Transcript Slide 1

Dermatoglyphics
Introduction to Fingerprint
Identification
Fingerprinting
• A fingerprint is an INDIVIDUAL
CHARACTERISTIC
– no two have yet been found to possess
identical ridge characteristics.
Fingerprinting
The foundation for its acceptance in court– the probability that two fingerprints could
match is such a low probability
– there is an estimated 64 billion different
individual prints.
– This is supported by the millions of individuals
who have had prints taken over the past 90
years in the FBI central system- no two have
ever been found to be identical
Fingerprints
• Fingerprints are a reproduction of friction
skin ridges found on the palm of the
fingers and thumbs.
• Also found on palms and soles of feet.
• Designed for firmer grasp and resistance
to slippage
Fingerprints
• FINGERPRINTS WILL REMAIN
UNCHANGED DURING AN
INDIVIDUAL’S LIFETIME
Fingerprints
• Series of lines corresponding to hills
(ridges) and valleys (grooves).
• It is the shape and form of skin ridges
seen as black lines of an inked fingerprint.
Anatomy of the Fingerprint
•
Skin is composed of layers of
cells:
•
Epidermis (outer portion) and
dermis as inner skin.
•
In a cross section- a boundary of
cells separating the epidermis
from the dermis is made up of
dermal papillae- these determine
the form and pattern of ridges on
the surface.
•
Dermal papillae develop in the
fetus and remain unchanged
during life.
Latent Prints
• Each skin ridge is populated with a single row of pores—
openings for ducts leading from sweat glands
– Perspiration and oils are discharged and deposited on surface of
skin.
– When these contact another surface- oils and perspiration are
transferred
– Leaves an impression of the finger’s ridge pattern (fingerprint)
– Invisible to the eye and referred to as latent fingerprints
Dermatoglyphics
• Individuality is not
determined by general
shape or pattern but by a
careful study of its ridge
characteristics
– (also called minutiae)
• Identity- number- and
relative location of
characteristics that impart
individuality.
Sir William Hershel - 1856
• Maybe the first to use fingerprints
• An English Chief Magistrate in India who used prints
on native contracts
Dr. Henry Foulds
• Notices finger marks on prehistoric
pottery
• Published an article in “Nature”
saying fingerprints could be
used for identification
Sir Francis Galton - 1888
Sir Francis Galton - 1888
• Sir Francis Galton, a British anthropologist and a
cousin of Charles Darwin, began his
observations of fingerprints as a means of
identification in the 1880's.
• In 1892, he published his book, "Fingerprints",
establishing the individuality and permanence of
fingerprints. The book included the first
classification system for fingerprints.
Making the Comparison
1. General ridge patterns are used to
narrow down the number of suspects
2. Specific details of the ridges are used to
make the final match
Types of Prints
Types of Prints
• FINGERPRINTS HAVE GENERAL RIDGE PATTERNS
FOR CLASSIFICATION:
• Divided into three classes:
– LOOP
– WHORL
– ARCH
• 60-65% OF POPULATION HAS LOOPS
• 30-35% WHORLS
• AND 5% ARCHES.
Loop
• Loop must have one
or more ridges
entering from one
side of the print,
recurring and exiting
from the same side.
– If loop opens toward
little finger= ulnar loop
– Opens from the
thumb= radial loop
Type-lines
• Pattern area of the
loop is surrounded by
two diverging ridges
known as type-lines.
Deltas
• The ridge point nearest the type-line
divergence is the DELTA.
– Triangular in shape.
– ALL LOOPS HAVE ONE DELTA
Core
Core = center of
the pattern.
Whorls
• Whorls- 4 distinct groups:
–
–
–
–
Plain
Central pocket
Double loop
Accidental.
• All whorl patterns have type
lines and a minimum of two
deltas.
• Plain and central pocket loop
whirl have at least one ridge
that makes a complete circuit.
• Ridge may be spiral, oval or
any variant of a circle
Arches
• Arches- least
common has 2
patterns- plain arches
and tented
• Do not have:
– type lines
– deltas
– or cores
Making the Comparison
• There are as many as
150 individual ridge
characteristics on the
average fingerprint.
– a vast majority of
prints recovered from
crime scenes are
partial impressionsshowing only a
segment of the print.
Making the Comparison
• Expert has to compare small
number of ridge characteristics
from the recovered print to the
known recorded print.
• Criteria of individuality in court
requires 8-16 matching
characteristics
• 1973 International Association
for Identification concluded “it
is the responsibility of the
examiner- based upon
experience and knowledge to
establish positive identification.
Minutiae
• Minutiae are the details in a fingerprint.
• With the minutiae a fingerprint identification can
be made.
• There are big details like starting lines, splitting
lines and line fragments.
• But there are also smaller details like pores,
incipient ridges, and line shapes.
Minutiae
• Line-unit, it exists as only one isle
with a pore.
• Line-fragment. 2 or more line-units
• A beginning or ending line.
Minutiae
•Bifurcation, a splitting line.
• Eye, two lines splitting and
meeting each other shortly after
that.
•Hook, a short splitting line.
Minutiae
•Pores, details in number, shape and size.
• Line shape, the lines vary breadth.
•Scars, the lines can not recover anymore.
• Incipient ridges, between the papillary
lines.
Minutiae
•
Creases, also permanent
• Warts, not permanent but also typical.
• Temporary damages.
• Deformation, the lines deform and fall
apart.
IAFIS
Integrated
Automated
Fingerprint
Identification
System
Large database of fingerprint collectionsusing individual characteristics of
fingerprints converted into DIGITAL
MINUTIAE: ridge endings, and branching.
Location and relationship of minutiae in a
digitally recorded geometric pattern
A computer can make thousands of
fingerprint comparisons in a second.
IAFIS does not make final
verification of print identity,
but rather flags prints with the
closest correlation to the
search prints.
IT ALLOWS CRIMINAL
INVESTIGATORS TO SPEND
LESS TIME DEVELOPING
SUSPECT LISTS AND MORE
TIME INVESTIGATING
SUSPECTS GENERATED BY
THE COMPUTER.
IAFIS
• The IAFIS maintains the largest biometric
database in the world
– containing the fingerprints and corresponding
criminal history information for more than 47 million
subjects in the Criminal Master File
• The fingerprints and corresponding criminal
history information are submitted voluntarily by
state, local, and federal law enforcement
agencies.
TYPES OF FINGERPRINTS
1. Latent fingerprint - earlier stated was invisible
to the eye since just oils and perspiration.
2. Visible Prints- made by fingers touching a
surface after ridges have been in contact with
colored material: BLOOD, PAINT, GREASE,
INK
3. Plastic Prints -are ridge impressions left in soft
material- putty, wax, soap, or dust.
METHODS OF DETECTING
FINGERPRINTS
• THE METHOD OF CHOICE WILL DEPEND ON
THE SURFACE BEING LIFTED OR TESTED.
• Hard and non-absorbent surfaces (glass, mirror,
tile, and painted wood) require different
approaches than soft and porous- paper, cloth,
or cardboard.
• The most challenging thing an examiner faces is
finding the location of latent prints.
Ultraviolet Imaging Systems
• Reflected Ultraviolet Imaging
System- locates prints on
nonabsorbent surfaces without
chemical or powder
treatments.
• When UV light strikes the
fingerprint, light is reflected
back to the viewerdifferentiating the print from its
background surface.
• UV light is converted into
visible light by image
intensifier.
Ultraviolet Imaging Systems
Latent fingerprint on Painted Wall.
Illustration of Contrast Effect due to variation of
illumination angle.
Depending on what angle the user holds the light, a
print can either appear white or black.
Ultraviolet Imaging Systems
Untreated Oily Print on sticky side of
Duct (Duck) tape.
35mm Black and White film.
Scene Scope excels at detecting prints on
surfaces that a forensic light source would
find difficult or impossible.
Ultraviolet Imaging Systems
• Hand held Forensic
Light Sources
Fingerprint Powders
• Commercially available in a
variety of colors and
textures
• Lightly applied to
nonabsorbent surfaces with
camelhair brush will
ADHERE TO PERSPIRATION
RESIDUES AND BODY OILS.
• Black, white and gray for
photographing on surfacesproduce contrast.
Only works if MOISTURE is present!
White powder on
dark surface
Magnetic Powders
• Magnetic powders- Magna Brush- since
there are no bristles there is less chance
of destroying print.
• Fluorescent powders that fluoresce under
ultraviolet light- used when color or pattern
of background obscures visibility of the
print. (plaid, newsprint, etc).
Mikrosil
• Lifting dusted prints from
irregular or curved objects
can be performed with a
casting compound called
Mikrosil.
Mikrosil
STICKY SIDE POWDER
•
Sticky-side powder is used for
developing fingerprints found on
adhesive surfaces.
•
Leaves a black print that can be
photographed easily
Cyanoacrylate (Super Glue) Fuming
• Super Glue fuming- works
great on nonporous surfacesmetals, leather, plastic bags.
• Created when superglue is
placed on cotton and treated
with sodium hydroxide.
• Created when heatingproduces toxic vaporscyanide.
• Fumes and object contained
within an enclosed chamber
for up to 6 hrs.
• Produces white latent print.
Prints can last for years if stored properly!
CHEMICAL METHODS FOR
VISUALIZING LATENT PRINTS
new fingerprinting technology
NINHYDRIN
•
•
•
The most cost effective chemical
development method is Ninhydrin
Ninhydrin is used on paper, cardboard, or
other porous surfaces.
The problem with spraying Ninhydrin
solutions is that, since Ninhydrin reacts with
amino acids, any exposure to your body,
especially to your eyes or lungs, could have
serious results. This potentially dangerous
exposure is minimized by dipping or
painting.
https://www.
youtube.co
m/watch?v=
o89J3dmKC
HM
Iodine fuming
• iodine is a solid crystal that when heated, turns into a vapor without
passing through a liquid phase
– this transformation is called Sublimation.
• Suspect material is placed in an enclosed cabinet with iodine
crystals
• Once heated, vapors fill the chamber and combine with latent print
to make it visible.
• Iodine prints are not permanent and begin to fade once fuming is
stopped.
– NECESSARY TO PHOTOGRAPH IMMEDIATELY
• Can be fixed with 1% solution of starch in water applied by sprayingthis will turn blue and last for several weeks or longer.
https://www.youtube.com/watch?v=SQ9dYQ_OSPg
DFO Chemical Treatment
1,2-Diazafluoren-9-ONE (DFO)
•
•
•
•
Detection of latent fingerprints on
porous or non porous exhibits.
DFO reacts with the amino acids
to produce a light pink colored
product that fluoresces yellow
under blue/ green light.
Process requires spraying with
DFO, rinsing and drying, then
examining with UV light.
Works well for prints that have no
moisture left or can’t be seen with
naked eye.
• DFO (1,8-diazafluotrn-9-one) – newer
chemical than ninhydrin. It is 2.5 times
more sensitive than ninhydrin.
DFO
Prints
Silver Nitrate
•
•
•
•
•
Silver nitrate development is based on the reaction of
soluble silver nitrate with the sodium chloride (salt)
that is present in most latent fingerprints to form silver
chloride.
Exposing the silver chloride to sunlight or an
ultraviolet lamp causes the silver chloride to be
reduced to metallic silver, making the latent prints
visible as black or dark gray traces.
Very old latent fingerprints retain it and can be
developed by silver nitrate. Accordingly, silver nitrate
development may work when iodine fuming and
ninhydrin fail completely.
(Note that failure of these other reagents says nothing
about the age of the latent prints; even prints that are
only hours or days old may respond only to silver
nitrate development.)
Silver Nitrate is destructive, so used as last resort
Other fingerprint chemicals
• Gentian violet (or crystal
violet) – used for developing
latent prints on the adhesive
side of tape. An aqueous
solution of crystal violet is
sprayed directly onto the
adhesive.
• Amido Black – protein dye
stain that can develop faint
bloody fingerprints on porous
and nonporous surfaces.
UNT in partnership with
TEA, Copyright ©. All
rights reserved.
Fingerprint Chemicals
(continued)
• LCV (Leuco Crystal Violet) – a
protein stain spray that can develop
faint or invisible bloody fingerprints
on non-porous surfaces
56
UNT in partnership with
TEA, Copyright ©. All
rights reserved.
PRESERVATION OF DEVELOPED
PRINTS
• Once visualized, it must be permanently preserved for
future comparison and possible use in court as evidence.
• Camera with close-up lens
• Fixed focus to take photographs on 1:1 scale when lens
is held exactly flush against the print surface to avoid
distortion.
• Photograph print’s relative location with other evidential
items.
Permanent Record of Print
•
If on small surface- transport without
destroying the print
•
Protect with cellophane bag
•
If large surface (door, wall, etc) objects
that have been developed with a
powder can best be preserved by
‘”lifting”.
•
Done with broad adhesive tape
•
Fingerprint covered with adhesive side
and pulled up, the powder will be
transferred to the tape.
•
Digital imaging may be used to
enhance contrast, enlarge detail and
compare individual points on prints to
others in question.