Fingerprints Chapter 14 Criminalistics. History of Fingerprinting –First systematic attempt at...

transcript

FingerprinFingerprintsts

Chapter 14Criminalistics

History of History of FingerprintingFingerprinting

– First systematic attempt at personal identification•Alphonse Bertillon in 1883

– Anthropometry: system of precise body measurements

• Included detailed descriptions of the subject

• Full-length and profile photographs• Accuracy of measurements were

disproved by the William West Case

History of FingerprintingHistory of Fingerprinting

• Francis Galton– 1892: Published Finger Prints

• Described the anatomy of fingerprints and suggested methods for recording them

• Acknowledged that no two prints are alike and do not change throughout a lifetime

• Three pattern types– Loops, Arches, and Whorls

Fundamental Principles of Fundamental Principles of FingerprintsFingerprints

• First Principle– A fingerprint is an individual characteristic.

No two fingers have yet been found to possess identical ridge characteristics

– Individuality of a fingerprint is not determined by its general shape or pattern but by careful study of ridge characteristics or minutiae

• Examples: bifurcation, enclosures, islands, ridge endings, short ridges, ridge crossings, deltas

Figure 14-1

Figure 14-2

• Second Principle– Fingerprints have been designed by nature to

increase grasp and to resist slippage and are formed in the fetal stage of development.

– Fingerprints are formed by:•Hills (Ridges): raised portions of the

epidermis•Valleys (Grooves): lowered portions of

the epidermis•IT IS THE RIDGES THAT ARE INKED

WHEN FINGERPRINTS ARE TAKEN

How are Fingerprints How are Fingerprints Formed?Formed?

• The Dermal Papillae is the boundary between the epidermis (outer skin) and the dermis (inner skin).

• The shape of this boundary is wavy. This wave pattern determines the pattern of the fingerprint and remains unchanged throughout your lifetime.

Leaving Your MarkLeaving Your Mark• Skin ridges have a single row of

pores that open from the sweat glands.

• Perspiration is discharged through the pores and oils from the body collect in the ridges and valleys.

• Impressions from the fingertips are transferred onto a surface, leaving a fingerprint.– Latent fingerprints are deposited in this

manner and cannot be seen with the naked eye.

• Third Principle

– Fingerprints have general ridge patterns that permit them to systematically classified.

Taking FingerprintsTaking Fingerprints• Fingers are rolled in ink left-to-

right, careful not to adhere too much ink to the fingertips

• The fingertips are then rolled left-to-right on a Ten-Print Card in the appropriate place for each finger

• A straight down print is then taken for each of the four fingers simultaneously and for each thumb and recorded on the Ten-Print Card

This is the original

Ten-Print Card of

Rosa Parks after the

Montgomery Bus

Boycott

ThreeThree Classes of Fingerprints Classes of Fingerprints

• Loops, Whorls, and Arches

– Loops: 65% of world’s population– Whorls: 30-35% of world’s population– Arches: 5% of world’s population

LoopLoop Patterns Patterns

• One or more ridges entering from one side of the print, recurving, and exiting from the same side

Types of Loop PatternsTypes of Loop Patterns• Ulnar Loop: loop opens toward

little finger• Radial Loop: loop opens toward

the thumb– Type Lines: pattern area of the loop

surrounded by two diverging ridges– Delta: the point directly in front of the

diverging ridges—loops MUST have at least one delta

– Core: the center of pattern

Types of Types of WhorlWhorl Patterns Patterns

• Four types of patterns– Plain Whorl– Central Pocket Loop Whorl– Double Loop Whorl– Accidental Whorl

All whorl patterns must have type lines and a MINIMUM of two deltas.

Types of Whorl PatternsTypes of Whorl Patterns

• Plain and Central Pocket Loops

– Plain whorl and central pocket loops have AT LEAST one ridge that makes a complete circuit

– Ridge may be a spiral, oval, or any variant of a circle

• Plain Whorl: an imaginary line is drawn between TWO deltas and the spiral is crossed

• Central Pocket Loop: spiral is not crossed when imaginary line is drawn

• Double Loop: has two loops in one fingerprint

• Accidental Loop: has two or more patterns or is not classified into any other category

Figure 14-6

ArchArch Patterns Patterns

• Plain arch: ridges entering one side of the fingerprint and exiting the other side

• Tented arch: this pattern rises sharply in the center

Arch PatternsArch Patterns

Figure 14-7

Classification of FingerprintsClassification of Fingerprints

• Original System: Henry System– Developed by Scotland Yard in 1901– Converted ridge patterns on all 10

fingers into a series of letters and numbers arranged into a fraction

– Problem: could only classify fingerprints up to 100,000 files

– Evolved into the FBI System of Fingerprint Classification

FBI SystemFBI System

• Primary System of Classification based on the Henry System

• All fingerprints in the world can be classified into 1,024 groups

How the How the FBI System FBI System WorksWorks

• Fingers are given numbers based on whorl patterns being present on each finger

R. Index R. Ring L. Thumb L. Middle L. Little 1 R. Thumb R. Middle R. Little L. Index L. Ring 1

16 8 4 2 0 Whorl

Values

Zeros are assigned for loops and archesFraction gives individualized result for each person

++ ++ +

Problems with Problems with FBI FBI SystemSystem

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

• Only useful when all 10 prints are available

• Cumbersome and Time Consuming to look through cards

• Often only one or two prints found at a crime scene

AFISAFIS

• Automated Fingerprint Identification System

• Computer-scans and digitally encodes fingerprints based on minutiae of ridge endings and bifurications

• List of prints is generated then a fingerprint examiner confirms match

Benefits of Benefits of AFISAFIS

• Computer can make thousands of accurate fingerprint comparisons in a second

• Can filter out imperfections in latent prints found at a crime scene

• Suspect lists are generated faster and investigators can spend more time focusing on suspects

A Typical AFIS Matching Screen

Types of Crime Scene Types of Crime Scene PrintsPrints

• Three Types:– Visible Prints– Plastic Prints– Latent (Invisible) Prints

Visible PrintsVisible Prints

• Can be seen with the naked eye

• Made by fingers touching a surface after ridges have been in contact with a colored material such as blood, paint, grease, ink, etc.

PlasticPlastic Prints Prints

• Can be seen with the naked eye• Made by ridge impressions left on

a soft material such as putty, wax, soap, dust, wet paint surfaces, etc.

LatentLatent Prints Prints

• Cannot be seen with the naked eye• Made by impressions caused by

transfer of body perspiration or oils present on finger ridges to the surface of an object

Detection of PrintsDetection of Prints

• Latent prints must be developed (found) through different methods

• The method used is dependent on the surface being examined

Surface ConditionsSurface Conditions

• Hard, nonabsorbent surfaces (glass, mirrors, tile, painted wood): Powders or SuperGlue Fuming

• Absorbent surfaces (paper, cardboard, cloth): One or more specific chemicals

Fingerprint PowdersFingerprint Powders• Non-absorbent surfaces only• Applied with a camel’s hair or

fiberglass brush• Color of powder chosen contrasts with

surface color• Powder adheres to oils and

perspiration left by ridges• Print can be lifted off the surface and

preserved

Iodine FumingIodine Fuming• Oldest chemical method for developing

latent prints• Iodine is a solid crystal that, when

heated, is transformed into a gas through sublimation

• Material is placed in a chamber and iodine is heated and latent prints are revealed

• Iodine prints are not permanent and must be photographed immediately or fixed with starch solution, which can last about 1 month

NinhydrinNinhydrin

• Chemical used to develop prints on porous material by reacting with amino acids in perspiration

• Developed prints appear purple-blue in color

• Prints appear within an hour or two and fully developed in 24-48 hours

• Commonly used on paper products

Latent Prints recovered on paper with Ninhydrin

Physical DeveloperPhysical Developer• Silver-nitrate based chemical• Useful for detecting prints that

cannot be found by other methods or on objects that have been wet at one time

• Application of Physical Developer washes away any protein that may be present and MUST be used last

SuperGlueSuperGlue Fuming Fuming• Used on nonporous surfaces such as

metal, electrical tape, leather, and plastic bags

• Active ingredient: cyanoacrylate ester• Evidence is placed in a fuming

chamber and the cyanoacrylate is heated and covers the object and produces a white latent print

Flashlight battery exposed to SuperGlue Fuming

Laser LightLaser Light

• Perspiration contains a variety of components that fluoresce when illuminated by laser light

• Because of the fluorescence, latent prints can be seen with the naked eye

• Almost never used anymore with the invention of alternate light source latent print examination

Alternate Light SourceAlternate Light Source• Works because perspiration

fluoresces under different wavelengths of light

• Can adjust the wavelength of light to be aimed through a fiber optic cable

• More commercially available than laser light setups

Alternative Light Source being used to detect latent prints

Preservation of PrintsPreservation of Prints

• Common fingerprint methods do not interfere with further DNA analysis

• However, when biological material remains, fingerprints should be developed at the crime lab instead of at a crime scene

• After prints have been found, photos must be taken

• If object is small enough to be transported without destroying the print, it should be preserved intact

• Cellophane should cover the print to protect from damage

• Prints on immovable objects should be lifted

• Lifted prints should be preserved on a card that provides contrast

Fingerprints Chapter 14 Criminalistics. History of Fingerprinting –First systematic attempt at...

Documents