Fingerprints3

Fingerprints3 - 8/11/10 Fingerprints
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Unformatted text preview: 8/11/10 Fingerprints
 Jeannette
M.
Perr,
Ph.D.
 Fingerprints
Outline
 •  History
 •  3
fundamental
principles
 •  Classification
members
 •  So
what
started
all
this
 interest?
 –  Wanted
a
way
to
identify
 people
that
was
foolproof
 1 8/11/10 Anthropometry
 •  Alphonse
Bertillon
 (1853‐1914)
developed
 what
became
known
as
 anthropometry
around
 1883
(remember
from
the
 introduction
lecture)
 •  The
first
systematic
 attempt
at
personal
 identification,
which
 utilized
detailed
 descriptions,
photographs,
 and
precise
body
 measurements
 Anthropometry
Measurements
 •  Alphonse
Bertillon
standardized
the
 mug
shot,
the
evidence
picture,
and
 developed
what
he
called
 photographie
métrique
(metric
 photography)
 •  This
system
to
allowed
precise
 reconstruction
of
a
particular
space
 and
the
placement
of
objects
in
it,
or
 to
measure
the
object
represented
 •  These
pictures
documented
a
crime
 scene
and
the
potential
clues
in
it
prior
 to
its
being
disturbed
 •  Bertillon
used
special
mats
printed
 with
cadres
métriques
(metric
frames)
 which
were
mounted
along
the
sides
 of
these
photographs
 •  Included
were
photographies
 stéréometriques
(stereometric
 photographs),
which
pictured
front
 and
side
views
of
a
particular
object
 2 8/11/10 Anthropometry
 •  Bertillon
believed
that
in
taking
11
precise
body
 measurements
along
with
systematic
photographs
 a
unique
profile
would
result
 •  This
was
the
first
rigorous
attempt
at
uniquely
 identifying
individuals.
 •  Precursor
to
what
we
now
know
as
biometrics
 •  However,
labor
intensive
and
susceptible
to
 human
error

 •  Best
thing
going
for
20+
years
 Sir
William
Herschel
(1858)
 •  English
administrator
in
India
 •  Began
placing
the
inked
palm
 impressions
and,
later,
thumb
 impressions
of
locals
on
 contracts.

 •  Used
as
a
form
of
signature
on
 the
documents
because
of
the
 high
level
of
illiteracy
and
 frequency
of
forgery
 •  Also
began
fingerprinting
 prisoners
in
jail
 3 8/11/10 Dr.
Henry
Faulds
(1874)
 •  Scottish
missionary
 doctor
working
in
 Japan
 •  First
to
suggest
 fingerprints
do
not
 change
 •  Tried
to
pioneer
 fingerprinting
for
 criminal
identification
 Francis
Galton
 •  Published
Finger
Prints
in
1892
 •  Finger
Prints
was
the
first
publication
to
 systematically
cover
the
anatomy
of
fingerprints
 and
methods
of
recording
them
 •  Proposed
classifying
intro
three
pattern
types:
 4 8/11/10 Failure
of
Bertillon
System
 Will
and
William
West
 •  Both
at
Fort
Leavenworth
prison
around
 1903
 •  Looked
like
identical
twins
(and
in
fact
they
 evidently
were)
 •  Body
measurements
were
indistinguishable
 •  Fingerprints
clearly
distinguish
the
two
 Fingerprint
Classification 
 Vucetich
System 
 Dr.
Juan
Vucetich 
 Argentina
1891 
 Spanish
speaking
countries 
 Henry
System 
 Sir
Edward
Richard
Henry 
 England
1897 
 English
speaking
countries 
 5 8/11/10 Fingerprint
Fundamentals
 1)  No
two
fingers
have
yet
been
found
to
 possess
identical
ridge
characteristics
 2)  A
fingerprint
will
remain
unchanged
during
 an
individual’s
lifetime
 3)  Fingerprints
have
general
ridge
patterns
 that
permit
themto
be
systematically
 classified
 Identification
by
fingerprints
 •  What
is
an
identification?

 •  What
is
a
class
characteristic?
 •  How
far
can
you
go
to
declare
an
identification?

 •  Items
at
a
crime
scene
sometimes
constituting
an
 identification
 –  Toolmarks
 –  Footprints
 –  Fingerprints
 –  DNA
 •  What
else?
 6 8/11/10 Find
Points
of
Comparison
 No
identical
ridge
characteristics
 7 8/11/10 Your
book
is
Wrong!
 Ridge ending Bifurcation Island Short ridge Lake Hook or spur Bridge Double bifurcation Trifurcation Opposed bifurcations Ridge crossing All
minute
are…
 •  Ridge
endings/beginnings
 •  Dots
 •  Bifurcations
 8 8/11/10 Ridge
Characteristics
 Fingerprints
remain
unchanged
 “….friction
ridge
patterns
remain
unchanged
naturally
 in
their
ridge
detail
during
the
lifetime
of
an
 individual.
The
ridge
patterns
begin
to
form
during
 pre‐natal
life
and
are
fully
formed
by
the
seventh
 month
of
fetal
life.”
 A.
Moenssens,
author
of
Fingerprint
Techniques,
 1971,
and
Fingerprints
and
the
Law,
1969.
 9 8/11/10 Ridge
patterns
can
be
classified
 •  Although
friction
ridge
patterns
 exhibit
an
infinite
variety
of
 detail,
they
fall
within
certain
 broad
classes
that
permit
police
 to
store
and
retrieve
millions
of
 prints
on
the
basis
of
their
 general
pattern:
loops,
arches,
 and
whorls
(L.A.W.)
 loops
 ≈
60%
 arches
 ≈
5%
 whorls
 ≈
35%
 LAW…
 •  Loops
 –  ulnar:
opens
towards
 little
finger
 –  radial:
opens
towards
 thumb
 •  The
pattern
area
of
the
loop
 is
surrounded
by
two
 diverging
ridges
known
as
 type
lines.
 •  The
ridge
point
at
or
nearest
 the
type‐line
divergence
is
 know
as
the
delta.
 •  All
loops
must
have
one
 delta
 10 8/11/10 LAW…
 •  Arches
 –  plain:
ridges
enter
one
side,
rise
in
center,
exit
 other
side
 –  tented:
similar
to
plain
arch,
except
sharp
rise
in
 center
 LAW
 •  Whorls
 –  Basically
everything
else
 –  4
types:
plain,
central
pocket,
double
loop,
and
 accidental
 11 8/11/10 Primary
Classification
 •  Part
of
the
Original
Henry
System
and
 adopted
by
FBI
 –  10‐finger
classification
scheme
 –  Yields
1,028
Groups
 –  Simply
based
on
presence
or
absence
of
 whorl
on
each
finger
 Primary
Classification
 R
index
 R
Thumb
 16
 R
Ring
 R
Middle
 8
 L
Thumb
 R
Little
 4
 L
Middle
 L
Index
 2
 L
Little
 L
Ring
 1
 X
 Y
 So,
for
example,
someone
who
had
a
whorl
on
R.
Ring
and
R.
Little:

 0
 0
 16
 8
 0
 8
 0
 4
 4
 0
 0
 2
 0
 0
 1
 1
=
9
 1
=
5
 •  Someone
who
only
had
arches
and
 loops
would
be
1/1.

 •  25%
of
the
population
falls
into
this
 category
 12 8/11/10 13 8/11/10 Automated
Fingerprint
 Identification
Systems
(AFIS)
 •  Implemented
starting
in
the
1980’s
 •  Digitally
encode
fingerprints
based
on
mapping
of
minutiae:

ridge
 endings
and
bifurcations.
→
Database
of
“file”
prints.

 •  Algorithms
return
a
“candidate
list”
of
best
matches
between
 “search”
(unknown)
and
“file”
prints
 •  Trained
fingerprint
expert
makes
final
determination
based
on
 visual
inspection
 Automated
Fingerprint
 IdentificationSystems
(AFIS)
 Advantages:
 •  High‐throughput,
High
speed
 •  “File
prints”
not
limited
to
known
suspects
(e.g.
 FBI
database
has
35
million
people
in
database)
 Challenges:
 •  Different
suppliers
have
slightly
different
 systems
 14 8/11/10 15 8/11/10 Fingerprints
in
Practice
 •  Methods
of
Locating
 Fingerprints
 •  Methods
of
 Developing
 Fingerprints
 •  Preservation
of
 Developed
Prints
 •  Digital
Imaging
and
 Enhancement
of
Prints
 Definitions
 •  Visible prints •  Made by touching a surface after the ridges have been in contact with a 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 (or invisible) prints •  Impressions caused by the transfer of body perspiration or oils present on finger ridges to the surface of an object •  Latent fingerprints are made from perspiration, sweat, oils, and amino acids 16 8/11/10 Visualizing
latent
prints
 Surface
Type
 Porous
 Non‐Porous
 Surface
Examples
 papers,
cardboard,
 cloth
 glass,
mirror,
tile,
 painted
surfaces
 Visualization
Methods
 chemical
 development:
I2,
 Ninhydrin
 RUV,
fingerprint
 powder

 Super
Glue®
 Locating
latent
prints
 RUVIS: Reflected Ultraviolet Imaging System Locates prints on non-porous surfaces by aiming UV light at surface. The reflected-back image is converted to visible light by an image intensifier. Latent print on sticky side of duct tape Latent prints on painted wall Illustration of Contrast Effect due to variation of illumination angle. Depending on what angle the user holds the light, a print can either appear white or black. 17 8/11/10 Visualizing
latent
prints
 •  Fingerprint Powders » » » » » used for non-porous surfaces lightly applied with camelhair or fiberglass brush adheres to oils/residue of fingerprint available in a variety of colors goal is have good color contrast with background surface; gray and black powder common Visualizing
latent
prints
 •  Other types of fingerprint powders » Magna brush / magnetic-sensitive powder -- for sensitive prints that might be damaged -- good for slightly textured surfaces: leather, plastic » Fluorescent powders -- designed to fluoresce under UV light -- creates better contrast with background surface color. 18 8/11/10 Chemical
Visualization
for
Porous
 Surfaces
 •  Iodine fuming •  oldest method •  sample is placed in developing chamber •  heated I2 (s) → I2 (g). “sublimation” •  visualization fades, “fix” stain with 1% aqueous starch solution. •  Ninhydrin •  forms a purple-blue color by reacting with trace amounts of amino acids in prints •  applied as a 0.6% solution in acetone •  visualization can be sped up with heat Chemical
Visualization
for
Porous
Surfaces
 •  Physical
Developer
 –  silver‐nitrate
based
liquid
 reagent
 –  destroys
proteins,
so
 should
be
used
only
after
 ninhydrin
is
 



 attempted
 •  Ninhydrin
substitutes
such
as
 DFO
(1,8‐diazafluoren‐9‐one)
 (left
side)
image
and
IND
(1,2‐ Indandione)
(right
side
 image)
 •  Viewed
under
green
light,
 through
a
dark
orange
filter
 19 8/11/10 Chemical
Visualization
 •  For non-porous surfaces (e.g. metals, electrical tape, leather, plastic bags, etc.): •  Super Glue (cyanoacrylate) fuming •  typically done in a chamber •  glue is heated to form a vapor •  vapor reacts to produce a whiteappearing print •  also combined with fluorescent dyes to aid visualization (e.g. rhodamine 6G) Fingerprint developed with cyanoacrylate, cut in half and stained with Rhodamine 6G (left side) and Basic Red 28 (right side) Alternate
light
sources
 “Crime-scopes”: Visualization based on fluorescence. Portable, high-intensity quartz halogen, xenon, or indium light sources Can be focused on area via fiber optic cable Can be passed through filters to aid visualization 20 8/11/10 Preservation
of
Developed
Prints
 1)  Once print has been visualized, a photograph should be taken before any further attempts at preservation. -- Adapters can generate 1:1 scale images 2)  If object can be transported, lay clear tape over print to preserve it. 3)  More commonly, “lift” the print with lifting tape. -- then place lifting tape on card with good background contrast Digital
Imaging
and
 Enhancement
of
Prints
 Problem:
Developed
latent
prints
from
a
crime
scene
are
 typically
imperfect.
 Solution:
Photographic
fingerprint
images
are
scanned/ digitized
and
once
stored
can
be
enhanced
electronically
 for
better
visualization.
 Potential
risk:
The
process
of
digital
manipulation
might
 improperly
alter
image
resulting
in
faulty
analysis

 21 8/11/10 Digital
Imaging
Concepts
 Pixels
(“Picture
elements”):
 Square
electronic
“dots”
which
comprise
image
file
 Bit
depth:
 
the
number
of
bits
used
to
define
each
pixel.
The
greater
the
 bit
depth,
the
greater
the
number
of
tones
(grayscale
or
color)
that
 can
be
represented
(e.g.,
12‐bit
=
4,096
tonal
variations)
 Resolution:
 
Represented
as
“pixel
dimensions”
(i.e.,
800
x
600),
or
“dpi”


 Digital
Image
Enhancement
 FFT:
“Frequency
(or
fast)
Fourier
Transform”
 
used
to
subtract
periodic
or
repetitive
background
patterns
 such
as
lines
or
dots
 22 8/11/10 23 ...
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This note was uploaded on 03/06/2011 for the course CHS 3501 taught by Professor Perr during the Spring '09 term at FIU.

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