Fingerprints
The Study of Fingerprints:
Dactyloscopy
What was used before f’prints?
• Alphonse Bertillion (1883)
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French policeman
Detailed description of the suspect
Anthropometry
11 measurements
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Height
Expanse of his arms
Circumference of his head (using calipers)
Length of right ear
Length of left foot
Length of selected fingers
Size and shape of nose
Tilt of forehead
Scars and blemishes
– The possibility that 2 people would have the same
measurements was 1 in 4 million
• Ex: Will West (1903 – Leavenworth prison)
History
• Bertillion system (Bertillonage) was used for
20 years (used to successfully ID 800
criminals)
• William Herschel – India
– Required that native sign for contracts using an
imprint of their right hand
• Henry Fauld
– Scottish physician
– Published in 1880 – skin ridge patterns could be
important for the ID of criminals
• Francis Galton –
– 1892 published “Finger Prints”
– Discussed the anatomy of prints
– Recommended 3 categories
• Loops, arches, whorls
• No 2 fingerprints are alike
History
• Creation of Classification systems
– Needed a way of filing 1000’s of prints in a
logical/searchable sequence
• 1891 – Dr. Juan Vucetich (Argentinean
police officer)
– Devised a system that is still used by most
Spanish speaking countries
• 1897 – Sir Edward Richard Henry
System
– Adopted by Scotland Yard and most
English speaking countries
• In the US – 1901
– Officially adopted for applicants for the
History
• In the US (cont.)
• 1924 – fingerprint records were combined to
form the identification records of the newly
formed FBI
– Largest collection of fingerprints in the world
• 1999 – US v. Byron C. Mitchell
– Eastern PA
– Defendant claimed that fingerprints could not be
unique under the Daubert ruling
– Judge came back with a verdict which stated
• Human friction ridges are unique and permanent
• Human friction ridge skin arrangements are unique and
permanent
History
• Daubert
– Whether the scientific technique or theory
can be (and has been) tested
– Whether the technique or theory has been
subject to peer review and publication
– The techniques potential rate of error
– Existence and maintenance of standards
controlling the techniques operation
– Whether the scientific theory or method
has attracted widespread acceptance within
a relevant scientific community
Fundamental Principles
of Fingerprints
 A fingerprint is an individual
characteristic.
 A fingerprint will remain
unchanged during an individual’s
lifetime.
 Fingerprints have general
characteristic ridge patterns that
permit them to be systematically
classified.
Stick to the Fundamentals
• Three (3) Principles of Fingerprints
• 1st – A fingerprint is an individual
characteristic;
– no two fingers have yet been found to
possess identical ridge characteristics
– Individuality is determined by the number,
ID and relative location of its ridge
characteristics (minutiae)
• There are as many as 150 individual
characteristics on the average fingerprint
Stick to the Fundamentals
• Three (3) Principles of Fingerprints
(cont.)
• Unfortunately - most prints only
come in partials
• 1973 – International Association of
Identification
– Concluded, “no valid basis exists for
requiring a predetermined minimum
number of friction ridge characters
which must be present in 2
impressions in order to establish
positive identification”
Ridge Characteristics
Minutiae—characteristics of ridge patterns
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Ridge ending
Short ridge
Dot or fragment
Bifurcation
Double bifurcation
Trifurcation
Bridge
Island
Enclosure
Spur
Fingerprint Minutiae
Three Principles (cont.)
• 2nd – A fingerprint will remain
unchanged during an individual’s
lifetime
– Epidermis and Dermis
– Fingerprints are a reproduction of skin
ridges (used for friction/firmer grasps)
– Dermal papillae – boundary between the
dermis/epidermis
• Determine the form and pattern of the
ridges on the surface of the skin
• Develop in the fetus
Three Principles (cont.)
• Each skin ridge has a single row
of pores
– openings for ducts leading form
the sweat glands (perspiration)
• Oils come for other parts of the body
(no oil glands on hand/feet)
– Both the sweat and oil can lead to…
• Latent fingerprints –
– Prints that are invisible to the naked eye
• Impossible to change one's
fingerprints
– Ex: John Dillinger
Epidermal Ridges of Thick Skin
Three Principles (cont.)
• 3rd – Fingerprints have general ridge
patterns that permit them to be
systematically classified
• 3 classes –
1. loops (60-65%) – ridge lines that enter from
one side of the pattern and curve around to
exit from the same side of the pattern
• Ulnar – opens toward the little finger
• Radial – opens toward the thumb
• Type lines – two diverging lines that surround
the loop
• Delta – all loops must have one
– The ridge point at or nearest the type line divergence
– located at or directly in front of the point of
divergence
• Core – approximate center of the loop
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?
Three Classes (cont.)
2. whorls (30-35%) – ridge patterns that are
generally rounded or circular in
shape…must have:
– type lines and at least 2 deltas
– At least one ridge that makes a complete
circuit
– Spiral, oval or any variant of a circle
– 4 types:
• plain whorl
– If you can draw an imaginary line between the 2 deltas
contained within these 2 patterns…and have the line
touch any one of the spiral edges
• pocket loop
– If no such edge is touched the pattern is a central
Whorl
Whorl
 A plain or central pocket whorl has at least one
ridge that makes a complete circuit. A double loop
is made of two loops. An accidental is a pattern not
covered by other categories. Whorls have at least
two deltas and a core.
 Types
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Plain
Central Pocket
Double Loop
Accidental
Three Principles (cont.)
• Whorls (cont.)
– Double loop – 2 loops combined into
one fingerprint
– Accidental –
• contains 2 or more patterns (not
including the plain arch)
• Pattern not covered by other categories
Three Classes (cont.)
• Arch (5%) – ridge lines that enter the
print from one side and flow out the
other side
– Do not have type lines, deltas or cores
– Least common
– Plain arch – simplest of all
• See definition above
• Form a wavelike pattern
– Tented arch
• Instead of rising smoothly at the center there's
a sharp spike or the ridges meet at an angle
that is less than 90 degrees
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
Classification of Prints
• Original Henry system
• FBI System
– Primary Classification
• All the fingerprint cards in the
world can be divided into 1,024
groups
• Pair up fingers
Classification of Prints (cont.)
• FBI System (cont.)
R. Index R. Ring
L. Thumb
R. Thumb R. Middle R. Little
L. Middle
L. Index
L. Little
L. Ring
– Based on the presence/absence of a
whorl pattern and then assigned a
specific value
• first pair - 16
• Second pair – 8
• Third pair – 4
• Fourth pair – 2
• Last/fifth pair – 1 (one)
– Finger with an arch or loop pattern is
assigned a zero (0)
Classification of Prints (cont.)
• FBI System (cont.)
R. Index R. Ring
L. Thumb
R. Thumb R. Middle R. Little
L. Middle
L. Index
L. Little
L. Ring
– After values are taken for all 10
fingers….they are totaled and 1 (one)
is added to the numerator and the
denominator
– The resulting fraction is the primary
classification
– 25% of the population falls into the
1/1 category (all their fingers have
loops or arches)
AFIS
• Automated Fingerprint Identification
Systems
– A computer scans and digitally encodes
fingerprints so they can be subject to high
speed computer processing
– determines the relative position and
orientation of the minutiae
– “Uses automatic scanning devices that
convert the image of a fingerprints into
digital minutiae that contain data showing
ridges at their point of termination (?) and
the branching of ridges into 2 ridges (?)”
– Makes no final decisions…that is left up
the fingerprint expert
Kinds of Crime Scene Prints
• Visible prints –
– made by fingers touching a surface
after ridges have been in contact with
a colored materials (blood, paint,
etc.)
• Plastic Prints –
– ridge impressions left on a soft
material (putty, wax, soap or dust)
• Latent/invisible prints –
– caused by the transfer of
perspiration/oils on finger ridges to
the surface of an object
Methods of Detection
• Method of choice depends on the
type of print
• Hard/non-absorbent surfaces
require different methods than
soft/porous materials
– Powders and Super Glue ® vs.
chemical treatments
• Most difficult aspect of fingerprint
examination?
Methods (cont.)
• Visualization
– RUVIS (Reflected Ultraviolet
Imaging System)
• Locates prints on most nonabsorbent
surfaces without chemical or powders
• UV light strikes the fingerprints, is
reflected back to the viewer, then
converted into visible light by an image
intensifier
Visualization (cont.)
• Fingerprint powders
– Applied to nonabsorbent surfaces
with a camel hair or fiberglass brush
• Adheres to oils/perspiration
– Gray and black powders are adequate
for most latent print work
– Magnetic sensitive powder
• Useful for leather and rough plastics
– Fluorescent powders
Visualization (cont.)
• Iodine fuming (hardly used anymore)
– Heat iodine crystals  vapor without passing thru
a liquid phase (?)
– How does it work?
• Put suspect material in a cabinet with the heated
iodine crystals
• Vapors fill the chamber and combine with
constituents of the latent print to make it visible
• Reason?
– No one knows for sure
– fatty oils or residual water left on a print from
perspiration
• Problems
– Not permanent -- fades once fuming is stopped
• Therefore?
– Must be photographed immediately
– Or fixed with a 1% starch-water solution that is
sprayed on
» The print will then turn blue and last weeks-months
Visualization (cont.)
• Ninhydrin (another chemical)
– Method of choice for most examiners
• Extremely sensitive and easy to apply/use
– Forms a purple-blue color with amino acids
present in perspiration
– Commonly sprayed on to porous surfaces
– Prints begin to appear in an hour or 2
– Development can be hastened if the treated
specimen is heated in an oven or hotplate at
80-100oC
– Has been used on papers as old as 15 years
Visualization (cont.)
• Physical Developer (yet another
chemical)
– Silver nitrate-based liquid reagent
– Useful for turning up prints on porous
surfaces that had been wet
– Problem?
• PD washes away any trace of protein
that may be on/a part of the
print/surface
Visualization (cont.)
• Super Glue ® Fuming
– 1982
– Good for detection on nonporous surfaces
such as metal, electrical tape, leather and
plastic bags
– Fumes can be created when the glue is
placed on cotton treated with NaOH (as
well as heating the glue)
– Put in an enclosed chamber for approx. 6
hours and the fumes from the glue will
adhere to the latent print
• Gives the print a white-appearance
– Now have hand held wands that do the
same thing…can direct the fumes to
particular places (ex: car, etc.)
Visualization (cont.)
• Fluorescence
– Def: when a substance absorbs light and
reemits the light in wavelengths longer
than the illumination source
– Laser light
• Perspiration contains a variety of components
that fluoresce when exposed to lasers
• Drawback?
– Only small amounts of perspiration components are
present in the fingerprint
• The examiner wears safety goggles containing
optical filters
– The goggles will absorb some of the light, but let the
wavelengths at which prints fluoresce pass thru
Visualization (cont.)
• Fluorescence and lasers (cont.)
– Treat fingerprints with chemicals that
bring about fluorescence when
exposed to lasers
– Apply:
• zinc chloride after ninhydrin treatment
• dye rhodamine 6G after Super Glue
fuming
Visualization (cont.)
• Alternate Light Source
– Because of chemically induced
fluorescence, lasers no longer needed
– High intensity lights are sufficient
• Quartz halogen, xenon arc or indium can
be focused in a suspect areas thru a fiber
optic cable
• Can be passed thru a number of filters
– more flexibility as to the wavelength of
light to be aimed at the print
– Cheaper and more portable
Visualization (cont.)
• Common fingerprint agents do not
interfere with DNA testing
methods
• Recommended that in cases
involving items with material
adhering to surfaces that will
require further lab exams,
fingerprint processing should not be
performed at the crime scene
Preservation of Developed Prints
• For future comparison
– Take a picture…it’ll last longer
• If the object on which the print is located is
small enough to move/transport…take it
wichya
– Cover it in cellophane
• If the print is a part of an object is too large to
move, it can be lifted
– Preserve the print with powder
– Apply broad adhesive tape onto the print (evenly)
– Place the tape/print on a properly labeled card that
shows contrast
– Also able to be used: adhesive-backed clear plastic
sheet that is attached to a colored cardboard
backing