Fingerprints By the end of this chapter you will be able to: discuss the history of fingerprinting



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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

  • determine the reliability of fingerprints as a means of identification

  • describe the Integrated Automated Fingerprint Identification System (IFAIS)

  • 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




Dactyloscopy -

Historical Development

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

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

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.

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.

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

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

Alphonse Bertillon created a way to identify criminals that was used in 1883 to identify a repeat offender.

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.

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.

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).

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.

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




Principles of Fingerprints

First Principle: A fingerprint is an individual characteristic; no two fingers have yet been found to posses identical ridge characteristics.

Second Principle: A fingerprint will remain unchanged during an individual's

lifetime.

John Dillinger - example)

Third Principle: Fingerprints have general ridge patterns that permit them to be

systematically classified.


Characteristics of Fingerprints

  • 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.

There are 3 general fingerprint distinctions:

ARCH WHORL LOOP

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

  • 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.

Ridgeology -

Fingerprint Minutiae- characteristics of ridge patterns

Primary Classification

Assign the number of points for each finger that has a whorl and substitute into

the equation:



Fingerprint Identification

AFIS

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

  • Began in the early 1970’s 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 1990’s most large jurisdictions had their own system in place. The problem - a person’s fingerprints may be in one AFIS 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

Types of Fingerprints

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

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

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

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

Latent Prints

  • Latent fingerprints are those that are not visible to the naked eye. These prints consist of the natural secretions of human skin and require development for them to become visible.




  • Most secretions come from three glands:

  • Eccrine—largely water with both inorganic (ammonia, chlorides, metal ions, phosphates) and organic compounds (amino acids, lactic acids, urea, sugars). Most important for fingerprints.

  • Apocrine—secrete pheromones and other organic materials.

  • Sebaceous—secrete fatty or greasy substances.

Developing Latent Prints

  • Developing a print requires substances that interact with secretions that cause 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 the background.

  • Iodine—fumes react with oils and fats to produce a temporary yellow brown reaction.

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

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

  • Cyanoacrylate—“super glue” 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.

Iodine Fingerprint

Ninhydrin Fingerprint

Cyanoacrylate Fingerprints




Fingerprint Forensic FAQs

  • How are latent fingerprints collected?

  • 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 2 hours for the prints in its Master File.




Other Prints

  • Ears—shape, length and width

  • 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.

Palm—friction ridges can be identified and may be used against suspects.

Footprints are taken at birth as a means of identification of infants.

Lips—display several common patterns

  • Short vertical lines

  • Short horizontal lines

  • Crosshatching

  • Branching grooves




Teeth—bite marks are unique and can be used to identify suspects. These imprints were placed in gum and could be matched to crime scene evidence.

The blood vessel patterns in the eye may be unique to individuals. They are used today for various security purposes.




Biometrics

  • Use of some type of body metrics for the purpose of identification. (The Bertillon system may actually have been the first biometry system.)

  • Used today in conjunction with AFIS

  • Examples include retinal or iris patterns, voice recognition, hand geometry

  • Other functions for biometrics—can be used to control entry or access to computers or other structures; can identify a person for security purposes; can help prevent identity theft or control social services fraud.




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

  • 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.



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