Transcript finger prints - cloudfront.net

Chapter 4: Fingerprints
History
• First fingerprints were discovered in
clay pottery during the T’ang Dynasty
• Dactyloscopy: study of fingerprints
2
History
• Alphonse Bertillion
– First systematic attempt at personal
identification
Bertillion system
– Relied on a detailed description of the
subject
– Combined with full length and profile
photographs
– System of precise body measurements
called anthropometry
3
History
• Francis Galton
– 1892
– Classic textbook finger prints
• At Galton’s insistence
– British government adopted fingerprinting
– Supplement to the bertillion system.
• Next step
– Creation of classification systems
– Capable of filing many thousands of prints
– Logical and searchable sequence.
4
WHY FINGERPRINTS?
• The most positive means for
identifying people.
• Because no two fingers with
identical ridge characteristics
• Fingerprints form on a person
before birth and remain
unchanged until the body
decomposes after death.
Every fingerprint is unique!
WHAT IS A FINGERPRINT?
A fingerprint is a pattern comprised
of ridges and valleys.
A Ridge – is a high.
A Valley – is a depression or low.
Friction ridges are also found on our
palms, feet and toes.
Ridge
Valley
Fingerprint Principles
• Individual characteristic
–Because no two fingers with
identical ridge characteristics
• Remains unchanged during an
individual’s lifetime
• General ridge patterns that permit
systematic classification
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Anatomy of Fingerprints
• Epidermis
– Outer layer of the skin
• Dermis
– Inner layer of the skin
• Dermal papillae
– Layer of cells between
the epidermis and
dermis
– Responsible for
determining the form
and pattern of the
ridges on the surface
of the skin
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Anatomy of fingerprints
• Dermal papillae
develop in the
human fetus @ 3
months
• Enlarge during
growth
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Anatomy of fingerprints
• Finger touches a surface
–Perspiration
–Oils from hairy portions of the
body
–Transferred onto surface
• Leaves fingerprint
11
Fingerprint patterns
• All fingerprints
– divided into three classes
– Loops
– Arches
– whorls
L.A.W.
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Loops
• A loop must have one or more ridges
entering from one side of the print, recurving, and exiting from the same side.
– If the loop opens toward the little
finger, it is called an ulnar loop.
– If the loop opens toward the thumb, it
is called a radial loop.
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Loops
Figure4.3 Loop pattern.
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Loops
• Must have one delta
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Whorls
16
Whorls
• Divided into four groups
– Plain
– Central pocket loop
– Double loop
– Accidental
• All have a minimum of two deltas
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Whorls
• Plain whorl and central pocket loop have at
least one ridge that makes a complete
circuit
• Double loop: two loops combined into one
fingerprint
• Accidental
– Two or more patterns
– Or pattern not covered by the other
categories
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Arches
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Arches
• Least common of general
patterns
– Plain arches
– Tented arches
– Arches do not have deltas,
or cores
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Plain Arches
•
•
•
•
Ridges entering from one side of the print
Rising and falling
Exiting on the opposite side
Like a wave
21
Tented Arches
• Sharp up-thrust or
spike
• The ridges meet at
an angle that is less
than 90 degrees
22
Questions???
How are fingerprints compared?
A. Fingerprints are compared by noting the
ridge characteristics on two prints to
determine whether or not they match.
B. An identification is established when a
number of these characteristics occupy
the same relative position on the two
prints.
Fingerprints and a fingerprint classification schema involving six categories:
(a) arch, (b) tented arch, (c) right loop, (d) left loop, (e) whorl, and
(f) double loop. Critical points in a fingerprint,
called core and delta, are marked as squares and triangles.
FINGERPRINT IDENTIFICATION
RIDGE CHARACTERISTICS (Minutiae)
COMMON
Ending Ridge
OCCASIONAL
RARE
Ridge Characteristics
Use these characteristics as points of identification when comparing fingerprint
samples. The more points you can find in common, the better the match!
RIDGE CHARACTERISTICS MAGNIFIED
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1
10
2
9
3
8
4
5
7
Points 1, 2, 4, 5 are Ending Ridges
Points 8, 10, 11 are Bifurcations
Point 7 Short Ridge
6
Points 3 and 9 are Dots
Point 6 is an Enclosure
(ISLAND)
Review of fingerprint types
Arches
Arches are the simplest type of fingerprints that are formed
by ridges that enter on one side of the print and exit on the
other. No deltas are present.
Spike
or
“tent”
Plain Arch
Ridges enter on one side and
exit on the other side.
Tented Arches
Similar to the plain arch,
but has a spike in the center.
Loops
Loops must have one delta and one or more ridges that enter and
leave on the same side. These patterns are named for their
positions related to the radius and ulna bones.
Ulnar Loop (Right
Thumb)
Loop opens toward
right or the ulna bone.
De
lta
Radial Loop (Right
Thumb)
Loop opens toward the
left or the radial bone.
NOTE: On the left hand, a loop that opens to the left would be an ulnar
loop, while one that opens to the right would be a radial loop.
Whorls
Whorls have at least one ridge that makes (or tends to make) a
complete circuit. They also have at least two deltas. If a print has
more than two deltas, it is most likely an accidental.
Plain
Whorl
Central
Pocket
Whorl
Draw a line between the two deltas in the plain and central pocket
whorls. If some of the curved ridges touch the line, it is a plain
whorl. If none of the center core touches the line, it is a central
pocket whorl.
Whorls – Part 2
Double Loop Whorl
Accidental Whorl
Delta
Delta
Double loop whorls are
made up of any two loops
combined into one print.
Accidental whorls contain two
or
more
patterns
(not
including the plain arch), or
does not clearly fall under any
of the other categories.
Identify each fingerprint pattern.
Right
Hand
Left
Hand
Right
Presenting Fingerprints as Evidence
• No legal requirements on the number of
points but generally the courts will accept 8 to
12 points of similarity as sufficient proof.
• Fingerprints do not lie but human error might
account to wrongful convictions.
Types of Prints
Visible & Latent Prints
39
Latent Prints
• Invisible fingerprints
• Finger touches a surface
• Body perspiration and/or oils present
• Transferred to that surface
• Leaves impression
40
Visible Prints
• Fingers touch a surface after contact with a
colored material such as blood, paint, grease,
or ink
• Plastic prints: left on a soft material, such as
putty, wax, soap, or dust
• Little problem to the investigator
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Visualizing Latent Prints
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Detecting Prints
• Hard nonabsorbent surfaces
– Glass, mirror, tile, painted wood
– Developed by the application of a
powder
– Can be lifted by clear tape & examined
• Porous surfaces
– Papers, cardboard, and cloth,
styrofoam, leather
– Require treatment with a chemical
43
Ninhydrin
• Reacts with amino acids left by
finger
• Produces a orange /purple color
(Ruhemann’s purple)
• Commonly used with paper and
porous surfaces
44
Iodine Fuming
• Heat iodine crystals (produces iodine
vapors)
• Combine with latent prints (react w/ oils on
finger) to make them visible
– Iodine prints are not permanent
– Will fade
– Must photograph the prints immediately
– Works best on porous paper.
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Silver nitrate
• Reacts with the salt left from
sweat in a dried print .
• AgNO3 + NaCl
AgCl
*converts to dark Ag2O
• Turns prints brownish-purple
Super Glue®
• Most widely used method to develop latent
prints
• Best used on nonporous surfaces such as
metals, glass, adhesive tapes and plastic.
• Leaves a white, permanent impression
• can be treated with powders or
fluorescent dyes to create a sharper
contrast.
• 98 to 99 percent cyanoacrylate ester
Super Glue fuming
– Fuming chamber (for up to six hours)
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•
•
•
•
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Reflected UV Imaging System
RUlVIS
No chemicals or powder
Locate With light source
investigator develops the print in
the most appropriate fashion
Powders
• Powders, available in a variety of
colors, can be applied with a brush
or magnetic wand, and adhere to
perspiration and/or body oils of the
print.
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Other methods
• Photograph
Digital Imaging- AFIS
• Digital image: of fingers are pressed against a
glass plate and scanned to a screen.
** can be enhanced,
compared and sent to
AFIS within minutes.
AFIS can compare hundreds of thousands of
prints in less than a second.
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Digital Imagining: IAFIS
• Replaced tradition method of fingerprinting.
• Contains more than 55 million computerized
fingerprint records of known criminals.
• Live Scan electronic fingerprints devices
transmit prints @ the time of arrest or booking
to a central IAFIS database to provide
immediate positive identification, check for
with any suspect latent prints on file, and
provide criminal history.