Fingerprints

Chapter 4

Notes

Mrs. Morgan

A Quick Preview

Recording and classifying prints

• Rolling inked prints

• Loops, whorls, arches, minutiae

• Primary identification number

Lifting prints

• Black, white, and fluorescent powder

• Chemicals—ninhydrin, iodine, silver nitrate, cyanoacrylate

Other types of prints

• Palm, lip, teeth, eye, ear, voice, shoeprints, and footprints

A Brief History…Dactyloscopy

The Study of Fingerprints

History from 1850 to 1900

William Herschel—required Indians to put their fingerprints on contracts, and used fingerprints as a means of identifying prisoners

Henry Faulds—claimed that fingerprints did not change over time and that they could be classified for identification

Alphonse Bertillon—proposed body measurements as a means of identification; termed anthropometry

Francis Galton—developed a primary classification scheme based on loops, arches, and whorls

Edward Richard Henry—in collaboration with Galton, instituted a numerical classification system

The Fundamental Principles

Fingerprint are individual

characteristics.

A fingerprint remains unchanged

during an individual’s lifetime.

Formed during fetal development –

genetic & movement formed

Fingerprints have characteristic ridge

patterns that permit them to be

systematically classified.

Ridge Characteristics

Minutiae

Characteristics

ofridge patterns

Fingerprint Minutiae

Fingerprint Patterns

All friction ridges are divided into 3 classes by their general pattern

Loops 60 %

Whorls 35 %

Arches 5 %

Loopsone or more ridges which enter from one side of the print and exit on the same side

• Area surrounding the loop are 2

diverging ridges called type lines

• Delta: a ridge point nearest the

type line divergence.

• All loops must have at least 1

delta.

Ulnar Loops

opens towards the little finger

Ridges enter and exit from the same side

Delta and type lines

Radial Loops

opens toward the

thumb

Ridges enter and exit from the same side

Delta and type lines

Whorls

• Must have 2 type lines and 2 deltas

• Divided into 4 groups

• Plain whorl

• Central pocket whorl

• Double loop whorl

• Accidental whorl

Plain Whorlmust have at least 1 ridge that makes a

complete circuit around the fingerprint

Deltas and type lines

At least 1 ridge which goes all the way

around

Central Pocket Whorls

At least 1 ridge that goes all the

way around inside of a loop

Deltas and type lines

Whorl

Loop

Double Loop Whorl2 loops within the same point (2 deltas so it is considered a whorl)

Deltas and type lines

Loops

Accidental Whorlsany combination of patterns not

covered by the other groups

Deltas and type lines

whorlloop

Plain Archridges enter 1 side and exit from

the opposite side

Ridges enter and exit from opposite sides

No deltas

Tented Archsharp peak at the center

of the arch

Ridges enter and exit from opposite sides

Sharp peak at center

Fingerprint Classification

Primary Classification

The Henry-FBI Classification System

Each finger is given a point value.

Primary Classification

Assign the number of points for each finger that

has a whorl and substitute into the equation:

right right left left left index ring thumb middle little + 1

right right right left left thumb middle little index ring + 1

That number is your primary classification number.

=

Comparing Fingerprints• Minutiae are identified in the print

and compared to minutiae in

other, known prints.

• There are no legal requirements

in the United States on the

number of points required for a

match. Generally, criminal courts

will accept 8 to 12 points of

similarity.

• The more points that match, the

more confident an analyst can

be.

Kickin’ it Old School

• Fingerprint analysts would manually compare an evidence print to known prints

• Known prints would be cataloged by classification in large books

IAFIS

Established in the 1970s, AFIS

enables law enforcement

officials to:

• Search large files for a set of

prints taken from an individual

• Compare a single print, usually a

latent print developed from a

crime scene

Integrated Automated Fingerprint Identification System

Processing and Recovering

Prints

• Prints should be the 1st physical evidence recovered from a crime scene

• All prints must be photographed before they are disturbed or moved

• Processing of prints depends on the nature of the print

• 3 types of prints exist

Plastic: 3-D impression into a substance such as wax, soap, putty or dust

3 Types of Prints

Visible: left by fingers coated with a colored substance like blood, grease, paint, dirt and ink

Latent: lie hidden or are relatively invisible. Need processing or developing to see

Composition

Prints made of perspiration composed of moisture, sodium

chloride (salt), amino acids, organic/inorganic substances,

and dead skin cell

• How a print is developed depends on the material or surface the print is left in.

• Easily destroyed – do not touch or smear

• Always wear gloves

Tools

• Flashlight

• Magnifying glass

• Alternate light source (UV, colored filter)

• Laser detection system

• Powders

• Brushes

• Tape

• Additional materials

Developing Latent Prints

• Need a substance that interacts with secretions, causing the print to stand out against its background.

• May need to use multiple techniques, done in a particular order so as not to destroy the print.

Most commonPowders—adhere to moisture and

come in many colors and type

Iodine

fumes react with oils and fats to produce a

temporary yellow-brown color.

Developing Latent Prints

Ninhydrin

reacts with amino acids to

produce a purple color.

Developing Latent Prints

Cyanoacrylate

“superglue” fumes react with

water and other fingerprint

constituents to form a hard,

whitish deposit.

Developing Latent Prints

Silver nitrate

reacts with chloride to form silver

chloride, a material that turns gray

when exposed to light.

Developing Latent Prints

More than fingers

Voice

electronic pulses

measured on a

spectrograph

Foot

size of foot and

toes; friction ridges

on the foot

Shoes

can be compared and identified

by type of shoe, brand, size, year

of purchase, and wear pattern

Lips

several common

patterns

Weird Prints

A man has been convicted of suffocating an elderly woman on

the basis of earprint evidence. The assailant was caught after police

matched the imprint of his ear on the victim’s window. Police believe

that the thief put his ear to the window to listen for signs of

anyone home.

Earprint catches murderer