression, rise to the center, and exit the opposite side of the impression. These often resemble hills.

Tented arch. Ridges enter the impression, spike towards the center, and exit the opposite side of the impression. These often resemble a tent.

What is Ace-V? What does it stand for?

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


1. Analysis
2. Comparison: Compare the questioned print at 3
levels.
3. Identify
4. Verification: Examiner’s conclusion is confirmed by a second examiner.

ACE-V comparison steps

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

• The Henry system was built upon to create the FBI system of classifying fingerprints. • First, fingers are paired up, placing one finger in the numerator of a fraction and the other in the denominator. The fraction is the primary classification.

The presence or absence of the whorl is determined for each finger.
• 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.

After values for all 10 fingers are obtained, they are totaled, and a 1 is added to both the numerator and denominator.

• Approximately 25% of the population falls into the 1/1 category; that is, all their fingers have either loops or arches.

AFIS

• The Integrated Automated Fingerprint Identification System (IAFIS) is maintained by the FBI and is the premier fingerprint database, with nearly 750 million fingerprint images.

• Each state has its own AFIS (Automated Fingerprint Identification System).
• 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 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).

What are visible prints?

• 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. 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.

What are latent prints?

• Latent prints deposited on hard and nonabsorbent surfaces (for example, glass, mirror, tile, and painted wood) are preferably developed by the application of a powder.
• Prints on porous surfaces (that is, papers, cardboard, and cloth) generally require treatment with a chemical.

How to detect prints?

• A device called the Reflected Ultraviolet Imaging System (RUVIS) can aid in the detection of latent fingerprints, without chemicals or powder.

• Powders, available in a variety of colors, can be applied with a brush or magnetic wand, and adhere to the perspiration and/or body oils of the print.

• Iodine fuming involves heating iodine crystals, which creates vapors that combine with latent prints to make them visible.
– Iodine prints are not permanent and will fade, making it necessary to photograph the prints immediately.

• Ninhydrin is a chemical that reacts with trace amounts of amino acids present in latent prints to produce a purple-blue color.
• Physical developer is a silver nitrate-based reagent used to develop prints when other chemical methods are ineffective.
• Iodine fuming, ninhydrin, and physical developer are used on porous surfaces.

• Superglue is approximately 98 to 99 percent cyanoacrylate ester, a chemical that interacts with and visualizes a latent fingerprint.
• Superglue 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.
• Superglue fuming is used on nonporous surfaces.

• Fingerprints can also be illuminated by shining a laser onto the print that causes the perspiration to fluoresce.
• Fluorescence of fingerprints can be highly sensitive.

What do you do after detecting fingerprints?

• Once the latent print has been visualized, it must be permanently preserved for future comparison and for possible use as court evidence.

Preserving prints

• A photograph must be taken before any further attempts at preservation are made.

• If the object is small enough to be transported without destroying the print, it should be preserved in its entirety.
• 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.