Transcript Fingerprints

Fingerprints
Summary
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What are fingerprints?
How are fingerprints analyzed?
How are fingerprints collected?
Fingerprints
What are fingerprints?
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Friction
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Found on
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Composed of
(hills) and
(furrows)
Black = Ridges
White = Valleys
Fingerprints
What are fingerprints?
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Develop in
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Pattern based on
detail somewhat
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Identical twins
have
fingerprints
,
Fingerprints
History of Fingerprints
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Long history of fingerprints as signature
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Criminal identification first done by a system of
called
.
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Alphonse
anthropometry system used
body
measurements to identify
an individual
Fingerprints
History of Fingerprints
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Sir
invented a system for
fingerprints
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Allowed fingerprint records to be
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Based on
, so
matching one print
would be
Fingerprints
How are fingerprints analyzed?
Categorized by
and
Fingerprints
How are fingerprints analyzed?
Patterns
Arches
Arches are the simplest type of fingerprints that are formed by
ridges that
of the print and
.
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
. These patterns are named for their positions related
to the radius and ulna bones.
Delta
Ulnar Loop (Right
Thumb)
Loop opens toward
right or the ulna bone.
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
. They also have at least
. 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.
Fingerprints
How are fingerprints analyzed?
Minutiae – points where
Bifurcation
Dot
Ridge Ending
Island
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
Crossover
Core
Bifurcation (fork)
Ridge ending
Scar
Island
Delta
Pore
http://cnx.org/content/m12574/latest/properties.jpg
Fingerprints
compares the
location of these
minutiae.
Fingerprint Identification
• When minutiae on two different prints match, these are called
or
• There is
for the number of points of
identification required for a match
• However, the United Kingdom requires a minimum
sixteen points while Australia requires twelve.
(
)
AFIS is a computerized system capable of
reading, classifying, matching, and storing
fingerprints for criminal justice agencies. Quality
latent fingerprints are entered into the AFIS for a
search for possible matches against the state
maintained databases for fingerprint records to
help establish the identity of unknown deceased
persons or suspects in a criminal case.
http://www.fdle.state.fl.us/CrimeLab/images/fingerrint%20comparison%20for%20afis.jpg
Fingerprints
There are 3 types of fingerprints
– left by
1.
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Does not need processing
Fingerprints
There are 3 types of fingerprints
2.
tar, etc.)
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–
(butter, putty,
Does not need processing
Fingerprints
There are 3 types of fingerprints
3.
– requires
to make
visible and suitable for analysis
Fingerprints > Analysis
What are the invisible components?
Multiple
palms, etc.
secrete onto fingers,
Sweat contains:
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Inorganic ions (Na+, Cl -)
Proteins, amino acids
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Lipids
Other
Fingerprints > Analysis
Development and Collection:
Scene or Lab?
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No rule:
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Fingerprint
after
development (scene or lab)
Fingerprints > Analysis
Physical Development: Dusting
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Apply
to latent print or area.
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Powder
to print.
Brush and Powder
Magnetic Brush
and Powder
Fingerprints > Analysis
Chemical Development:
1.
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No longer used (messy, not sensitive)
Silver reacts with Cl - ions in print
Fingerprints > Analysis
Chemical Development:
2.
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Iodine sublimes
(solid → gas)
Iodine reacts with lipid
components; becomes
trapped in the print.
Fuming wand or chamber
Dirty Brown Color
Fingerprints > Analysis
Chemical Development:
3.
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Reacts with amino acids; purple color
Painted or sprayed on area
Heated to react
Fingerprints > Analysis
Chemical Development:
4.
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Fumes with heat or base (NaOH)
Fumed in cabinets
Off-white print
Fingerprints > Collection
Collection of prints:
:
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Tape placed over developed print
Tape then placed on white card.
Fingerprints > Collection
Collection of prints:
•
Sometimes a photograph will be the