Transcript FingerPrint Unit Notes

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.
Arch
Plain arch
Tented arch
Loop
Radial Loop
Ulnar loop
Whorl
Plain whorl
Central pocket whorl
Double loop whorl
Accidentical
Interesting Info
Fingerprint Factoid:
60% of people have loops, 35% have whorls,
and 5% have arches
Did you know?
Dactyloscopy is the study of fingerprint identification.
Police investigators are experts in collecting
“dactylograms”, otherwise known as fingerprints.
Arches
Arches 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.
Spike or “tent”
Plain Arch
Ridges enter on one side and
exit on the other side.
Tented Arches
Similar to the plain arch,
but has a spike in the center.
Loops
Loops 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.
Whorls
Whorls 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.
Plain
Whorl
Central
Pocket
Whorl
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.
Whorls – Part 2
Double Loop Whorl
Accidental Whorl
Delta
Delta
Double loop whorls are
made up of any two loops
combined into one print.
Accidental whorls contain
two or more patterns (not
including the plain arch), or
does not clearly fall under any
of the other categories.
Identify each fingerprint pattern.
Right Hand
Left Hand
Right Hand
Right Hand
Left Hand
Fingerprint Activity
Fingerprint Unit Vocabulary
Arch- 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
Review
1. 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 make
some prints!
Avoid
Partial
Prints
GOOD PRINT
Get 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
Arch
Loop
Whorl
#
Total Prints
%
How do our results compare to the averages?
60% - Loops 35% - Whorls 5 % - Arches
__% - Loops __% - Whorls __% - Arches
Write a paragraph on your worksheet that summarizes our results.
Let’s determine the rate of occurrence
to compare males vs. females.
Pattern
#
Male
#
Female
Total
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
Some investigators use fluorescent powder and UV lights to help
them find latent prints on multi-colored or dark surfaces.
Magnetic powder can also be used to reveal latent prints. This
type of powder works better on shiny surfaces or plastic baggies
or containers.
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.
Click the icon to
view the Crime 360
Super Glue Video
Top Left: http://www.stapletonandassociates.com/images/MagPowder.jpg
Bottom Left: http://www.ok.gov/osbi/images/ninhydrin%20print.jpg
Bottom Right: http://www.forensicsrus.com/images/SupergluePrint.jpg
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 surfacesproduce 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 viewerdifferentiating 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 surfacesmetals, 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
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.
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.
1Introduction
to Basic Ridgeology by David Ashbaugh, May 1999
Image from http://www.cs.usyd.edu.au/~irena/minutia.gif
Fingerprint Identification
When 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)
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.
http://www.fdle.state.fl.us/CrimeLab/images/fingerrint%20comparison%20for%20afis.jpg
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.
•
Ridge Characteristics
Use these characteristics as points of identification when comparing fingerprint
samples. The more points you can find in common, the better the match!
Ridge Characteristics
Crossover
Core
Bifurcation (fork)
Ridge ending
Sca
r
Island
Delta
Pore
http://cnx.org/content/m12574/latest/properties.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
http://www.dkfz.de/tbi/projects/bmcv/images/iu_it246_04s_fingerprint1.jpg
Try It!
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.
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