Fingerprints

Chapter 4

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Do Now (5 mins)• Fingerprints are found at a

crime scene. • What type(s) of evidence

are fingerprints? Why?

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Fingerprintsa)Physical evidenceb)Trace evidence

Why trace?

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Fingerprint Principles (3)

According to criminal investigators, fingerprints follow 3 fundamental principles:

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

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2. 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.

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

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Ridges – unique patterns of lines in fingerprints

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• Video #1, Video #2

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On Your Own…• After watching the two videos, explain the

following statement:

• “Immigrants in Lawrence, MA have frequently and unsuccessfully attempted to alter their fingerprints.”

a) Why would it be so common?b) Why is it so often unsuccessful?

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Do Now (5 mins)

• Can your fingerprints be duplicated?

• Can your fingerprints be removed?

• Explain why/why not.

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8th Grade Forensic Science

A Closer Look at Fingerprints

Image from ftp://sequoyah.nist.gov/pub/nist_internal_reports/ir_6534.pdf T. Trimpe 2007 http://sciencespot.net/

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

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Fingerprints:• made of a series of ridges and

valleys on the surface of the finger. • Are unique because of..a) pattern of ridges and valleysb) minutiae points, which are points

where the ridge structure changes.

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minutiae• are major features of a

fingerprint

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Automated Fingerprint Identification System (AFIS)

http://www.fdle.state.fl.us/CrimeLab/images/fingerrint%20comparison%20for%20afis.jpg

a computerized system capable of reading, classifying, matching, and storing fingerprints for criminal justice agencies.

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ComparisonComparison There are no legal requirements

in the United States on the number of points. Generally, criminal courts will accept 8 to 12 points of similarity.

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1 – Blow up your balloon about halfway and twist the end to keep the air from coming out. Do not tie it off!

2 – Use an ink pad to make a print with all of your fingers and label each one with a permanent marker. Write your name on the balloon as well.

3 – Blow up the balloon to full size and tie the end.

4 – Analyze the fingerprints to find several ridge structures that we have discussed. Use a highlighter to mark these structures on your “My Prints” worksheet.

Try It!

Think About It!

Which ridge structures were most common in your fingerprints?

Which ridge structures were most common in your group?

Were there any structures that were not found in any of the fingerprints?

Balloon Fingerprint Activity: http://www.msichicago.org/fileadmin/Education/learninglabs/lab_downloads/fingerprint_analysis.pdf

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Balloon Prints

• After putting your print on a balloon, blow up the balloon.

• Describe 3 structures in your fingerprint that stand out.

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Do Now (5 mins)

• How is a ridge different from a valley?

• Name THREE things that make your fingerprint unique

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Rid

ge C

har

acte

rist

ics

Use these characteristics as points of identification when comparing fingerprint samples. The more points you can find in common, the better the match!

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Ridge Characteristics

Crossover

Core

Bifurcation (fork)Ridge ending

Island

Delta

Pore

Scar

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•Two bifurcations•One trifurcation•One eye•One island (dot)•TWO deltas

Chapter 4http://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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Do Now (5 mins)

• Describe the difference between a delta and a bifurcation.

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Do Now (5 mins)

• Without looking back at notes, draw the following:

- Bifurcation- Trifurcation- Island (Dot)- Eye

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Fingerprint ClassesThere are 3 specific classes for all fingerprints based upon their visual pattern: arches, loops, and whorls.

Each group is divided into smaller groups as seen in the lists below.

ArchPlain arch

Tented arch

LoopRadial Loop

Ulnar loop

WhorlPlain whorl

Central pocketDouble loopAccidentical

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LoopLoop

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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Loops- one delta

- one or more ridges that enter and leave on the same side. for their positions related to the radius and ulna bones.

Delta

Ulnar Loop (Right Thumb)

Loop opens toward right or the ulna bone.

Radial Loop (Right Thumb)

Loop opens toward the left or the radial bone.

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Whorls-form a complete circuit

- have at least two deltas.

Plain Whorl

Central Pocket Whorl

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Whorls – Part 2

Accidental Whorl

Accidental whorls contain two or more patterns (not including the plain arch), or does not clearly fall under any of the other categories.

Double Loop Whorl

Double loop whorls are made up of any two loops combined into one print.

Delta

Delta

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Arches-simplest type of fingerprints that are formed by ridges

- No deltas are present.

Plain Arch Tented Arches

Spike or “tent”

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ArchArch An arch has ridges that enter on one side of the finger and cross to the other side while rising upward in the middle.

- NO DELTAS!

Types:PlainTented

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Arch Loop Whorl

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Fingerprint Factoid

- 60% of people have loops- 35% have whorls - 5% have arches

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Fill in the following table…Arch Loop Whorl

Draw how it looks.# of deltas presentDifferent types of itHow common?

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Identify each fingerprint pattern.

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Right Hand

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Do Now (5 mins)

• Next slide

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It’s time to makesome prints!

Avoid Partial Prints

GOOD PRINTGet as much of the top part of your finger as possible!

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Directions

1st – Roll the “pad” portion of your thumb over the ink pad from the left side of your thumb to the right. You do not have to push down really hard!

2nd – Roll the “pad” portion of your thumb from the left side of your thumb to the right in the correct box on your paper to make a thumbprint.

3rd – Continue this process to make a fingerprint of all ten fingers on the “My Prints” worksheet.

4th –Use your notes and a magnifying lens to help you figure out what type of pattern is found in each of your fingerprints. Label each one with the pattern’s name.

Do Now (5 mins)

Why do we leave fingerprints?

Example) smudges on your cell phone

Answer:

Because our hands naturally produces oils

These are called secretions

Why Do We Have Fingerprints?

Most secretions come from three

glands:

1. Eccrine—largely water with both inorganic and organic compounds

Most important for fingerprints.

2. Apocrine—secrete pheromones and other organic materials.

Most secretions come from three glands:

Most secretions come from three

glands:

3. Sebaceous—secrete fatty or greasy substances.

The THREE types of fingerprints are…

1. Loop 2. Arch 3. Whorl

Types of fingerprints Whorl, loop, and arch represent

types of fingerprint patterns

TYPES of fingerprints demonstrates how prints are left behind

Types of fingerprints

1. Exemplar prints 2. Latent prints 3. Patent prints 4. Plastic prints

With a partner…

Using a BLUE Forensic Science book, define the 4 types of fingerprints

Exemplar prints

-fingerprints deliberately collected from a subject-for purposes of enrollment in a system or when under arrest for a suspected criminal offense-Happens during an arrest or during an FBI background check

Exemplar Print

Latent prints

- hidden or invisible- usually left accidentally-less clarity and content

Latent prints

Patent prints- friction ridge impressions which are observable -obvious examples would be impressions from flour and dirt- are photographed- can be left on a surface by materials such as ink, dirt, or blood.

Patent prints

Plastic prints-friction ridge impression left in a material that retains the shape of the ridge detail.

-Example: criminal leaves his print in a piece of clay

-Frequently seen in things like moulding and window frames

Plastic prints

Do Now ( 5 mins)

What kind of fingerprint is a fingerprint left in bubble gum? WHY?

What kind of fingerprint is left if you touch a table with clean hands? WHY?

What kind of fingerprint is left if your hands are covered in dirt? WHY?

A good fingerprint…

-square-no smudging-visible ridges

Practice the process…

1. Have partner touch your thumb to the ink pad

2. Have partner place your thumb on it’s SIDE (on the nail) on the index card

3. Have partner roll your thumb “nail to nail”

4. If it’s your RIGHT hand…roll thumb LEFT to RIGHT

5. If it’s your LEFT hand…roll thumb RIGHT to LEFT

Practice the process…

Try each side of the index card a few times

Before moving on, Mr. Smith must verify that your fingerprint is good enough

On Your Own…

Get a “Fingerprint Identification Card” and take a print of each finger on your hand

Each print should have visible ridges, and should be rolled in the appropriate direction

This is due at the end of class!

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Type 1:Latent PrintsType 1:Latent Prints

not visible to the naked eye.

secretions of human skin and require development for them to become visible.


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Developing Latent Developing Latent PrintsPrints

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.


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Developing Latent Developing Latent PrintsPrints

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.


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Iodine FingerprintIodine Fingerprint


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Ninhydrin FingerprintNinhydrin Fingerprint


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Cyanoacrylate Cyanoacrylate FingerprintsFingerprints


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Other PrintsOther 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.


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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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Lips—display several common patterns

Short vertical lines Short horizontal lines Crosshatching Branching grooves


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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.


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


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AFISAFIS

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


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BiometricsBiometrics

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.


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More about PrintsMore about Prints

For additional information about prints and crime, check out Court TV’s Crime Library

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


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Documents

Fingerprints