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Fingerprints. Lesson 1 – Fingerprints at the Crime Scene. Lesson Essential Questions: How are fingerprints used as evidence in crime scenes?. According to criminal investigators, fingerprints follow 3 fundamental principles:

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lesson 1 fingerprints at the crime scene
Lesson 1 – Fingerprints at the Crime Scene

Lesson Essential Questions:

  • How are fingerprints used as evidence in crime scenes?

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According to criminal investigators, fingerprints follow 3 fundamental principles:

A fingerprint is an individual characteristic; no two people have been found with the exact same fingerprint pattern.

A fingerprint pattern will remain unchanged for the life of an individual; however, the print itself may change due to permanent scars and skin diseases.

Fingerprints have general characteristic ridge patterns that allow them to be systematically identified.

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

Juan Vucetich—developed a fingerprint classification system based on Galton’s that is used in Spanish-speaking countries

DactyloscopyThe Study of Fingerprints

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Friction ridges (ridges and valleys) are present on the outer layer of our skin that make up our fingerprint. – Not due to genetics.

  • Outer epidermal layer separated from an inner dermal layer separated by papillae
    • The papillae form a boundary that determines the friction ridge.

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fundamental principles of fingerprints
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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Using Fingerprints at a Crime Scene Video

Fingerprints inside the Lab

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Lesson 2 – Classifying Fingerprints

    • Essential Questions:
      • How are fingerprints classified?
      • What are the basic differences in fingerprints?

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All fingerprints can be classified into 3 basic patterns:

    • Loops
    • Whorls
    • Arches

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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.

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?

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whorl
Whorl

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.

Types

Plain

Central pocket

Double loop

Accidental

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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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primary classification
Primary Classification

The Henry-FBI Classification System

Each finger is given a point value. If your finger has a whorl pattern it is given a number.

right

left

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primary classification continued
Using your fingerprint sheet, assign the number of points for each finger that has a whorl and substitute into the equation:Primary Classification, continued

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.

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Switch cards with others in the class and determine their types of fingerprints and classification numbers.

  • Fingerprint Factoid:
    • 60% of people have loops, 35% have whorls,
    • and 5% have arches

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Ridge Classification

    • You have classified fingerprints according to general patterns.
    • Ridge Classification uses individual ridge characteristics or minutiae.

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The uniqueness of a fingerprint can be determined by the pattern of ridges and valleys as well as the minutiae points, which are points where the ridge structure changes.

Did you know?

The koala is one of the few mammals (other than primates) that has fingerprints. In fact, koala fingerprints are remarkably similar to human fingerprints; even with an electron microscope, it can be quite difficult to distinguish between the two.

  • Ridgeology: The study of the uniqueness of friction ridge structures and their use for personal identification.1

1Introduction to Basic Ridgeology by David Ashbaugh, May 1999 Image from http://www.cs.usyd.edu.au/~irena/minutia.gif

ridge characteristics
Ridge Characteristics

Minutiae—characteristics of ridge patterns

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fingerprint minutiae
Fingerprint Minutiae

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comparison
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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http://www.dkfz.de/tbi/projects/bmcv/images/iu_it246_04s_fingerprint1.jpghttp://www.dkfz.de/tbi/projects/bmcv/images/iu_it246_04s_fingerprint1.jpg

How many ridge characteristics can you identify in this fingerprint?

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Lesson 3 – Fingerprinting Techniques:

    • 1. What techniques are used to compare fingerprints?

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Did you know? Camel hair is the most common animal hair used to make fingerprint brushes. Now many brushes (like the one above) are made out of fiberglass.

  • Latent prints are impressions left by friction ridge skin on a surface, such as a tool handle, glass, door, etc.
  • Prints may be collected by revealing them with a dusting of black powder and then lifted with a piece of clear tape.
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Magnetic powder can also be used to reveal latent prints. This type of powder works better on shiny surfaces or plastic baggies or containers.

Some investigators use fluorescent powder and UV lights to help them find latent prints on multi-colored or dark surfaces.

The cyanoacrylate fuming method (often called the super glue method) is a procedure that is used to develop latent fingerprints on a variety of objects.

Ninhydrin is a chemical that bonds with the amino acids in fingerprints and will produce a blue or purple color. It is used to lift prints from surfaces such as paper and cardboard.

In modern labs, lasers can be used.

Bottom Left: http://www.ok.gov/osbi/images/ninhydrin%20print.jpg

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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

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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.

Biometrics

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iodine fingerprint
Iodine Fingerprint

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ninhydrin fingerprint
Ninhydrin Fingerprint

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cyanoacrylate fingerprints
Cyanoacrylate Fingerprints

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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

Other Prints

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other prints continued
Other Prints, continued

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

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other prints continued1
Other Prints, continued

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

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other prints continued2
Other Prints, continued

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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other prints continued3
Other Prints, continued

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.

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other prints continued4
Other Prints, continued

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

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more about prints
For additional information about prints and crime, check out truTV’s Crime Library:

www.crimelibrary.com/criminal_mind/forensics/fingerprints/1.html

More about Prints

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