Fingerprints
Chapter 14
History
• Alphonse Bertillon - first systematic attempt
at personal indentification
– detailed description of subject (portrait parle´)
• a verbal description of a perpetrator’s physical
characteristics and dress provided by an eyewitness
– full-length and profile photographs
– system of 11 precise body measurements
(anthropometry)
• this rested on the premise that every body had
unique dimensions which remained constant from
age 20 until death
History
• Henry Fauld - first to publish views on the
potential application of fingerprinting to
personal identification
• Francis Galton - published the first book
“Finger Prints” on the subject; also devised
the three types - loops, arches, and whorls
– the book convincingly demonstrated that no
two prints were identical and that prints
remained the same from year to year
History
• Dr. Juan Vuetch - 1891 - devised a workable
classification system that allowed prints to
be filed and retrieved; still widely used in
Spanish-speaking countries.
• Sir Edward Richard Henry - 1897 proposed another classification system that
was adopted by Scotland Yard in 1901 and
is used in most English-speaking countries
in some capacity today.
History
• New York City Civil Service Commission - 1901 first to use fingerprints for personal identification
purposes in the United States
• 1924 - the fingerprint records of the Bureau of
Investigation and Leavenworth were merged to form
the new FBI data base.
• 1999 - the admissibility of fingerprint evidence was
challenged. Judge upheld the admissibility of
fingerprints as scientific evidence and ruled that (1)
human friction ridges are unique and permanent and
(2) human friction ridge skin arrangements are unique
and permanent.
Fundamental Principles of
Fingerprints
First Principle
A fingerprint is an individual
characteristic; no two fingers
have yet been found to possess
identical ridge characteristics
First Principle
• Galton - showed through mathematical
calculations that theoretically there existed a
possibility of 64 billion different
fingerprints
• Also proven by the fact that there have been
millions and millions of prints taken in the
last 90 years and there have never been two
the same
First Principle
• The individuality of a fingerprint is not
determined by its general shape or pattern;
this would classify in the class characteristic
• Ridge characteristics (aka minutiae) - ridge
endings, bifurcations, enclosures, islands,
ridge crossings, short ridges, etc.
• The identity, number, and relative location
of characteristics will impart individuality
to a fingerprint
Second Principle
A fingerprint will remain
unchanged during an
individual’s lifetime
Second Principle
• Fingerprints are a reproduction of friction
skin ridges found on the palm side of the
fingers, thumbs, palms, and soles of the
feet.
• These ridges are designed to provide a
firmer grasp and a resistance to slippage.
Anatomy of Skin
• Layers:
– Epidermis outer layer
– dermis - inner layer
– dermal papillae - boundary between the
epidermis and dermis
• shape of boundary determines the form and pattern
of ridges on the surface of the skin that causes the
fingerprint
– sweat gland - a pore in each skin ridge that
allows for perspiration to be discharged and
deposited on the surface of the skin
Anatomy of Skin
• To alter the fingerprint one would have to
change the dermal papillae layer. A cut of
1-2 mm below the skin surface could
penetrate the dermal papillae layer however
the scar would then become a characteristic
• It is totally impossible to completely
obliterate the entire ridge pattern from a
person
Third Principle
Fingerprints have general ridge
patterns that permit them to be
systematically classified.
Third Principle
• Whorls - 30-35% of the population
– a class of fingerprints that includes ridge patterns that are
generally rounded or circular in shape and have two deltas
• Loops - 60-65% of the population
– a class of fingerprints characterized by ridge lines that enter
from one side of the pattern and curve around to exit from the
same side of the pattern
• Arches - ~5% of the population
– a class of fingerprints characterized by ridge lines that enter
the print from one side and flow out the other side
Whorls
• Whorls - must have at least two deltas and type lines
– Plain whorl - if an imaginary line drawn between the two
deltas touches any one of the spiral ridges; has at least one
ridge that makes a complete circuit
– Central pocket loop - if an imaginary line drawn between the
two deltas does not touch any one of the spiral ridges; has at
least one ridge that makes a complete circuit
– Double Loop - made up of two loops combined into one
fingerprint
– Accidental - contains two or more patterns (not including the
plain arch) or is a pattern not covered by other categories
Plain Whorl
http://www.nist.gov/srd/fing_img.htm
Loops
• Loop - must have one or more ridges entering from
one side of the print, recurving, and exiting from the
same side; must have one delta
– type lines - the pattern area of the loop is surrounded
by two diverging ridges known as type lines
– delta - the ridge point at or nearest the type-line
divergence and located at or directly in front of the
point of divergence
– core - the approximate center of the pattern
– Radial loop - opens toward the thumb
– Ulnar loop - opens toward the little finger
Right Loop
http://www.nist.gov/srd/fing_img.htm
Left Loop
Arches
• Arches - do not contain type lines, deltas, or
cores
– Plain arch - simplest of all fingerprint patterns;
formed by ridges entering from one side of the
print and exiting on the opposite side; ridges
tend to rise in the center of the pattern forming
a wavelike appearance
– Tented arch - similar to the plain arch except
the rise is a sharp upthrust or spike instead of a
smooth rise
Plain Arch
http://www.nist.gov/srd/fing_img.htm
Tented Arch
Classification of Fingerprints
• Primary Classification - part of the original
Henry system and is the first step
– provides that all fingerprints can be initially
classified into 1024 groups
– all fingers are paired up into fractions in this
specific sequence
R-Index R-Ring L-Thumb L-.Middle L-Little
R-Thumb R-Middle R-Little L-Index L-Ring
Classification of Fingerprints
• The whorl pattern is the basis for the determination
• If a whorl is present a number is assigned
–
–
–
–
–
pair 1 = 16
pair 2 = 8
pair 3 = 4
pair 4 = 2
pair 5 = 1
• The total for the numerator and denominator is
summed and 1 is added to both.
• Approximately 25% of the population have 1/1
primary classification. This is a class characteristic!
AFIS
• Automated Fingerprint Identification Systems
– uses automatic scanning devices that convert the
image of a fingerprint into digital minutiae that
contain data showing ridges at their points of
termination (ridge endings) and the branching of
ridges into two ridges (bifurcations).
• Automation allows for less time identifying a
suspect and more time to investigate the
suspect the computer generated.
Methods of Detecting Fingerprints
• Types of fingerprints:
– latent - aka invisible - impressions caused by
the transfer of body perspiration or oils present
on the finger ridges to the surface of an object
– visible - made by fingers touching a surface
after the ridges have been in contact with a
colored material such as blood, paint, grease, or
ink
– plastic - ridge impressions left on a soft
material such as putty, wax, soap, or dust
Methods of Detecting Fingerprints
• How to visualize the latent prints
– Hard and nonabsorbent surfaces - preferably
developed by application of a powder or
treatment with Super Glue
• glass, mirror, tile, and painted wood
– Soft and porous surfaces - treated with one or
more chemicals
• papers, cardboard, and cloth
Powders
• Generally gray and black sufficient for most
– examiner chooses powder that best contrasts the
color of the surface.
• Gray - aluminum metal - applied to dark colors
and mirrors or metal surfaces…because when it is
photographed the surface will be black
• Black - charcoal - applied to light colored surfaces
Chemical Methods
• Iodine fuming - sublimes during heating;
not permanent; fades very quickly; can be
held for a few weeks if sprayed with a
starch solution - print will turn blue
– thought that the fumes combine with fatty oils
and/or the residual water left on a print from
perspiration
Chemical Methods
• Ninhydrin - reacts with amino acids present
in the perspiration; forms a purple-blue print
– sprayed onto the porous surface
– prints develop within an hour or two; weaker
prints may take 24-48 hours; heating the treated
specimen speeds up the visualization
Chemical Methods
• Physical Developer - silver nitrate-based
liquid reagent; final chemical resort
– shown to be very effective on porous articles
that may have been wet at one time
• Specific order for visualizing prints
1) - iodide fuming
2) - ninhydrin
3) - Physical Developer
Chemical Methods
• Super Glue fuming - done on nonporous
surfaces
– metals, electrical tape, leather, plastic bags,
– cyanoacrylate ester - reacts with and visualizes
a latent print
Fluorescent Techniques
• Laser light illuminates the components in perspiration
that naturally fluoresce.
• Fluorescence is the phenomenon that occurs when a
substance absorbs light and reemits the light in
wavelengths longer than the illuminating source.
• Substances that emit light or fluoresce are more
readily seen with the naked eye or through
photography as compared to non-light-emitting
materials.
• The high sensitivity of fluorescence serves as the
underlying principle of many of the new chemical
techniques used to visualize latent prints.
Fluorescence Advancements
• Chemicals that would induce fluorescence
when exposed to laser illumination.
– Ie. Applying zinc chloride after ninhydrin
– ie. Applying rhodamine 6G after super glue
• Alternate Light Source systems - high
intensity light sources have replaced most
lasers; must less expensive; portable
– ie. Quartz halogen, xenon arc, indium arc
Miscellaneous Information
• Chemical treatments of fingerprints do not
interfere with DNA testing.
• Latent Print Preservation
– an initial photograph must be taken
– if item can be removed and preserved as
evidence this is done properly
– if item is too large or permanently attached then
the print is “lifted” with tape and placed on a
card for preservation.
Miscellaneous Information
• Digital imaging - the process by which a picture is converted
into a digital file; the image produced from this digital file is
composed of numerous square electronic dots called pixels
– grayscale - only contains black (0) and white (255); can
manipulate the color by changing the value
– resolution - reveals the degree of detail; 600x800 pixels; the
larger the numbers the closer the image resembles the real
image
• Frequency analysis - frequency Fourier transform (FFT) is
used to identify periodic or repetitive patterns such as lines or
dots that are interfering with the interpretation of the image;
these can be diminished or eliminated to enhance the image