Fingerprints

T. Trimpe 2006 http://sciencespot.net

Fingerprint Principles

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.

Fingerprint Classes

There 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 LoopUlnar loop

WhorlPlain whorl

Central pocket whorlDouble loop whorl

Accidentical

Interesting Info

Did you know?Dactyloscopy is the study of fingerprint identification.

Police investigators are experts in collecting “dactylograms”, otherwise known as fingerprints.

Fingerprint Factoid: 60% of people have loops, 35% have whorls,

and 5% have arches

ArchesArches are the simplest type of fingerprints that are formed by ridges that enter on one side of the print and exit on the other. No deltas are present.

Plain ArchRidges enter on one side and

exit on the other side.

Tented Arches Similar to the plain arch,

but has a spike in the center.

Spike or “tent”

LoopsLoops must have one delta and one or more ridges that enter and leave on the same side. These patterns are named 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.

NOTE: On the left hand, a loop that opens to the left would be an ulnar loop, while one that opens to the right would be a radial loop.

WhorlsWhorls have at least one ridge that makes (or tends to make) a complete circuit. They also have at least two deltas. If a print has more than two deltas, it is most likely an accidental.

Draw a line between the two deltas in the plain and central pocket whorls. If some of the curved ridges touch the line, it is a plain whorl. If none of the center core touches the line, it is a central pocket whorl.

Plain Whorl

Central Pocket Whorl

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

Identify each fingerprint pattern.

Right Hand

Left Hand

Left Hand

Right Hand

Right Hand

Fingerprint Activity

Fingerprint Unit VocabularyArch- a fingerprint pattern in which the ridge pattern originates from one side of the print and leaves from the other side. Core- a center of a loop or whorl Delta- a triangular ridge pattern with ridges that go in different directions above and below a triangle Fingerprint- an impression left on any surface that consists of patterns made by the ridges on a finger. Latent Fingerprint- a hidden fingerprint made visible through the use of powders or other techniques. Loop- a fingerprint pattern in which the ridge pattern flows inward and returns in the direction of the origin. Minutiae- the combination of details in the shapes and positions of ridges in fingerprints that made each unique; also called ridge characteristics. Patent Fingerprint- a visible fingerprint that happens when fingers with blood, ink, or some other substance on them touch a surface and transfer the pattern of their fingerprint to that surface. Plastic Fingerprint- a three-dimensional (3-D) fingerprint made in soft material such as clay, soap, or putty. Ridge Pattern- the recognizable pattern of the ridges found in the end joints of fingers that form lines on the surfaces of objects in a fingerprint. They fall into three categories: arches, loops, and whorls. Ten Card- a form used to record and preserve a person’s fingerprints. Whorl- a fingerprint pattern that resembles a bull’s-eye

Review1. What is a delta?

2. How many deltas does an arch have? Loop? Whorl?

3. How can you tell the difference between a plain and

central pocket whorl?

4. What is another name for a hidden print

5. How many people on Earth have the same fingerprints as you?

6. What is this print? (Right Hand) 7. What is the most common type of print

8. What is the center of a loop and whorl called?

How do our fingerprint patterns compare to the

expected averages?

It’s time to makesome prints!

Avoid Partial Prints

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

Study Your Fingerprints Activity

Let’s determine the rate of occurrence for our fingerprint patterns ...

Pattern # Total Prints %

Arch

Loop

Whorl

How do our results compare to the averages?

60% - Loops 35% - Whorls 5 % - Arches

__% - Loops __% - Whorls __% - ArchesWrite a paragraph on your worksheet that summarizes our results.

Let’s determine the rate of occurrence to compare males vs. females.

Pattern#

Male#

FemaleTotal

Prints%

Arch

Loop

Whorl

Which pattern is most common pattern among the males in this class?

Which is most common pattern among the females?

How do the averages for each sex compare to the expected averages?

Forensic Science

T. Trimpe 2007 http://sciencespot.net/

Fingerprint visibility• Latent fingerprint- earlier stated was invisible to the eye since they are

just perspiration and sometimes oil. – Composed mainly of water (95%) and 5% other substances –

chemicals used to make these visible react with some of these substances

• Visible Prints: made by fingers touching a surface after ridges have been in contact with colored material: BLOOD, PAINT, GREASE, INK

• Plastic Prints are ridge impressions left in soft material- putty, wax, soap, or dust.

• Locating visible prints are easier being visible and distinct to the eye.

• Latent prints are more difficult and require use of technologies and techniques that will make the print visible.

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.

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.

METHODS OF DETECTING LATENT FINGERPRINTS

• THE METHOD OF CHOICE WILL DEPEND ON THE SURFACE BEING LIFTED OR TESTED.

• Hard and non-absorbent surfaces (glass, mirror, tile, and painted wood) require different approaches than soft and porous- paper, cloth, or cardboard.

• The most challenging thing an examiner faces is location of latent prints.

Visualization of Latent Prints

• On hard surfaces:– Powder

• Grey or black• Florescent• Magnetic

– Superglue – Lighting Techniques

• On soft surfaces:– Iodine fuming

• Nonpermanent visualization

– Ninhydrin• Reacts with proteins

– Gentian violet• Binds to cells and oils on tape

Ninhydrin

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.

Bottom Right: http://www.forensicsrus.com/images/SupergluePrint.jpg

Magnetic powder can also be used to reveal latent prints. This type of powder works better on shiny surfaces or plastic baggies or containers.

Top Left: http://www.stapletonandassociates.com/images/MagPowder.jpg

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

Click the icon to view the Crime 360Super Glue Video

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

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.

Fingerprint Powders• Commercially available in a

variety of colors and textures (photographing)

• Lightly applied to nonabsorbent surfaces with camelhair brush will ADHERE TO PERSPIRATION RESIDUES AND BODY OILS.

• Black and gray for photographing on surfaces- produce contrast.

Fluorescent Powders

• Fluorescent powders that fluoresce under ultraviolet light- used when color or pattern of background obscures visibility of the print. (plaid, newsprint, etc).

• Prints are typically not tape lifted, but photographed and digitized or transferred to a computer for analysis

Ultraviolet Imaging Systems• Light sources can be used to

locate prints which can then be enhanced and lifted using other methods. This saves time and energy by narrowing a search.

• Reflected Ultraviolet Imaging System- locates prints on nonabsorbent surfaces without chemical or powder treatments.

• When UV light strikes the fingerprint, light is reflected back to the viewer- differentiating the print from its background surface.

Ultraviolet Imaging Systems

Latent fingerprint on Painted Wall.Illustration of Contrast Effect due to variation of illumination angle.

Depending on what angle the user holds the light, a print can either appear white or black.

Untreated Oily Print on sticky side of Duct (Duck) tape.

35mm Black and White film.Scene Scope excels at detecting prints on surfaces that a forensic light source would find difficult or impossible.

Ultraviolet Imaging Systems

• Hand held Forensic Light Sources

CHEMICAL METHODS FOR VISUALIZING LATENT PRINTS

Iodine fuming• Iodine is a solid crystal that when heated, turns into

a vapor without passing through a liquid phase– this transformation is called sublimation.

• Suspect material is placed in an enclosed cabinet with iodine crystals

• Once heated, vapors fill the chamber and combine with amino acids in the latent print to make it visible.

• Iodine prints are not permanent and begin to fade once fuming is stopped. The print may be “fixed”– IT IS NECESSARY TO PHOTOGRAPH

IMMEDIATELY• Can be fixed with 1% solution of starch in water

applied by spraying- this will turn blue and last for several weeks or longer.

Super Glue Fuming• Super Glue fuming- works

great on nonporous surfaces- metals, leather, plastic bags.

• Created when superglue is placed on a hot plate.

• Heating produces vapors that polymerize on the print.

• Fumes and object contained within an enclosed chamber for up to 6 hrs.

• Produces white latent print.• The print may be enhanced

with a conventional powder

Gentian Violet• Once the standard for lifting

latent prints on sticky surfaces like tape – has now been replaced by a commercial product called “Sticky-Side Powder”

• The dark purple dye stains sebaceous material (oil) and skin cells which have sloughed off of the person's fingers and palms and which have stuck to the adhesive side where the tape was touched.

Ninhydrin• One of the major components of

fingerprints is amino acids. Several substances bind to them, but ninhydrin is particularly effective.

• It is sprayed or poured onto the evidence, and a permanent pink and purple fingerprint results.

• On the downside, it is toxic and causes blinding headaches if inhaled

Ninhydrin Reaction

Lifting Your Own Prints Activity

A Closer Look at Fingerprints

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

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

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.

As we have learned in our first lesson, a fingerprint is made of a series of ridges and valleys on the surface of the finger. 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.

Fingerprint IdentificationWhen minutiae on two different prints match, these are called points of similarity or points of identification. At this point there is no international standard for the number of points of identification required for a match between two fingerprints. However, the United Kingdom requires a minimum sixteen points while Australia requires twelve.

Automated Fingerprint Identification System (AFIS)

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

AFIS is a computerized system capable of reading, classifying, matching, and storing fingerprints for criminal justice agencies. Quality latent fingerprints are entered into the AFIS for a search for possible matches against the state maintained databases for fingerprint records to help establish the identity of unknown deceased persons or suspects in a criminal case.

IAFIS• INTEGRATED AUTOMATED FINGERPRINT

IDENTIFICATION SYSTEM

• Large database of fingerprint collections- using individual characteristics of fingerprints converted into DIGITAL MINUTIAE: ridge endings, and branching.

• Location and relationship of minutiae in a digitally recorded geometric pattern

– A computer can make thousands of fingerprint comparisons in a second.

• IAFIS does not make final verification of print identity, but rather flags prints with the closest correlation to the search prints.

• ALLOWS CRIMINAL INVESTIGATORS TO SPEND LESS TIME DEVELOPING SUSPECT LISTS AND MORE TIME INVESTIGATING SUSPECTS GENERATED BY THE COMPUTER.

• Fingerprints are voluntarily submitted to the FBI by local, state, and federal law enforcement agencies. These agencies acquire the fingerprints through criminal arrests or from non-criminal sources, such as employment background checks. The FBI then catalogs the fingerprints along with any criminal history linked with the subject.

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!

http://cnx.org/content/m12574/latest/properties.jpg

Ridge Characteristics

Crossover

Core

Bifurcation (fork)

Ridge ending

Island

Delta

Pore

Scar

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

How many ridge characteristics can you identify in this fingerprint?

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

How many ridge characteristics can you identify in this fingerprint?

Ending Ridge

Core

Island or Dot

Fork or Bifurcation

Short Ridge

Bridge

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

Studying Minutiae Activity

Putting it all together Activity