Fingerprints
Chapter 4
Objectives
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You will understand:
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Why fingerprints are individual evidence.
Why there may be no fingerprint evidence at a crime scene.
How computers have made personal identification easier.
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WARNING
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THERE ARE MANY CASE STUDIES IN THIS CHAPTER
THERE ARE A COUPLE LOOONG AND DIRTY LABS
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At the Crime Scene
What evidence could link the
burglar to the burglary?
Make a list.
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at this scene:
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fingerprints, footprints, bite marks, pry mark impressions,
fabric, blood, handwriting
with suspect:
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fingerprints, shoe prints, pry bar, dog hair, torn shirt sleeve,
blood type, DNA, handwriting and poor spelling, damaged
pants, leg wound, broken glass, soil, stolen jewelry, teeth
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Right now: We focus on the prints.
What is a fingerprint?
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pattern of ridges from last digit of person’s fingers
Why useful for identification?
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has unique characteristic ridges
stays for a person for a lifetime
a systematic classification is used for id’ing people
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The History of Fingerprints
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used long ago as a signature for legal stuff
has been known for millennia, but only
recently became a study called
dactyloscopy...
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William Herschel (19th century)
required Indians (from India) to put their
fingerprints on contracts, and used
fingerprints as a means of identifying
prisoners
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Henry Faulds claimed
that fingerprints did not
change over time
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(why was that a big insight?)
they could be classified for
identification of criminals
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But before fingerprinting was used
to ID, this was popular...
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Alphonse Bertillon (1880‘s)
proposed body measurements as
a means of identification; termed
anthropometry
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He suggested using eleven body
measurements to id
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By end of century was accepted
virtually everywhere
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In 1890‘s, Francis Galton
developed a primary
classification scheme based
on loops, arches, and whorls
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IMPORTANTLY, he saw
that the prints don’t change
over a lifetime, no two are
identical, they cannot be
altered, and they can be
systematically classified!!!
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Edward Richard Henry, in
collaboration with Galton,
instituted a numerical
classification system
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gave us Henry classification
system which replaced
Bertillon’s method
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Scotland Yard adopted it in
1901
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Juan Vucetich - developed a fingerprint
classification system based on Galton’s that is
used in Spanish-speaking countries
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first to officially ID a criminal
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she confessed
Francesca Rojas had murdered her two sons,
blamed a neighbor but left her bloody
fingerprints on a doorpost
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Francesca Rojas’ prints (Prints of Evil)
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why not use Bertillon’s anymore?
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1903 a man named Will
West was taken to
Leavenworth
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he was measured using
Bertillon’s methods
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his numbers matched
another prisoner...
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named William West
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not only did their measurements almost perfectly match...
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...they looked similar
their fingerprints
conclusively
determined who was
who
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finally, in the early 1900’s fingerprinting
became the thing to do
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in 1924, the Identification Division of
the FBI was formed
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by 1946, 100 million fingerprints, today
>250 million
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quick quiz
1. T/F Our fingerprints change after about the age of 40.
2. What is the fancy-schmancy science term for studying
fingerprints?
3. Who gave us a way of identifying a person by different body
measurements?
4. Who was the first person to solve a crime by using fingerprints?
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The Anatomy of Fingerprints
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your skin on your fingers, palms, feet,
and lips have “friction ridges”
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they are yours and yours alone
(even twins have their own; not
genetically controlled!)
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skin has an outer layer (epidermis)
the papillae separate the outer layers from the inner
they make the ridges and grooves
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when you perspire out of
the tiny pores, the water
evaporates leaving the
smallest amount of salt,
amino acids, lipids, and
whatever oils you picked up
from scratching your head
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Classification of Fingerprints
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All comes down to this:
LOOP
WHORL
ARCH
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loops
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A loop must have one or more ridges
entering and exiting from the
same side.
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Types (JUST FYI):
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radial - opens toward the thumb
(the side of the radius armbone)
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ulnar - opens toward the little
finger (the ulna bone side)
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loops
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loops must have one delta (∆)
C
and a core
both locations are needed for ID
D
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whorls
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whorl fingerprint pattern with
at least two deltas and a core
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a delta-to-delta line hits core
ridges
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several types...
C
D
D
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whorl
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“double loop” has... derp, two
loops
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actually a whorl!
C
D
D
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whorls
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C
central pocket loop
D
this is kind of a mutant
a delta-to-delta line hits no core
ridges
D
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arch
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the arch pattern is made up of
ridges lying one above the other in
a general arching formation.
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no core, no delta
here plain arch...
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arch
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the tented arch
looks like... a tent ;)
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nice little summary
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Lab Activity 4.1
LAB ACTIVITY 4.1
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Deputy Bailey is here to help.
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If you want to do the print card
yourself, practice first on a
sheet of paper til you get it
down. I only have enough cards
for everyone to get one.
#1 Make sure you do the
observations and record them
on your lab
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#2 You can cut and paste if you
want or print directly to card.
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#3 Do it!
Do your lab as described
in the handout!!! Since there
are not enough scopes and
magnifying glasses, you might
start with #2.
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the henry classifcation
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How did they weed out all of the b-zillions of
fingerprint records???
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look to the whorls!!!
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R
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each finger is assigned a
number; if there is a
whorl, score it with
the points for that
finger!
L
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e.g. there is a whorl on your left thumb and your right middle finger;
all others are loops or arches...
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this is the primary Henry-FBI classification number
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R
L
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R
L
9
2
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Calculate your Henry-FBI classification number...
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quick quiz
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Answer loop, whorl, or arch
1. Which can be classified as radial or ulnar?
2. Which have two deltas and one core?
loop
whorls
3. Which can be “tented”?
arch
4. Which have no core or delta?
arch
5. Which have one delta and one core?
loop
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ridge classification
(individualization)
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so far, a general look at prints:
now minutiae
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this is really what makes your
prints unique
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buckle your seatbelts...
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ID the 15
points of
minutiae on
the handout
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write answers
on Action
Hero
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presenting prints as evidence
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no present legal requirement for
matching prints
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actually matching 8-12 points is
enough
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“fingerprints” cannot lie, but we can
make mistakes
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so, must try and get a good print, and
then read it well...
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What about boo-boo’s, scars,
missing fingers?
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The prints of laborers who work in
alkaline (basic) conditions can
become faded after a while
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Many criminals have tried to
obliterate
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John Dillinger was famous for
getting his prints disfigured...
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One way to get prints….
(warning: you may not like this)
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Types of Prints
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plastic, visible, latent
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like wax, soap, gum, candy bar, clay
a plastic print is a 3D sort of print made
from impressions on something “plastic”
or moldable
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visible print is left by a finger that has
touched some colored material, like
blood, paint, ink, grease chalk, mud, dust
latent print is invisible and has to be
brought out through chem or physical
means...
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Visualizing Latent Prints
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one of the most common way to
visualize for nonporous surfaces?
dust it!
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choose contrasting powder (black
on light, white on dark, or grey to
get either)
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“lift” the print with clear, sticky tape
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use chemical methods for porous surfaces
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iodine (older method) reacts with fatty acids (but
doesn’t show for long)
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ninhydrin reacts
with amino acids
to form orange to
purple print
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silver nitrate reacts with NaCl in print to form silver
chloride, then oxidizes to black silver oxide
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then there is superglue...
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superglue is a
cyanoacrylate ester that
binds to print residue to make
permanent white print
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you can then treat with
powders or fluorescent dye
to bring out the print
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cyanoacrylate
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a quick look at other techniques...
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cyanoacrylate with blue/green
fluorescent dye
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cyanoacrylate with rhodamine
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cyanoacrylate + fluorescent RAM
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fluorescent DFO
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fingerprints + fluorescent powder
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+ laser light
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bloody fingerprint sprayed with
merbromin + hydrogen peroxide
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other methods
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photographing prints can help greatly especially with all the
photoshop type of apps that are available
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digital prints are taken all the time now for suspects in
custody
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the prints are scanned and sent to AFIS...
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4.2 Write-Up
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Title
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Either clear tape prints or use
glue sticks, and sheet protectors
on graph paper in pen
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All prints will be nicely arranged,
clearly labeled (I mean it!!!)
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Don’t worry about identifying
ridge characteristics. Just have
all the prints, nicely done,
nicely arranged and
labeled. Really. No joke.
Purpose (from p 88)
Procedure (“Refer to...”)
PHYSICAL METHODS
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all four prints from Station
One prints, neat and labeled
CHEMICAL METHODS
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Iodine Fuming
Ninhydrin
Superglue Fuming
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AFIS
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The Automated Fingerprint Identification
System — a computer system for storing and
retrieving fingerprints
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Established in the 1970s, AFIS enables law enforcement
officials to search large files for a set of prints taken
from an individual
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By the 1990s, most large jurisdictions had their own system
in place. The problem: A person’s fingerprints may be in one
AFIS database but not in others.
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now the FBI has Integrated Automated Fingerprint
Identification System
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can take a Live Scan (only costs $15-20K)
compares to 55 million+ prints
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other “prints”
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Lips - several common
patterns
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Voice - electronic pulses
measured on a
spectrograph
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Foot - size of foot and
toes; friction ridges on the
foot
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Shoes - can be compared
and identified by type of
shoe, brand, size, year of
purchase, and wear
pattern (more later)
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Palm - friction ridges can
be identified and may be
used against suspects
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Footprints are taken at
birth as a means of
identification of infants.
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Teeth - bite marks are
unique and can be used to
identify suspects. These
imprints were placed in
gum and could be
matched to crime scene
evidence. (more later)
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The blood vessel patterns in
the eye may be unique to
individuals. They are used
today for various security
purposes.
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EOCS
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Don’t forget to do #1!
but not #2
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