Transcript Fingerprinting - Warren County Schools

Fingerprinting
Bertillon Method of ID
• A French police expert, Alphonse Bertillon,
relied on a description of the subject, with
precise body measurements.
• Skeletons were thought to be so diverse
that no two people would have the same
measurements.
• This system of ID became known as the
Bertillon system and was practiced for over
20 years.
History of Fingerprinting
• Evidence exists that the Chinese used
the fingerprint to sign legal documents
as far back as three thousand years
ago!
• However, it is not known whether the
practice was for ceremonial purposes
or for personal identification.
History of Fingerprinting
• It wasn’t until 1880 that Henry Fauld
suggested that ridge patterns may be used
for important identification of criminals.
• He noted that a thief left fingerprints at the
crime scene on a white-washed wall. When
compared with the suspect’s fingerprints,
there were obvious differences.
• Finding the person who had fingerprints that
matched resulted in the person confessing
to the crime.
History of Fingerprinting
• Francis Galton was the first person to
print a textbook on the subject of
fingerprinting. (Finger Prints, 1892)
• He was the person who proposed
three basic patterns of fingerprints:
• 1) loops
• 2) whorls
• 3) arches
History of Fingerprinting
• In the US, the first systematic and official
use of fingerprints for personal identification
was used by the New York City Civil Service
Commission in 1901.
• In 1924, the fingerprint databases of the FBI
and Leavenworth prison were merged to
form the nucleus of the FBI records.
• The FBI currently has the largest database
of fingerprint records in the world.
AFIS
• The FBI database has over 50 million
fingerprint records. State AFIS records
were linked to the FBI in 1999.
• Smaller, independent AFIS systems, like
those of local police, often are not
compatible with the FBI database due to
software issues!
• AFIS searches for several minutiae
characteristics. Correlation between the
location and minutiae present are
considered.
AFIS
• AFIS is not a replacement for an actual
person…
• CSI myth- the computer does not
narrow it down to 1 match. An actual
person must search through possible
matches to choose the best choice.
Principles of Fingerprints
• First principle: A fingerprint is an individual
characteristic; No two fingers have yet been
found to possess identical ridge
characteristics.
• This principle is supported by theoretical
calculations.
• The individuality is determined by a
fingerprint’s ridge characteristics. The
identity number and the location are what
are unique.
Identification Criteria
• A given fingerprint may have as many as
150 individual ridge characteristics.
• However, there are usually only partial
prints found at crime scenes.
• There has been much debate about how
many ridges are necessary to declare an
individual match.
• The consensus is that there is no minimum
number because there has not been a
comprehensive statistical study done to
prove how many ridges are necessary to be
considered a match.
Principles of Fingerprinting
• Second principle: A finger print will remain
unchanged during an individual’s lifetime.
• Fingerprints are a reproduction of friction
skin ridges found on palms to provide us
with a firmer grasp and resistance to
slippage.
• They resemble a series of lines that
correspond to hills (ridges) with valleys
(grooves) in between them.
Layers of the Skin
• The outer portion of
skin is called the
epidermis.
• The inner portion of
the skin is called
the dermis.
• The layer in
between is made
up of dermal
papillae, which
determine the ridge
characteristics.
Dermal Papillae
• Once the dermal papillae develop in
the fetus, the ridge patterns will remain
unchanged throughout life except to
become larger due to growth.
Latent Prints
• Prints that are invisible to the eye are
commonly referred to as latent prints.
• These prints are formed by
perspiration and oils that is discharged
and deposited on the surface of the
skin.
• Once the finger touches a surface, the
ridge patterns are transferred to that
surface, leaving behind a fingerprint.
Is it possible to destroy
fingerprints?
• Many criminals have tried…
• If an injury penetrates the skin deeply
enough (1-2 mm), a permanent scar may
form.
• By intentionally scarring fingerprints, the
result would be to leave further identifying
evidence. Now the scars make the prints
even more unique!!!
• It is impossible to obliterate all ridge
characteristics!!!
Principles of Fingerprinting
• Third principle: Fingerprints have
general ridge patterns that permit them
to be systematically classified.
• 60-65% of the population have loops
• 30-35% have whorls
• 5% have arches
Ridge Characteristics
Loops
• Defined: one or more ridges entering
from one side of the print and exiting
the same side
• Ulnar loop- the loop enters and exits
towards the little finger
• Radial loop- the loop enters and exits
towards the thumb
• All loops must have at least 1 delta. A
delta is an area of divergence, like the
term for a delta in the water sense.
Loop
Characteristics
Whorls
• All whorls have type lines and
at least 2 deltas.
• 4 distinct groups:
• 1 and 2) plain and central
pocket loop- at least 1 ridge
makes a complete circuit (any
form of a circle)
• If an imaginary line drawn
between the two deltas
touches any one of the spiral
ridges, it is a plain whorl. If
not, it is a central pocket loop.
Whorls
• 3) Double loop- two
loop combine into 1
fingerprint
• 4) Accidental whorl- either
contains 2 or more patterns
(not including the plain
arch) or Is a pattern not
covered by other categories
Arches
• The least common
of the three groups!
• 2 types:
• 1) Plain- Ridges
entering one side
and exiting the
other side, usually
with a rise in the
center
• 2) Tented- similar to
a plain arch, except
instead of gradually
rising, it rises
sharply in the
center
• Arches DO NOT
have deltas, type
lines or cores!
Plain vs Tented Arch
Types of Prints
• 1) Visible prints- prints • 2) Plastic Printsthat show ridges and
ridge impressions
patterns after coming in
are left in a soft
contact with a colored
material like putty,
material, like blood, ink,
butter, wax, etc.
etc.
• These prints are
• No specialty equipment
photographed, not
is necessary to detect the
lifted.
print. They are often
photographed.
Types of prints
• 3) Latent printsinvisible prints,
cannot be seen with
the naked eye
• Must be developed
by 1 or more
methods to be
visible.
Locating Latent Prints
• Recent advances in
• It works by reflecting
fingerprint technology led UV light back to the
to the development of a
viewer from the print
devise called RUVIS.
so it is differentiated
from its background.
• This reflected ultraviolet
imaging system can
• This works because
illuminate prints without
certain components
the use of chemicals and
of perspiration
powders.
fluoresce.
Detecting Latent Prints
• Chemical methods• Certain chemicals or
chemical
combinations can
induce fluorescence
that is visible when
exposed to a laser.
• Iodine fumingiodine sublimates
from solid to a purple
gas. The iodine is
heated in the
presence of the
evidence.
• The iodine fumes
“stick” to the
constituents of the
print making it visible.
Iodine Fuming
• Fuming with iodine
is an older methodbecause the prints
fade quickly after
fuming is stopped.
• It can be “fixed” by
spraying with a
starch solution to
turn the print
blue/purple.
Ninhydrin
• This chemical
developer reacts with
amino acids present
in trace amounts in
perspiration to create
a blue/purple color.
• Prints develop within
an hour to 2 hours.
• Weaker prints may
take 24-48 hours to
develop.
• The ninhydrin
solution is prepared
by mixing the
powder with acetone
or ether to dissolve
and spraying on the
surface.
Physical Developer
• Physical developers • Chemical treatments
are a chemical
like those previously
mixture using silver
described were the
nitrate to visualize
most popular method
latent prints.
for detecting latent
prints on porous
• This method works
surfaces like paper
when other
and cardboard, but
methods fail…like
now a new method is
the ninhydrin or
being used.
iodine method.
Cyanoacrylate Fuming
• Superglue can be
heated to produce
fumes.
• This is done inside a
chamber to produce a
white coating on a
latent print.
• The process usually
takes several hours.
• Now, superglue
fuming wands are
available to use at
the scene.
• Rhodamine dye
can be added to
create a
fluorescence effect.