Fingerprinting
Forensic Science
Forensic Science
Fingerprinting
Is it a match?
• You will be given 2
prints.
• Compare the second
print to this print.
• Can you determine if it
is a match?
Major patterns
What are the distinguishing patterns of
these fingerprints?
How would you describe them?
Fundamental Principles of Fingerprints
An individual
characteristic.
Unchanged during an
individual’s lifetime.
Characteristic ridge
patterns
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Why do we have fingerprints?
• Provides better grip
– Called dermal or friction ridges
• ? Makes perspiration easier on a hairless
surface
• ? Improves sense of touch
Skin
• Epidermis (outer skin)
has 3 layers
– Peridermal
– Intermediate
– Basal
• Dermis (under layer)
– Amorphous fiber
• Basal Layer – new skin
cells form
Prints form in the fetus
• Forms between the 10th – 17th week
• Determined for life
• Basal layer –
– Forms new skin cells
– Grows faster than the upper layers and the dermis
– Folds into interconnected ridges
Prints
• Natural secretions - water, oils, salt
• Dirt
• Provide an impression on contacted surfaces
• Also on toes, soles of the feet, palms
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Fingerprint formation
Important Terms
•
•
•
•
Dactyloscopy
Patent fingerprint
Plastic fingerprint
Latent fingerprint
• Epidermal
• Basal layer
• Dermis
•
•
•
•
•
•
Arch
Loop
Whorl
Delta
Core
Minutia patterns
Resources
• http://finger• http://www.crimemuse
prints.com/index.html
um.org/library/forensic
s/fingerprints.html
• http://en.wikipedia.org/
wiki/Fingerprint
• http://www.livestrong.c
om/article/287440-thedevelopment-offingerprints-in-babies/
Major visual patterns
Loops
65% population
Arches
5% population
Whorls
30% population
Classification of Fingerprints
• Three basic patterns:
– Loop
• 65%
– Whorls
• 10-20%
– Arches
• 5%
– Racial variations
• African (more arches), European (more loops), Asians/Orientals
(more whorls)
Loop
 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?
Delta
Whorl
 Whorls have at least two deltas
and a core.
 Four Groups
 Plain
 Central Pocket
 Double Loop
 Accidental
Plain Whorl
Whorl
• Central Pocket
Whorl
• Double loop
Whorl
• Accidental
Arch
• 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
Identify each fingerprint pattern.
Right Hand
Left Hand
Right Hand
Right Hand
Left Hand
It’s time to make
some prints!
Avoid
Partial
Prints
GOOD PRINT
Get as much of the top part
of your finger as possible!
Henry-FBI Classification
• Developed by Edward Henry
• Allowed all sets of ten fingerprints in the
world to be divided into 1024 groups
• Secondary and more complex classifications
were created to allow for more groups
Primary Classification
The Henry—FBI Classification
Based on WHORLS
Each finger is given a point value
right
left
Primary Classification
Assign the number of points for each finger that has a
whorl and substitute into the equation:
right
index
right
ring
left
thumb
left
left
middle little + 1
right
thumb
right
middle
right
little
left
index
left
ring
+1
That number is your primary classification number
=
Individualization
• Henry-FBI Classification
– Narrows into a group
• Ridge Classification
– Uses minutiae to individualize fingerprints
– In U.S. there are no legal requirements for # of
points
– Criminal courts accept 8 to 12 points
– 150-200 minutiae in a good rolled print
Fingerprint Minutiae
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Ridge Characteristics
Minutiae—characteristics of ridge patterns










Ridge ending
Short ridge
Dot or fragment
Bifurcation
Double bifurcation
Trifurcation
Bridge
Island
Enclosure
Spur
Comparison
Can you
identify the
points?
Fingerprint Minutiae
How are fingerprints analyzed?
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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Latent Prints
 Latent fingerprints
 Hidden
 Natural secretions of human skin
 Require development for them to become visible
 Most secretions come from glands:
 Eccrine—largely water with both inorganic
(ammonia, chlorides, metal ions, phosphates) and
organic compounds (amino acids, lactic acids, urea,
sugars). Most important for fingerprints.
 Apocrine—secrete pheromones and other organic
materials.
 Sebaceous—secrete fatty or greasy substances.
Developing Latent Prints
 Requires substances that interact with
secretions
 Attempt more than one technique, done in a
particular order so as not to destroy the print
Iodine Fingerprint
Ninhydrin Fingerprint
Cyanoacrylate 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
Lips—display
several common
patterns
 Short vertical
lines
 Short horizontal
lines
 Crosshatching
 Branching
grooves
Other Prints
Palm—friction
ridges can be
identified and may
be used against
suspects
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Other Prints
Footprints are taken at
birth as a means of
identification of infants.
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Other Prints
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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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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Other Prints
The blood vessel
patterns in the eye
may be unique to
individuals. They are
used today for various
security purposes.
Which
fingerprints are
matches?
Match the ones
that are made by
the same finger.
In some cases,
one print may
appear two or
three times.
Matching can be facilitated by digital enlarging and
comparing cropped areas, or by enlarging with a
photocopier and using a transparency overlay.
A = G = S This one is interesting; there are three separate
impressions of the same finger with some very unique
features.
B = no match C = no match D = no match E = T
F=JH=R
I = no match
K=O
L = no match
M=PN=Q
Case Study: Madrid Bombings. Comparison of
fingerprints
Mayfield prints
Prime suspect