Fingerprints Forensic Biology

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FINGERPRINTS

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History

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The first systematic attempt at personal identification wasdevised 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.

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.


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History

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Dr. Juan Vucetich devised a classification system still used inmost Spanish-speaking countries, while Sir Edward Henry

devised another classification system used in most English-

speaking countries.


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Dr. Juan Vucetich

In 1892, two children were found brutally murdered in their home in

Argentina. The 27-year-old mother, Francisca Rojas, also had her throat cut.

Police looked into her neighbor Pedro Ramón Velázquez., but he had an alibi,

having been out with several friends at the time of the murders.

A bloody print was found on a door post. Remembering the training he

received from Juan Vucetich, Police Inspector Alvarez removed the section ofthe door with the impression and then requested Rojas be fingerprinted.

He compared the impression on the door to that of Rojas and matched it to

her. When confronted with this evidence, Rojas broke down and confessed to

the murders. Rojas' boyfriend had been overheard saying he would marry her

"except for those two brats". As a result of the Rojas murders, Argentina became the first country in the

world to abolish anthropometry and file its criminal records based solely on

fingerprint classification. Vucetich's classification system is still used in many

South American countries today.

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History

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In 1903, when the Bertillion system could not distinguishbetween 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 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.


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Fingerprint Principles

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Fingerprints are a reproduction of friction skinridges found on the palm side of the fingersand thumbs.

The basic principles underlying the use of

fingerprints in criminal investigations are that: (1) a fingerprint is an individual characteristic because no

two fingers have yet been found to possess identical ridgecharacteristics;

(2) a fingerprint will remain unchanged during an individual’slifetime; and

(3) fingerprints have general ridge patterns that permit them

to be systematically classified.


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Fingerprint ridge characteristics.

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A fingerprint exhibit illustrating the matching ridge

characteristics between the crime-scene print and an

inked impression of one of the suspect’s fingers.

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Principle One

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Mathematically, the probability for the existence of twoidentical fingerprint patterns in the world’s population isextremely small.

Besides theoretical calculations, of the millions upon millionsof individuals who have had their prints classified, no two

fingerprints have been found to be identical. The individuality of a fingerprint is not determined by its

general shape or pattern, but by the careful study of itsridge characteristics, known as minutiae.

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

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


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Types of minutiae

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Principle One

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After a three year study, it was determined that “novalid basis exists for requiring a predeterminedminimum number of friction ridge characters whichmust be present in two impressions in order toestablish positive identification.”

In a judicial proceeding, an expert must demonstratea point-by-point comparison in order to prove theidentity of an individual.


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Principal Two

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The epidermis is the outer layer of the skin, while thedermis is the inner layer of the skin.

The dermal papillae is the layer of cells between theepidermis and dermis, that is responsible for

determining the form and pattern of the ridges onthe 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. Thus, afingerprint will remain unchanged during anindividual’s lifetime.


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Cross-section of human skin.

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Principle Two

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Each skin ridge is populated with pores leading tosweat 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 touchingthe hairy portions of the body, is transferred onto

that surface, leaving the finger’s ridge pattern (a

fingerprint).


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Principle Three

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All fingerprints are divided into three classes on the basisof their general pattern: loops, arches, and whorls (L.A.W.)


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Principle Three

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A loop must have one or more ridges entering fromone side of the print, recurving, and exiting from thesame side.


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Principle Three

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If the loop opens toward the littlefinger, it is called an ulnar loop.

If the loop opens toward the thumb,it is called a radial loop.

Delta

L – Radial Loop

R - Ulnar Loop L – Ulnar Loop

R - Radial Loop


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Principle Three

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All loops must have one delta, which is the ridge point ator directly in front of the point where two ridge lines(type lines) diverge.


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Principle Three

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Whorls are divided into four groups: plain, centralpocket loop, double loop, and accidental.

All whorl patterns have type lines and a minimum oftwo deltas.

A plain whorl and a central pocket loop have at leastone ridge that makes a complete circuit.


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Principle Three

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Draw a line between the two deltas in the plain andcentral pocket whorls. If some of the curved ridgestouch the line, it is a plain whorl. If none of thecenter core touches the line, it is a central pocketwhorl.

Plain

Whorl

Central

PocketWhorl


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Principle Three

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The double loop is made up of two loops combinedinto one fingerprint.

An accidental either contains two or more patterns,or is a pattern not covered by the other categories.

Delta

Delta

Double Loop Whorl Accidental


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Principle Three

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Arches, the least common of the three generalpatterns, are divided into two distinct groups: plainarches and tented arches.

The plain arch is formed by ridges entering from one

side of the print, rising and falling, and exiting on theopposite side (like a wave).


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Principle Three

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The tented arch is similar to the plain arch exceptthat instead of rising smoothly at the center, there is asharp upthrust or spike, or the ridges meet at anangle that is less than 90 degrees.

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


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Latent Prints

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Once the finger touches a surface, body perspirationand/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 invisiblefingerprints.


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Visible Prints

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Visible (patent) prints are made when fingerstouch a surface after the ridges have been incontact with a colored material such as blood,paint, grease, or ink.

Plastic prints are ridge impressions left on asoft material, such as putty, wax, soap, or dust.

Locating visible or plastic prints at the crimescene normally presents little problem to the

investigator, because these prints are usuallydistinct and visible to the eye.


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Latent Prints

Once located, the crime scene investigator candevelop the print in the most appropriate fashion.

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.

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Porous Surfaces

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Types of Evidence Paper items

Cardboard

Unfinished wood Examiners use various chemical methods to visualize

latent prints on porous surfaces, such as iodinefuming, ninhydrin, and Physical Developer.


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Porous Evidence

Processing Techniques 1,2-Indanedione (IND)

Ninhydrin (NIN)

1,8-Diazafluoren-9-One (DFO)

Oil Red O (ORO) Iodine Fuming (IF)

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IND NIN IFORO


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Detecting Prints

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Ninhydrin reacts chemically with trace amounts ofamino acids present in latent prints to produce apurple-blue color.


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Non-Porous Evidence

Types of Evidence Plastic

Glass

Metal

Non-adhesive side of tape

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Non-Porous Evidence

Processing Techniques Cyanoacrylate Ester

Superglue (SG)

Powders

Black, magnetic, fluorescent

Fluorescent Dye Stain

Rhodamine 6G (R6G)

RAM

Amido Black

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Detecting Prints

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Powders, available in a variety of colors, can beapplied with a brush or magnetic wand, and adhere toperspiration and/or body oils of the print.

Super Glue® fuming develops latent prints onnonporous 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.


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Detecting Prints

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Super Glue® is approximately 98 to 99 percentcyanoacrylate ester, a chemical that actually interactswith and visualizes a latent fingerprint.

Super Glue fuming can be accomplished by usingeither a fuming chamber (for up to six hours) or a

handheld wand that heats a small cartridge containingcyanoacrylate.


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Amido Black

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Detecting Prints

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The high sensitivity of fluorescence serves as theunderlying principle of many of the new chemicaltechniques used to visualize latent fingerprints.

Fingerprints are treated with chemicals that wouldinduce fluorescence when exposed to lasers, or high-

intensity light sources (“alternate light sources”) suchas quartz halogen, xenon arc, or indium arc lightsources.


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Detecting Prints

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Once the latent print has been visualized, it must bepermanently preserved for future comparison and forpossible use as court evidence.

A photograph must be taken before any further

attempts at preservation are made.


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Transporting Prints

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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.


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Digital Imaging

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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.


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Comparison

3 Levels of Detail: Level 1: Overall Ridge flow, pattern types

Level 2: Ridge paths, minutiae

Level 3: Size and shapes of pores and ridges,

incipient ridges, scars

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Comparison- Level 1

Overall ridge flow, pattern Arches: plain & tented (5%)

Whorls: plain, central pocket loop, double loop, accidental (30-35%) Loops : radial & ulnar (60-65%)

Exclusions can occur at this level

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Comparison-Level 2

Individual ridge path, minutiae Different degrees of rarity in minutiae

Identification occurs at this level

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Comparison-Level 3

Ridge shape - ridge width and shape, pores, edge contour,

incipient ridges, creases, scars

Can support ID’s

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Evaluation

Look at all the information between the latent print and

known print

Quality and quantity of similarities or differences to render a

conclusion

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Verification

All latent print identifications areindependently examined by another

competent latent print examiner (ACE)

Verification/2nd Verification

Blind Verification

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IAFIS

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AFIS

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The heart of AFIS technology is the ability of acomputer to scan and digitally encode fingerprints sothat they can be subject to high-speed computerprocessing.

AFIS aids in classifying and retrieving fingerprints by

converting the image of a fingerprint into digitalminutiae that contain data showing ridges at theirpoints of termination (ridge endings) and theirbranching into two ridges (bifurcations).

When the search is complete (a computer can makethousands of comparisons per second), the computerproduces a list of file prints that must be examined by atrained fingerprint expert.


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IAFIS

Not only fingerprints, but corresponding criminal histories;

mug shots; scars and tattoo photos; physical characteristics like

height, weight, and hair and eye color; and aliases.

The system also includes civil fingerprints, mostly of individuals

who have served/are serving in the U.S. military or have been

or are employed by the federal government.

In the summer of 2014, IAFIS was replaced by Next

Generation Identification program (NGI) which provides

automated fingerprint and latent search capabilities, electronic

image storage, and electronic exchange of fingerprints to morethan 18,000 law enforcement agencies and other authorized

criminal justice partners 24 hours a day, 365 days a year.

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Comparison

ACE-V Analysis

Comparison

Evaluation

Verification

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Questions?

Documents

Fingerprints Forensic Biology