Forensic Science: Fundamentals & Investigations, Chapter 6 1 C6: Fingerprint Analysis

Forensic Science: Fundamentals & Investigations, Chapter 6 1

C6: Fingerprint Analysis


Chapter 6 Fingerprints By the end of this chapter you will be able to:

discuss the history of fingerprinting describe the characteristics of fingerprints and

fingerprinting minutiae explain when and how fingerprints are formed describe what causes fingerprints to be left on objects identify the basic types of fingerprints describe how criminals attempt to alter their fingerprints

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Chapter 6 Fingerprints By the end of this chapter you will be able to:

determine the reliability of fingerprints as a means of identification

describe the Integrated Automated Fingerprint Identification System (IAFIS)

explain how fingerprint evidence is collected describe the latest identification technologies determine if a fingerprint matches a fingerprint on

record use the process of lifting a latent print


Historical DevelopmentHistorical Development

1. The oldest known documents showing fingerprints date from third century B.C. China.

2. In ancient Babylon (dating back to 1792-1750 B.C.), fingerprints pressed into clay tablets marked contracts.

3. The earliest written study (1684) is Dr. Nehemiah’s paper describing the patterns he saw on human hands under a microscope, including the presence of ridges.

4. In 1788, Johann Mayer noted that the arrangement of skin ridges is never duplicated in two persons. He was probably the first scientist to recognize this fact.


Historical Development Historical Development

5. Nine fingerprint patterns were described in 1823 by Jan Evangelist Purkyn.

6. Sir William Herschel (shown at the right), in 1856, began the collection of fingerprints and noted they were not altered by age.

7. Alphonse Bertillon created a way to identify criminal’s prints that was used in 1883 to identify a repeat offender.

8. In 1888, Sir Francis Galton (shown at the right), and Sir Edmund Richard Henry, developed the fingerprint classification system that is still in use in the United States.


Historical Development Historical Development

9. In 1891, Iván (Juan) Vucetich improved fingerprint collection. He began to note measurements on identification cards, as well as adding all ten fingerprint impressions. He also invented a better way of collecting the impressions.

10. Beginning in 1896, Sir Henry (mentioned in the last entry on the previous slide), with the help of two colleagues, created a system that divided fingerprints into groups. Along with notations about individual characteristics, all ten fingerprints were imprinted on a card (called a ten card).


Old Method of Identification (pre-1990)

Could take up to three months to find a match

What was he looking at?


A ten card


IAFISAutomated fingerprint identification service links police forces internationally

Results within two hours


The Automated Fingerprint Identification System—a computer system for storing and retrieving fingerprints

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

By the 1990s, most large jurisdictions had their own system in place. The problem: A person’s fingerprints may be in one AFIS database but not in others.

IAFIS—the FBI’s Integrated Automated Fingerprint Identification System, which is a national database of all 10-print cards from all over the country

AFIS


Fingerprints are possiblebecause:

Fingers have unique ridge patterns

Fingers produce secretionsThese secretions stick to surfaces


Did You Know?

Your fingerprints are hereditaryThey are totally uniqueThey will never change They form in the dermal papillae

and will always return even after scarring or burning


Did You Know?

Gloves do not necessarily keep you from leaving fingerprints

You can leave prints through surgical gloves

They can be turned inside out to produce a print also

Leather works this way too


Secretions from fingers include:

OilsSaltWaterProteins


What Are Fingerprints?

All fingers, toes, feet, and palms are covered in small ridges.

These ridges are arranged in connected units called dermal, or friction, ridges.

These ridges help us get or keep our grip on objects.

Natural secretions plus dirt on these surfaces leave behind an impression (a print) on those objects with which we come in contact.


Your skin:


Formation of Fingerprints

An animal’s external tissue (skin) consists of (a) an inner dermis and (b) an outer epidermis.

The creation of fingerprints occurs in a special layer (the basal layer) in the epidermis where new skin cells are produced.

Fingerprints probably begin forming at the start of the 10th week of pregnancy.

Because the basal layer grows faster than the others, it collapses, forming intricate shapes.


Fingerprints are:

Visible on surfaces such as a drinking glass, mirror or other smooth, reflective surface

OrInvisible (called Latent) and have

to be treated to be visible


Fingerprint surfaces

Practically any surface including:WoodCardboardObjects in waterSkin (neck, bruises elsewhere)


Fingerprint Patterns

Eight basic patterns recognized by the FBI

Ten basic details within the patterns

At least 12 identical points are necessary for a match


Characteristics of Fingerprints

There are 3 general fingerprint distinctions:

ARCH WHORL LOOP

About 5% About 30% About 65% of the population


Fingerprints include:

Loops

Whorls

Arches



Basic patterns can be further divided: – Arch patterns can be plain (4%) or tented

(1%). – Whorl patterns can be central pocket (2%),

double loop (4%), or accidental (0.01%). Even twins have unique fingerprints due to

small differences (called minutiae) in the ridge patterns.


An arch has friction ridges that enter on one side of the finger and cross to the other side while rising upward in the middle. They do NOT have type lines, deltas, or cores.

Types

Plain

Tented

Characteristics of an Arch


Tented Arch Plain Arch


A loop must have one or more ridges entering and exiting from the same side. Loops must have one delta.

Types

Radial—opens toward the thumb

Ulnar—opens toward the “pinky” (little finger)

Which type of loop is this, if it is on the right hand? Left hand?

Characteristics of a Loop


Examples of Loop Patterns


A plain or central pocket whorl has at least one ridge that makes a complete circuit. A double loop is made of two loops. An accidental is a pattern not covered by other categories. Whorls have at least two deltas and a core.

TypesPlain

Central pocket

Double loop

Accidental

Characterics of Whorls


Examples of Whorl Patterns


Notice the scar



Forensic examiners look for the presence of a core (the center of a whorl or loop) and deltas (triangular regions near a loop).

A ridge count is another characteristic that distinguishes one fingerprint from another. The count is made from the center of the core to the edge of the delta.


Ridge patterns


Ridge Patterns


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.

Comparison of Fingerprints


Types of Fingerprints

There are 3 types of prints that investigators look for at crime scenes:

1. Patent fingerprints are visible prints transferred onto smooth surfaces by blood or other liquids.

2. Plastic fingerprints are indentations left in soft materials such as clay or wax.

3. Latent fingerprints are not visible but made so by dusting with powders or the use of chemicals.


Latent Fingerprints

Can be treated with various powders to help see the ridge patterns better.

These powders include:

manganese dioxide

graphite

a trace of metals in them (like aluminum).


Powders

Gray for dark objectsBlack for light colored objectsChalk dust can be used if viewed on a

dark background

Prints can be ‘lifted’ off a surface using adhesive tape


Latent prints can bevisualized using

‘Superglue’ in a sealed chamberUsing iodine vapor in a sealed

chamber


Fingerprint Forensic FAQs

How are latent fingerprints collected?


Developing a print requires substances that interact with secretions, causing the print to stand out against its background. It may be necessary to attempt more than one technique, done in a particular order so as not to destroy the print.

Powders—adhere to both water and fatty deposits. Choose a color

to contrast with the background.

Iodine—fumes react with oils and fats to produce a

temporary yellow-brown color.

Developing Latent Fingerprints


Ninhydrin—reacts with amino acids to produce a purple color.

Silver nitrate—reacts with chloride to form silver chloride, a material that turns gray when exposed to light.

Cyanoacrylate—“superglue” fumes react with water and other fingerprint constituents to form a hard, whitish deposit..

In modern labs and criminal investigations, lasers and alternative light sources are used to view latent fingerprints. These were first used by the FBI in 1978. Since lasers can damage the retina of the eye, special precautions must be taken.

Developing Latent Prints, cont’d


Fingerprint Forensic FAQs

Can fingerprints be erased? No, if, for example, they are removed with chemicals, they will grow back.

Is fingerprint identification reliable? Yes, but analysts can make mistakes.

Is fingerprint matching carried out by computers in a matter of seconds? No, but the FBI’s Integrated Automated Fingerprint Identification System (IAFIS or AFIS) can provide a match in up to 2 hours for the prints in its Master File.


A famous set of prints

JohnDillinger


Other Prints: Ear Print

A man has been convicted of suffocating an eldery woman on the basis of earprint evidence. The assailant was caught after police matched the inprint 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.


The Future of Fingerprinting New scanning technologies and digitally

identifying patterns may eliminate analytical mistakes.

Trace elements of objects that have been touched are being studied to help with the identification of individuals.

To help with identification, other physical features such as eyes and facial patterns are also being studied.


. . . . . . . . . . . . . . . . . Summary. . . . . . . . . . . . . . . . . Summary

Fingerprints have long been used for identification, and in the mid-1800s were recognized as unique to each person.

Three main groups include arches, whorls, and loops. Basic analysis includes looking for cores, deltas, and

making a ridge count. Investigators search for patent, plastic, and latent prints. Dusting with powders or using special chemicals can make

latent fingerprints visible. New developments may eliminate errors by analysts.

Documents

Forensic Science: Fundamentals & Investigations, Chapter 6 1 C6: Fingerprint Analysis