Fingerprints. Chapter 4 Fingerprints 2 Kendall/Hunt Publishing Company 2 Fundamental Principles of Fingerprints A fingerprint is an individual characteristic

Fingerprints

Chapter 4

FingerprintsFingerprints

2Kendall/Hunt Publishing Company

2

Fundamental Principles of Fingerprints

A fingerprint is an individual characteristic.

A fingerprint remains unchanged during an individual’s lifetime.

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

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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.

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There are 3 main fingerprint patterns found in the human population:

Loops: found in 60% of the population Whorls: found in 30% of the population Arches: found in 10% of the population A typical loop must have one or more ridges

that enter from one side, loop, and then exit from the same side.


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October 4, 2011: Activity – page 77 # 1

Look at your fingerprints under the magnifying glass. Draw each of your prints in the boxes on the worksheet. Figure out whether they have arches, whirls, or loops.


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Fingerprint Analysis – page 77 - # 2 Inkprint all of your fingerprints Students work in groups of four: Compare your

fingerprints to the other people in your group 1. What were some similarities in your group? 2. What were some differences in your group? 3. What are some problems you can foresee when using

fingerprints to identify people? 4. What are some questions you have that you want

answered by the end of this unit?


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AFIS

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

Established in the 1970s

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

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Fingerprint Minutiae

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LOOP WHORL ARCH

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Arch

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

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Loop A loop must have one or more ridges entering and exiting from the same side. Loops must have one delta. A double loop is made of two loops.

Types

Radial—opens toward the thumb

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

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Whorl

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

TypesPlainCentral pocketDouble loopAccidental

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Primary Classification

The Henry-FBI Classification System

Each finger is given a point value.

right left

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Primary Classification, continued

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 total number is your primary classification number.

=

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Comparison

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.

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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.

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Developing Latent Prints

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.

Ninhydrin—reacts with amino acids to produce a

purple color.

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Iodine Fingerprint

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Other Prints

Lips—several common patterns

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

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Other Prints, continued

Palm—friction ridges can be

identified and may be used

against suspects

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Footprints are taken at birth

as a means of identification of

infants.

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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.

Earprint catches murderer

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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.

Documents

Fingerprints. Chapter 4 Fingerprints 2 Kendall/Hunt Publishing Company 2 Fundamental Principles of Fingerprints A fingerprint is an individual characteristic