Transcript Fingerprints

Fingerprints
Chapter 14
Criminalistics
History of
Fingerprinting
– Alphonse Bertillon in 1883
• First systematic attempt at personal
identification
– Anthropometry: system of precise body
measurements.
• Included detailed descriptions of the subject
• Believed that dimensions of the human bone system
remained fixed from the age of 20 until death.
• Full-length and profile photographs
• Problems? Accuracy of measurements were disproved by
the William West Case
William Herschel
• Required natives in
India to sign contracts
with the imprint of
their right hand
• Not sure if he noticed
the differences in
prints or was
practicing a Hindu
custom
• Did not publish any
ideas until after Fauld
Henry Fauld (1880)
• Suggested skin ridge
patterns were
important for
identification of
criminals
History of Fingerprinting
• Francis Galton
– 1892: Published Finger Prints
• Described the anatomy of fingerprints and
suggested methods for recording them
• Acknowledged that no two prints are alike
and do not change throughout a lifetime
• Three pattern types
– Loops, Arches, and Whorls
Dr. Juan Vucetich
• Argentinian police
officer
• First to devise a
classification system
for fingerprints
• Although modified,
still widely used in
Spanish-speaking
countries
Sir Edmund Richard Henry
• Proposed another
classification
system in 1897
• Most Englishspeaking countries
use some form of
this system to this
day
Fundamental Principles of
Fingerprints
• First Principle
– A fingerprint is an individual characteristic. No
two fingers have yet been found to possess
identical ridge characteristics
– Ridge Characteristics: The combination of
details in the shapes and positions of ridges in
fingerprints that make each unique; also called
minutiae.
• Examples: bifurcation, enclosures, islands, ridge
endings, short ridges, ridge crossings, deltas
Minutiae:
Names
Visual Appearnce
Double
Bifurcation
Island ridge
(or short ridge)
Spur
(or hook)
Trifurcation
Eye
(enclosure or
island)
Dot (or very
short ridge)
Figure 14-1
Figure 14-2
Fundamental Principles of
Fingerprints
• Second Principle
– A Fingerprint remains unchanged during an
individual’s lifetime
– Formation of fingerprints:
• Developed during fetal development
• Hills (Ridges): raised portions of the
epidermis
• Valleys (Grooves): lowered portions of the
epidermis
• IT IS THE RIDGES THAT ARE INKED
WHEN FINGERPRINTS ARE TAKEN
•
The three layers that
compose skin are epidermis
(outer layer), dermis (inner
layer) and the shape of the
dermal papillae which
determine the form and
pattern of the ridges at the
surface of the skin.
• It is impossible to change one’s fingerprint even
though there have been numerous attempts.
• Serious injury can leave permanent scar. But it
must penetrate 1 to 2 millimeters beneath the
skin’s surface.
– Must damage the dermis
John Dillinger
• Tried to destroy
fingerprints by using
corrosive acid
• Prints taken at the
morgue after his
death were compared
to prints taken from
an earlier arrest
showed that prints
were unchanged and
his efforts useless.
John Dillinger- before acid
John Dillinger prints- after
acid
“Smiling Gus” Winkler
• Famous criminal of
the 1920’s
• Had a strip down
the center of his
fingerprint
surgically removed
• Efforts did not
completely destroy
ridge patterns
Before and After
Fundamental Principles of
Fingerprints
• Third Principle
– Fingerprints have general ridge
patterns that permit them to
systematically classified.
Three Classes of Fingerprints
• Loops, Whorls, and Arches
– Loops: 65% of world’s population
– Whorls: 30-35% of world’s population
– Arches: 5% of world’s population
Loops
Whorls
Arches
Loop Patterns
• One or more
ridges entering
from one side of
the print,
recurving, and
exiting from the
same side
Types of Loop Patterns
• Ulnar Loop: loop opens toward little
finger
• Radial Loop: loop opens toward the
thumb
– Type Lines: pattern area of the loop
surrounded by two diverging ridges
– Delta: the point directly in front of the
diverging ridges—loops MUST have at
least one delta
– Core: the center of pattern
Types of Whorl Patterns
• Four types of patterns
–
–
–
–
Plain Whorl
Central Pocket Loop Whorl
Double Loop Whorl
Accidental Whorl
All whorl patterns must have type lines
and a MINIMUM of two deltas.
Types of Whorl Patterns
• Plain and Central Pocket Loops
– Plain whorl and central pocket loops have
AT LEAST one ridge that makes a
complete circuit
– Ridge may be a spiral, oval, or any variant
of a circle
Types of Whorl Patterns
• Plain Whorl: an imaginary line is drawn
between TWO deltas and the spiral is
crossed
• Central Pocket Loop: spiral is not crossed
when imaginary line is drawn
Types of Whorl Patterns
• Double Loop: has two loops in one
fingerprint
• Accidental Loop: has two or more
patterns or is not classified into any
other category
Types of Whorl Patterns
Figure 14-6
Arch Patterns
• Plain arch: ridges entering one side
of the fingerprint and exiting the
other side
• Tented arch: this pattern rises
sharply in the center
Arch Patterns
Figure 14-7
Classification of Fingerprints
• The original Henry System converted
ridge patterns on all 10 fingers into a
series of numbers and letters
arranged in the form of a fraction.
– Problem: It could only classify
fingerprints up to 100,000 sets of prints
so as collections grew, it became
necessary to expand the capacity of the
classification system.
FBI System
• In the US, the FBI expanded the
classification capacity and these
modifications are collectively known
as the FBI System.
• Using the FBI System, all fingerprint
cards can be divided into 1,024
groups.
How the FBI System Works
• The following sequence can be used to
classify fingerprints:
R. Index R. Ring
L. Thumb L. Middle L. Little
R. Thumb + R. Middle + R. Little + L. Index + L. Ring
16
8
4
2
+
0
Zeros are assigned for loops and arches
Fraction gives individualized result for each person
1
1
Whorl
Values
• The presence or absence of the whorl
pattern is the basis for determination
of the primary classification.
• If a whorl pattern is found on any
finger of the first pair, it is assigned
a value of 16.
• On the second pair, a value of 8.
•
•
•
•
On the third pair, a value of 4.
On the fourth pair, a value of 2.
On the last pair, a value of 1.
Any finger with an arch or loop
patterns is assigned a value of 0.
• Once all values are obtained, then 1/1 is
added to the numerator and denominator.
• A fingerprint classification system cannot
identify an individual, rather it provides a
number of candidates that have similarities
with the known set of prints.
• The identification must always be made by
a final visual comparison of the suspects
print’s and the file print’s ridge
characteristics.
Problems with FBI System
• 25% of population falls into the 1/1
category
• Only useful when all 10 prints are
available
• Cumbersome and Time Consuming to
look through cards
• Often only one or two prints found at
a crime scene
AFIS
• Automated Fingerprint Identification
System
• Computer-scans and digitally encodes
fingerprints based on minutiae of
ridge endings and bifurications
• List of prints is generated then a
fingerprint examiner confirms match
Benefits of AFIS
• Computer can make thousands of
accurate fingerprint comparisons in a
second
• Can filter out imperfections in latent
prints found at a crime scene
• Suspect lists are generated faster
and investigators can spend more
time focusing on suspects
A Typical AFIS Matching Screen
IAFIS
• Integrated Automated Fingerprint
System
– Largest AFIS in the United States
– Contains nearly 50 million fingerprint
records
• What is included in IAFIS:
• Not only fingerprints, but corresponding criminal
histories; mug shots; scars and tattoo photos; physical
characteristics like height, weight, and hair and eye
color; and aliases.
• The system also includes civil fingerprints, mostly of
individuals who have served or are serving in the U.S.
military or have been or are employed by the federal
government.
• The fingerprints and criminal history information are
submitted voluntarily by state, local, and federal law
enforcement agencies.
Types of Crime Scene Prints
• Three Types:
– Visible Prints
– Plastic Prints
– Latent (Invisible) Prints
Visible Prints
• Can be seen with the
naked eye
• Made by fingers touching
a surface after ridges
have been in contact with
a colored material such as
blood, paint, grease, ink,
etc.
Plastic Prints
• Can be seen with the naked eye
• Made by ridge impressions left on a
soft material such as putty, wax,
soap, dust, wet paint surfaces, etc.
Latent Prints
• Cannot be seen with the naked eye
• Made by impressions caused by
transfer of body perspiration or oils
present on finger ridges to the
surface of an object
Easiest surface to lift
fingerprints:
• Hard, nonabsorbent surfaces (glass,
mirrors, tile, painted wood): Powders
or SuperGlue Fuming
Fingerprint Powders
• Applied with a camel’s hair or fiberglass
brush
• Color of powder (usually gray or black)
are chosen to contrast with surface color
• Powder adheres to oils and perspiration
left by ridges
• Print can be lifted off the surface and
preserved
• Magna Brush
– Can spread
magnetic-sensitive
powder to locate
latent prints
– Does not have any
bristles to come in
contact with
surface, meaning
less chance of
destroying or
damaging a print
Ninhydrin
• Chemical used to develop prints on porous material
such as paper
• Applied by dipping the object or spraying it with
ninhydrin
• Safety: Do not inhale or get on your skin
• Reacts with amino acids in perspiration
• Developed prints appear purple-blue in color
– Prints appear within an hour or two and fully
developed in 24-48 hours
Latent Prints recovered on paper with Ninhydrin
SuperGlue Fuming
• Used on nonporous surfaces such as metal, electrical
tape, leather, and plastic bags
• Application: Evidence is placed in a fuming chamber
and the cyanoacrylate is heated and covers the object
• Safety: Do not inhale or get on your skin, irritant to
mucus membrane.
• Reacts with amino acids
• Produces a white latent print
Flashlight battery exposed to SuperGlue Fuming
Physical Developer (Silver
Nitrate)
• Useful for detecting prints that cannot be found
by other methods or on objects that have been
wet at one time. Also on wood or styrofoam.
• Applied by dipping or spraying object with Silver
Nitrate.
• Safety: Wear gloves and avoid contact with skin.
• Reaction: Chloride from salt in perspiration on the
print combines with silver nitrate to form silver
chloride.
• Print turns black or reddish brown under a UV
light
– ***Application of Physical Developer washes away any protein that may
be present and MUST be used last
Iodine Fuming
• Used to detect prints on paper, cardboard and unpainted
surfaces (non-pourous)
• Iodine is a solid crystal that, when heated, is transformed
into a gas through sublimation and reveals a latent print.
• Safety: Toxic to inhale or ingest
• Reaction: Iodine combines with carbohydrates in the print
• A brownish print forms but prints are not permanent and
must be photographed immediately or fixed with starch
solution, which can last about 1 month
Alternate Light Source
• Works because perspiration
fluoresces under different
wavelengths of light
• Can adjust the wavelength of
light to be aimed through a fiber
optic cable
• More commercially available than
laser light setups
Alternative Light Source being used to detect latent
prints
Preservation of Prints
• Once a latent print has been
visualized it must be permanently
preserved for future comparison and
possible use in court as evidence.
• Photograph must be taken before and
after further attempts to preserve
the fingerprint.
Two Procedures to Follow:
• If object is small enough to be
transported without destroying the
print, it should be preserved in its
entirety.
• Cellophane should cover the print to
protect from damage
– Prints on large immovable objects that have
been developed with a powder can be best
preserved by “lifting”.
• The most popular type of lifter is a broad
adhesive tape similar to clear adhesive tape.
• When the powdered surface is covered with
the adhesive side of the tape and pulled up,
the powder is transferred on the tape.
• The tape is then placed on a properly labeled
card that provides a good background
contrast with the powder.
Digital Imaging
• When fingerprints are lifted from a
crime scene, they are usually not in
perfect condition.
• Using digital imaging, fingerprints can
now be enhanced for the most
accurate and comprehensive analysis.
Digital Imaging
• The process by which a picture is
converted into a digital file
• Although digital imaging is
undoubtedly an effective tool for
enhancing and analyzing images, it is
only as useful as the images it has to
work with.