Students will explore fingerprint identification
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Dactylscopy
Ridge characteristic
Minutiae
Loop print
Whorl print
Arch print
IAFIS
Ridge count
Bifurcation
Double bifurcation
Lake/enclosure
Spur
Short ridge
Island/eye
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Dot
Bridge/crossover
Ridge ending
Latent print
Visible print
Plastic print
 Dactylscopy is the study of fingerprints. This
study began in the 1800’s.
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First Principle: A fingerprint is an individual
characteristic, no two fingers have identical
ridge characteristics
 It is not the shape of a print that is individual, but
the number, location and shape of specific ridge
characteristics
 Specific ridge characteristics are called minutiae
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Second Principle: A fingerprint will remain
unchanged during an individual’s lifetime
 A fingerprint can be obscured by deep tissue
damage such as scars or burns
 Scars may be useful as points of identification
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Third Principle: Fingerprints have general
ridge patterns which permit them to be
systemically classified.
 Classifying the general pattern of fingerprints
allows them to be stored in a filing system, which
then can be retrieved for comparison.
 Modern technology allows this process to be
transformed to a computer system- IAFIS
There are three levels or degrees of
classification, with each degree being more
specific
 The first degree of classification is based on the
overall pattern of each print, loops, whorls and
arches.
 any whorl patterns. It is called the 10 print
classification system.
 Second degree is the identification of minutiae
 Third degree is the identification of pores
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Prints have overall patterns. They are called
either loops, whorls or arches.
These overall patterns are not unique. They
are class evidence, not individual evidence.
If all fingers have been printed, then the 10print classification can be determined.
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Developed by Edward Henry and modified by
the FBI.
Breaks up all possible sets of fingerprints to
be divided into a possible 1,024 groups.
Based on a whorl pattern – must have ALL
fingers printed to determine
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Formula:
Top: Rt index(16)+ rt ring(8)+ Left thumb(4)+ Left
middle(2) + left little(1) + 1 =
Bottom: rt thumb (16)+ rt middle (8)+ rt little(4) +
left index(2)+ left ring(1) + 1 =
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(See next slide)
Therefore, if a whorl pattern is present on any
of the fingers, it is assigned a numerical
value.
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The result is written as a fraction
The complete code exactly describes the
print in a way people and machines can
understand and file
This presents examiners with a manageable
list of possible matches for the fingerprint.
Computer matching of fingerprints is used to
make the first big cut of matches, after this
manual comparison may still be needed.
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Fingerprints can be classified into three basic
patterns, loops, whorls and arches
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Most common pattern, with 65% of all
fingerprints having loops
Fingerprint pattern with one or more ridges
entering from one side, curving, then going
out from the same side entered
 Loops have two focal points, delta and core
▪ Delta- triangular area found in all loop and whorl
patterns
▪ Core- area found near the center of all loop and whorl
patterns
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There are two subgroups to the loop, the
radial loop and the ulnar loop
▪ Radial loop- ridges flow in the direction of the thumb (
radius)
▪ Ulnar loop- ridges flow in the direction of the
▪ little finger (ulna)
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European ancestry tend to have more loop
patterns on their fingerprints
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Second most common pattern, occurring in
30-35% of all fingerprints
Fingerprint pattern with at least two deltas
and a core. Whorls take the form of a spiral,
shell, circle, target or eye.
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There are four types of whorls
 Plain
 Double whorl Central Pocket Accidental
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Asian and Oriental ancestry tend to have
more whorls patterns on their fingerprints.
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Arches are the least common and the simplest of
fingerprint patterns, occurring in 5% of fingerprints
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Fingerprint pattern that has no delta or core. All ridges enter
one side and exit the other.
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Arches are subdivided into two distinct
groups, plain and tented
 Plain-Ridges tend to rise in the center of the
pattern, forming a wave-like pattern
 Tented – contain a sharp spike in the ridges, or the
ridges meet at an angle less than 90 degrees.
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African American ancestry tend to have more
arch patterns on their fingerprints.
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One way to start to individualize prints is to
do a ridge count. A straight line is drawn
from the central focus to the center of the
delta. The number of ridges this line crosses
is counted and that number = the ridge count
This works best with loops and whorls where
deltas are clearly present.
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To individualize fingerprints you must use the
fine structure of ridge characteristics, or
minutiae.
There are several classes of minutiae to help
individualize fingerprints.
For each type, refer to your balloon print and
find one example of each type
 Bifurcation- occurs when a ridge splits or forks
into two separate ridges
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Double bifurcation-occurs when a ridge splits or
forks into two separate ridges, and then splits again
into two separate ridges
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Ridge End - abrupt termination of any ridge.
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Lake or enclosure -occurs when a single ridge line
bifurcates, then quickly reconnects and continues as
a single ridge
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Island or eye - short ridges that simply start
and stop and don’t connect to any other ridge
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Dot - a very short island, of basically equal
length and width
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Bridge -short ridge that runs between two
other parallel ridges, sometimes called a
“railway tie”
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Spur- a special bifurcation where one resulting ridge
is considerably shorter, ending near the original
split/fork
See the pores? This
is the 3rd degree of
fingerprint
idenification.
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There are no legal requirements in the United
States on the number of minutiae and their
relative location (points) that must match
before deciding that a fingerprint belongs to
a certain individual.
There are 150-200 minutiae in a properly
rolled print.
Criminal courts will generally accept 8-12
points of similarity as sufficient proof. An
newer acceptance level of 10 is typical.
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Tru TV fingerprint game
http://www.trutv.com/shows/forensic_files/g
ames/fingerprint/index.html
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The Integrated Automated Fingerprint
Identification System (IAFIS) is a system
maintained by the FBI.
IAFIS provides automated fingerprint search
capabilities, latent searching capability,
electronic image storage, and electronic
exchange of fingerprints and responses.
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IAFIS maintains the largest biometric
database in the world, containing the
fingerprints and potential corresponding
criminal history information for more than 47
million subjects.
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This approach has revolutionized criminal
investigative used of fingerprints. A computer
can make thousands of comparisons in a second,
thus increasing the chances of finding a match in
a far shorter time than was previously possible.
Shortly after being brought on-line for the first
time in 1985 the Los Angeles Police
Department's IAFIS helped bring to justice the
multiple killer known as the Nightstalker.
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The device used for scanning live fingerprints
into AFIS is called Live Scan. The process of
obtaining the prints by way of Live Scan
employs rolling prints or placing flat
impressions onto a glass plate above a
camera unit.
The process of obtaining prints by placing a
ten print card (prints taken using ink) onto a
flatbed or high-speed scanner is called
CardScan.
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A photograph of the print from the crime
scene is scanned into a computer.
The image of the fingerprint is compared
with the computerized database of prints and
a list of possible "hits" is produced.
It is then up to the fingerprint expert to make
the final decision as to whether there is
match or not.
•Plastic prints are impressions of a fingerprint left in a soft substance such as, wax, soap, putty, gum, stamps, candy bar, or fresh paint. They are also
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Plastic prints are impressions of a fingerprint
left in a soft substance such as, wax, soap,
putty, gum, stamps, candy bar, or fresh paint.
They are also known as indented or molded
prints and are not commonly found at a crime
scene.
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Visible prints are fingerprints that have
touched colored materials such as; blood,
paint, ink, grease, chalk, mud or dust. Visible
prints are not common at a crime scene.
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Latent prints are fingerprints formed by oil
and sweat secretions deposited by a person’s
finger when they touch a surface or object.
Latent prints are invisible and must be
developed by chemical or physical means.
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To make latent fingerprints visible they must
be developed or treated to make them
visible. Once there is a visible print to work
with, the next step is to recover it and
document its location at the scene.
There are several physical and chemical
methods of visualizing latent fingerprints.
dusting, staining and chemical fuming are
common methods.
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Dusting is the most widely used method of
detecting latent finger prints. It is suitable for
hard and/or non-porous surfaces. Uses a fine
powder that adheres to the traces of oil and
sweat.
 There are several types of powders used to
develop prints examples are:
 The “developed” print can then be “lifted” by
means of clear sticky tape and collected for
analysis.
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Iodine reacts with the fatty oils from the
finger to form a visible but short-lasting print.
Iodine works best for prints on porous paper.
The print will fade over time, but as iodine
does not chemically alter the print in any way,
it can be re-applied if needed
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Ninhydrin reacts with the amino acids.
commonly used with paper and porous surfaces
can be used after iodine fuming
Stains a print over a 24 hour period. Can be sped up with
humidity and heat
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Superglue fuming: when superglue is heated it
creates fumes which bind to fingerprint oil residues.
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This makes a white permanent impression that then can be
treated with powders or fluorescent dyes to create a sharper
contrast and allows for easier lifting or photography.
Used for developing prints on non-porous surfaces such as
metals, glass, plastic articles, adhesive tape and firearms.
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Silver Nitrate reacts with the sodium chloride
(salt) from perspiration.
For very old prints, the sodium chloride may
be the only thing left so silver nitrate is the
only option.
Silver nitrate is used on porous surfaces, like
paper or wood.