Fingerprints
Fingerprints
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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Fingerprints
Fingerprints
All fingers, toes, feet, and palms are covered
in small ridges.
These ridges are arranged in connected units
called dermal, or friction, ridges.
These ridges help us get or keep our grip on
objects.
Natural secretions plus dirt on these surfaces
leave behind an impression (a print) on those
objects with which we come in contact.
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Fingerprints
There are 3 main fingerprint patterns found in
the human population:
Loops: found in 60% of the population
Whorls: found in 30% of the population
Arches: found in 10% of the population
A typical loop must have one or more ridges
that enter from one side, loop, and then exit
from the same side.
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Fingerprints
October 4, 2011: Activity – page 77
#1
Look at your fingerprints under the
magnifying glass. Draw each of your prints in
the boxes on the worksheet. Figure out
whether they have arches, whirls, or loops.
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Fingerprint Analysis – page 77 - # 2
 Inkprint all of your fingerprints
 Students work in groups of four: Compare your
fingerprints to the other people in your group
 1. What were some similarities in your group?
 2. What were some differences in your group?
 3. What are some problems you can foresee when using
fingerprints to identify people?
 4. What are some questions you have that you want
answered by the end of this unit?
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Fingerprints
Fingerprints
AFIS
The Automated Fingerprint Identification System—a
computer system for storing and retrieving fingerprints
Established in the 1970s
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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Fingerprints
Fingerprints
Fingerprint Minutiae
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Fingerprints
LOOP
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WHORL
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ARCH
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Fingerprints
Fingerprints
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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Fingerprints
Loop
A loop must have one or more
ridges entering and exiting
from the same side. Loops
must have one delta. A double
loop is made of two loops.
Types
Radial—opens toward the
thumb
Ulnar—opens toward the
“pinky” (little finger)
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Fingerprints
Whorl
A plain or central pocket
whorl has at least one ridge that
makes a complete circuit. 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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Fingerprints
Primary Classification
The Henry-FBI Classification System
Each finger is given a point value.
right
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Fingerprints
Primary Classification, continued
Assign the number of points for each finger that has a whorl and
substitute into the equation:
right
index
right
ring
left
thumb
left
middle
left
little
+1
=
right
thumb
right
middle
right
little
left
index
left
ring
+1
That total number is your primary classification number.
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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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Fingerprints
Latent Prints
Latent fingerprints are those that are not visible to the
naked eye. These prints consist of the natural secretions
of human skin and require development for them to
become visible.
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Fingerprints
Developing Latent Prints
Developing a print requires substances that interact with secretions,
causing 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 with the background.
Iodine—fumes react with oils and fats to produce a
temporary yellow-brown color.
Ninhydrin—reacts with amino acids to produce a
purple color.
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Fingerprints
Iodine Fingerprint
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Fingerprints
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
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Other Prints, continued
Palm—friction ridges can be
identified and may be used
against suspects
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Fingerprints
Other Prints, continued
Footprints are taken at birth
as a means of identification of
infants.
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Other Prints, continued
Earprint catches murderer
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.
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Fingerprints
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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