Fingerprinting
Physical Evidence
 Wherever he steps, whatever he touches, whatever
he leaves—even unconsciously—will serve as a silent
witness against him. Not only his fingerprints and his
shoeprints, but also his hair, the fibers from his clothes,
the glass he breaks, the tool mark he leaves, the paint
he scratches, the blood or semen he deposits or
collects—all of these and more bear mute witness
against him. This is evidence that does not forget. It is
not confused by the excitement of the moment. It is
factual evidence. Physical evidence cannot be
wrong; it cannot perjure itself; it cannot be wholly
absent. Only in its interpretation can there be error.
Only human failure to find, study, and understand it
can diminish its value.
 Paul L. Kirk, Crime Investigation
Fingerprinting
 First form of personal identification system
developed by French police expert Alphonse
Bertillon in 1883
 Bertillon System aka Anthropometry:
 Full length and profile photographs
 Precise body measurements
 Detailed description of the person of interest (portrait
parle)
 Based on premise that dimension of the human
bone system remained fixed from age 20 until
death
Body Measurements
 11 routine measurements, including height, reach, width of
head, length of left foot, wrist circumference, etc.
 Early 1900s: fingerprinting as standard police practice
evolved
 Scot Henry Fauld, in 1880, published a paper about using
fingerprinting for personal identification
 Francis Galton, 1892, Finger Prints
 Loops, arches, and whorls
 An individual’s prints remained unchanged over lifetime
 Insisted British government adopt his system to supplement
Bertillon system
Fingerprinting technology
 Move away from Bertillon system to Fingerprinting
 1903, William West and Bertillon doppelganger Will West at Fort
Leavenworth prison
 1901, NYC Civil Service Commission adopted fingerprinting
 1904 St. Louis World’s Fair: American police officials trained in
fingerprint identification technology by Scotland Yard
 Fingerprinting began to be used in earnest in most US cities
 1924, Bureau of Investigation and Ft. Leavenworth fingerprint
records combined to become FBI fingerprint database
Challenges to Fingerprinting
 1999: United v Byron C. Mitchell in PA
 Defense disputed claim that fingerprints are unique
and distinguishable.
 Four day trial, judge upheld Daubert ruling that
fingerprints are
 admissible as scientific evidence
 human friction ridges are unique and permanent
 human friction ridge skin arrangements are unique
and permanent
Fingerprint Principles
 Fingerprints are a reproduction of friction skin ridges found
on the palm side of the fingers and thumbs.
 The basic principles underlying the use of fingerprints in
criminal investigations are that:
1.
A fingerprint is an individual characteristic because no two
fingers have yet been found to possess identical ridge
characteristics (minutiae);

There are as many as 150 minutiae on the average finger

The identity, number, and relative location of these
minutiae impart individuality
Galton’s calculation
 1 in 1 x 1060, i.e. 64 billion possible different
fingerprint patterns
 In the past 100 years, no two set of fingerprints
have been found to be identical
 Fingerprints are individualized by its ridge
characteristics (aka minutiae)
 Ridge endings
 Bifurcations
 Enclosures
 Lakes
 Ridge dots
Fingerprint ridge characteristics.
 8-16 matches must be made between fingerprints to be
considered from the same individual
 1995: Ne’urim Declaration: no set number of matching
characteristics can be defined, must be based on experience
and knowledge of the expert
A fingerprint exhibit illustrating the matching
ridge characteristics between the crimescene print and an inked impression of one
of the suspect’s fingers.
2nd Principle: Unchanged
2. A fingerprint will remain unchanged during an individual’s lifetime
 Friction skin ridges (palm side of fingers and thumbs, and on palms
and soles of feet)
 Ridges correspond to ridges and grooves (hills and valleys)
 Epidermis (outer layer of skin)
 Dermis (inner layer of skin)
 Dermal Papillae (boundary between dermis and epidermis)
determine form and pattern of ridges and grooves
 Sweat pores: discharge perspiration, oil transmission,
Once the dermal papillae
develop in the human
fetus, the ridge patterns
will remain unchanged
throughout life except to
enlarge during growth.
Final Dermal Surface
Epidermis
Papillae in double
row arrangement
Groove
Furrow
Principle Two
 Once the finger touches a surface, perspiration,
along with oils that may have been picked up by
touching the hairy portions of the body, is
transferred onto that surface, leaving the finger’s
ridge pattern (a fingerprint). Pints deposited in
this manner are invisible to the eye and are
commonly referred to a latent fingerprints.
Cross-section of human skin.
Can Fingerprints be
Destroyed or Removed?
• Typically, no. A minor injury (scrape, scratch
or even burn) won't affect the structure of the
ridges in your fingerprints -- new skin reforms in
its original pattern as it grows over the wound.
• But each ridge is also connected to the inner
skin by small projections called papillae. If
these papillae are damaged, the ridges are
wiped out and the fingerprint destroyed.
www.science.howstuffworks.com/fingerprinting
Can Fingerprints be
Destroyed or Removed?
• Chicago bank robber John Dillinger reportedly
burned his fingertips with acid in the 1930s.
• With new technology and fingerprint scanning
security, law enforcement officials worry that wouldbe criminals might try to steal entire fingers for the
prints.
• Robbers in Malaysia cut off a man's fingers so they
could steal his Mercedes.
• Companies that make biometrics security
equipment realize the potential dangers of this
system, and are now creating scanners that
detect blood flow to make sure the finger is still
alive.
www.science.howstuffworks.com/fingerprinting
3rd Principle: General
patterns
3. Fingerprints have general ridge patterns that permit them to be
systematically classified into three groups: L.A.W.
 Loop: ridge lines enter from one side of the pattern and curve around to
exit from the same side of the pattern




60-65%
Ulnar loop: open towards little finger
Radial loop: open towards thumb
Delta: ridge point closest to area of divergence. All Loops have one delta
 Whorl: ridge patterns that are generally rounded or circular in shape and
have at least two deltas
 30-35%
 Four groups: Plain, central pocket loop, double loop, and accidental
 Arch: ridge lines that enter the print from one side and flow out the other
side
 ~5%
 Plain and tented
Loop pattern.
All loops must have one delta, which is the ridge
point at or directly in front of the point where two
ridge lines (type lines) diverge.
Whorl patterns.
 A plain whorl and a central pocket loop have at least one ridge that
makes a complete circuit.
 If an imaginary line drawn between the two deltas within these patterns
touches any of the circular ridges, the pattern is a plain whorl. If no such
ridge is touched, the pattern is a central pocket loop.
 The double loop is made up of two loops combined.
 An accidental either contains two or more patterns, or is a pattern
not covered by the other categories. Hence, an accidental may
consist of a combination loop and plain whorl or loop and tented
arch.
Arch patterns.
 The plain arch is formed by ridges entering from one side of the
print, rising and falling, and exiting on the opposite side (like a
wave).
 The tented arch is similar to the plain arch except that instead
of rising smoothly at the center, there is a sharp upthrust or
spike, or the ridges meet at an angle that is less than 90
degrees.
 Arches do not have type lines, deltas, or cores.
Bifurcation
Ridge ending
Short ridge
Ridge crossing
Enclosure
ACE-V methodology
Analysis
Comparison
Evaluate
Verification
• Examination of Unknown
• Compare Unknown to Known Prints
• Consider prints in totality
• Compare entire hand at once
• Second analyst reviews hypothesis formed
during ACE process
ACE-V: Comparison
Must compare the questioned print at (3) levels.
 Level 1 encompasses the general ridge flow
and pattern configuration.
 Level 2 includes locating and comparing ridge
characteristics or minutiae.
 Level 3 includes the examination and location
of ridge pores, breaks, creases, scars, and
other permanent minutiae.
Definitions
 Visible prints: prints made by fingers touching a
surface after the ridges have been in contact
with colored material such as blood, paint,
grease or ink.
 Plastic prints: ridge impressions left on a soft
material such as putty, wax, soap, or dust
 Latent (invisible) prints: impressions caused by the
transfer of body perspiration or oils present on
finger ridges to the surface of an object
For left hand
Henry Classification System
 Englishman Sir Edward Richard Henry system
proposed in 1897 and adopted by Scotland Yard
in 1901
 Converted ridge patterns on all ten fingers into a
series of letters and numbers arranged in the form
of a fraction.
 Modified, as original system only could be used for
up to 100,000 unique fingerprints
Primary Classification
 10 finger Identification System is part of the Henry
System
 Still part of initial FBI system
 Used to give a suspect candidate pool. Example:
R. Index
R. Ring
L. Thumb
L. Middle
L. Little
R. Thumb
R. Middle
R. Little
L. Index
L. Ring
16
0
+
+
0
8
+
+
0
0
+
+
0
0
+
+
0
0
+ 1 = 17
+ 1 = 8
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, an 8; on the third pair, a 4; on the second
pair, a 2; and on the last pair, a 1.
 Any finger having a loop or arch is assigned a 0.
 After values for all 10 fingers are obtained, they
are totaled, and a 1 is added to both the
numerator and denominator.
 The fraction thus obtained is the primary
classification.
Primary Classification
 A fingerprint classification system
cannot in itself unequivocally identify
an individual; it will merely provide the
fingerprint examiner with a number of
candidates, all of whom have an
indistinguishable set of prints in the
system’s file.
Automated Systems
 Computer approach replaced manual
approach ca. 1970.
 AFIS: Automated Fingerprint
Identification Systems
 In AFIS, computers scan and digitally
encode fingerprints for rapid
fingerprinting archive searches
 Data encoded so that the ridges at points of
termination and branching of ridges into two
ridges are made into digital minutiae
Importance of AFIS
 Speed
 Larger, less cumbersome catalogue
 Ability to identify single, latent prints more readily in
no-suspect cases
 Able to digitally enhance and filter out
imperfections on latent prints
 However, some latent prints are not really suited for
searching using a computer database
 Still require manual printing of the suspect and visual
comparison to the prints lifted from the crime scene
How to identify print
locations
Where would you look for prints
when first processing a crime
scene?
Processing Fingerprints
 Hard, non-absorbent surfaces
 Develop with powder, SuperGlue, etc
 Soft, porous surfaces
 Involve chemicals, e.g. ninhydrin
 Reflected UV Imaging System (RUVIS)
 Locate prints on most non absorbent surfaces without the aid of
chemical or powder treatments
 Powder: grey (aluminum) or black (carbon), whichever color
is best for visualizing prints on the surface material
 Also magnetic or fluorescent powders
Iodine Fuming
 Help visualize latent prints
 Iodine, when heated, sublimates (i.e. phase
changes from solid to vapor without becoming a
liquid)
 After heating, the iodine vapor will chemically
react with compounds in the latent print and
make it visible
 Not a permanent visualization process unless fixed
 Fixation of print with 1% aqueous starch solution
 Print will turn blue and will be “fixed” for several
weeks to several months
Ninhydrin Processing
 Chemically reacts with amino acids (in
perspiration) to form a purple-blue color
 Sprayed onto a porous surface using an
aerosoloizer
 Prints start to develop within an hour, but may
take up to 24-48 hours
 Process can be accelerated if heat is used (80100 C)
Ninhydrin Test:
Ruhemann’s purple =
Positive for Amino Acids
1,2,3-triketo-hydrindene hydrate
Physical developer
 Silver nitrate based liquid reagent
 Newer technique gaining in popularity
 Particularly on porous materials that may
have been wet at one time
Treatment Order on Porous
Surfaces
 Iodine fuming
 Ninhydrin visualization
 Physical Developer
SuperGlue Fuming
 On non porous surfaces such as metals, electrical
tape, leather, and plastic pages or bags
 98-99% Cyanoacrylate ester with sodium
hydroxide
 Chemical interacts with and visualizes latent print
 Develop within six hours as fumes from glue
adhere to print
 Print will appear white
Argon Ion Laser
 Certain compounds in fingerprints (in
perspiration) will exhibit natural fluorescence with
excited with laser light
 Easier to see with naked eye or photography
 Ar-ion laser: blue green light
 Need to use laser safety goggles to filter out light
 Also can use secondary fluorescent dyes – i.e.
chemically-induced fluorescence: Rhodamine
6G or zinc chloride
Rules for visible fingerprints
Fingerprints found in conjunction
with fluids (e.g. DNA (blood, saliva,
etc) should be transported to the
lab for processing, with no
visualization methods being used
at the crime scene
Preservation of Prints
 Preserve print visually
 Photography:
 fixed focus of the print
 general location
 Preserve print physically
 If small, transport entire area that include print
 If large, and on immovable objects, “lift” the print
 Lift using something like scotch tape
 Adhere tape to a cardboard-type backing that
provides a background contrast with the powder
Digital Imaging
 Print processed digitally (pixellation)
 on grey-scale vs. color scale
 0 (black) to 255 (white)
 Resolution: degree of detail that can be
seen in an image. Larger the number of
pixels, the better the resolution
 FFT: frequency Fourier Transform analyzes
the frequency of the patterns that may
be interfering with the digital processing
and can be used to enhance the image
Houston Cold Case
 Diane Maxwell Jackson, abducted, raped,
strangled, and stabbed to death on December
14, 1969
 No suspects initially identified
 Brother campaigned to have case reopened ca.
1989
 Houston PD and TX Dept. of Public Safety: no
possible matches
 July 2003: 20 possible matches with IAFIS
James Ray Davis number one
candidate for a match
Previous crimes, but they needed a
confession in order to prosecute
him.
Why did they need his confession?
Randy Scott: Sept. 11, 2001
Basics on How to Compare
Fingerprints
 https://www.youtube.com/watch?v=IrpTqKkgyg
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