T. Trimpe 2006 & Bertino
A Brief History
• Early 1800s—fingerprint
patterns first discussed
• 1892—Francis Galton
published book fingerprints
used to identify individual
Sir Francis Galton
What Is a Fingerprint?
• Ridges of skin that are created when we
are still in our mother’s womb.
• Remain the same for the rest of our lives
• Each of the ridges connect to other
ridges, forming a pattern that is unique to
• This uniqueness is used in many
forensic cases to solve crimes, as some
of the most common evidence found at a
crime scene are fingerprints.
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
• 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.
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 Loop Whorl
Plain arch Radial Loop Plain whorl
Tented arch Ulnar loop Central pocket whorl
Double loop whorl
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 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 Tented Arches
Ridges enter on one side and Similar to the plain arch,
exit on the other side. but has a spike in the center.
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.
Ulnar Loop (Right Radial Loop (Right
Loop opens toward Loop opens toward the
right or the ulna bone. 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 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
Whorls – Part 2
Double Loop Whorl Accidental Whorl
Double loop whorls are Accidental whorls contain two
made up of any two loops or more patterns (not
combined into one print. including the plain arch), or
does not clearly fall under any
of the other categories.
Identify each fingerprint pattern.
Left Hand Right Hand
Right Hand Left Hand
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
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
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.
Use these characteristics as points of identification when comparing fingerprint
samples. The more points you can find in common, the better the match!
How many ridge characteristics can you identify in this fingerprint?
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
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
• The way a suspect
print is analyzed is
that it’s compared to a
print found at a crime
scene. If there are a
certain number of
points of minutiae that
match, then a match
• Minutiae are small Examples of types of minutiae from
details that are breaks perso.orange.fr/.../types/fingerprint.ht
in the patterns of the m
ridges. No two people
have the same set of
• Latent prints- latent prints are hidden and
deposited via the secretions from skin. They are
often made visible through a number of different
• Patent prints- highly visible and made from
foreign substances such as blood. Since they
need no further visualization, they are often just
photographed to preserve the evidence.
• Plastic prints- Friction ridge impressions
deposited in a material that retains the shape
such as clay or or melted wax.
• Arches • Loops
The most commonly found types
of fingerprints are whorls, while
the least common types are
arches. Loops fall somewhere
• Whorls There is more specific types of classification
techniques, and these are just the most basic three.
For example, arches can be broken down into plain
arches or tented arches, and whorls can be broken
down into accidental whorls, or any other number of
It’s time to make
Prints Get as much of the top part
of your finger as possible!
Ten Card Example
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
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.
What Are Fingerprints?
• All fingers, toes, feet, and palms are
covered in small ridges
• Ridges help us grip objects
• Ridges are arranged in connected units
called dermal, or friction, ridges
• Fingers accumulate natural secretions
• Fingers leave create prints on objects we
Structure of Skin
Techniques For Lifting a
• Used on smooth, non-
• The area is lightly and
carefully dusted with
either a black or white
powder, depending on
the contrasting surface.
• The dust is lifted with
tape and set against a
contrasting background. Fingerprint dusting in a lab
• The print is preserved
• Suspect material is
placed in an enclosed
cabinate along with
• The crystals are heated,
and will sublimate (turn
into a gas vapor). Fingerprint visualized with
• The vapors cause the
prints to visualize.
• Ninhydrin (triketohydrindene hydrate)-
this chemical is sprayed onto a porous
surface via an aerosol can. Prints
begin to visualize an hour or two after
application, although the process can
be accelerated through heating the
• Silver nitrate- silver nitrate is sprayed
onto the porous surface and left to dry.
Then it is exposed to ultraviolet light to
visualize the prints.
Silver Nitrate spray
• Used mainly on non-porous
• Superglue is placed on cotton and
treated with sodium hydroxide.
• Fumes can also be created by
heating the glue.
• The fumes and the object are
contained in a closed chamber for
up to six hours.
• The fumes adhere to the print,
Fingerprint Forensic FAQs
• Can fingerprints be erased?
Only temporarily; they will grow back if removed with chemicals
• Is fingerprint identification reliable?
Yes, but analysts can make mistakes
• Can computers perform matches in
No, but the FBI’s Integrated Automated Fingerprint Identification
System (IAFIS or AFIS) can provide a match in 2 hours