Transcript Chapter 4 - mmartinscience

Chapter 4:
Fingerprints
“Fingerprints can not lie,
but liars can make
fingerprints.”
—Unknown
Fingerprints
Students will learn:
 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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Fundamental Principles
of Fingerprints
 A fingerprint is an individual
characteristic.
 A fingerprint will remain unchanged
during an individual’s lifetime.
 Fingerprints have ridge patterns that
allow them to be classified and entered
into a national database.
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Interesting Info
60% of people have loops, 35% have whorls,
and 5% have arches
Did you know?
Dactyloscopy is the study of fingerprint identification.
Police investigators are experts in collecting
“dactylograms”, otherwise known as fingerprints.
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Ridge Characteristics
Minutiae—characteristics of ridge patterns
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Ridge ending
Short ridge
Dot or fragment
Bifurcation
Double bifurcation
Trifurcation
Bridge
Island
Enclosure
Spur
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Fingerprint Minutiae
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Fingerprint Classes
There are 3 specific classes for all fingerprints based
upon their visual pattern: arches, loops, and whorls.
Each group is divided into smaller groups
as seen in the lists below.
Arch
Plain arch
Tented arch
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Loop
Radial Loop
Ulnar loop
Whorl
Plain whorl
Central pocket whorl
Double loop whorl
Accidentical
Arch
 An arch ridges that
enter on one side of the
print and exit on the
other.
 No deltas are present.
 Types:
 Plain
 Tented
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Arch Types
“tent”
Plain Arch
Ridges enter on one side and
exit on the other side.
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Tented Arches
Similar to the plain arch,
but has a spike in the center.
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Loop
 A loop must have one or
more ridges entering and
exiting from the same side.
 Types:
 Radial—opens toward the
thumb
 Ulnar—opens toward the
“pinky” (little finger)
 Which type of loop is this, if it
is on the right hand? Left
hand?
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Loop types
Delta
Ulnar Loop (Right
Thumb)
Loop opens toward
right or the ulna bone.
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Radial Loop (Right
Thumb)
Loop opens toward the
left or the radial bone.
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Whorl
 A plain or central pocket whorl
has at least one ridge that
makes a complete circuit.
 A double whorl is made of two
whorls.
 An accidental is a pattern not
covered by other categories.
 Whorls have at least two deltas
and a core.
 Types
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Plain
Central Pocket
Double Loop
Accidental
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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.
Plain Whorl
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Central Pocket Whorl
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Double Whorl
Double loop whorls are
made up of any two loops
combined into one print.
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Accidental Whorl
Accidental whorls contain two
or
more
patterns
(not
including the plain arch), or
does not clearly fall under any
of the other categories.
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Identify each fingerprint pattern.
Right
Hand
Left Hand
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Right
Hand
Right
Left Hand
Fingerprint Comparison
There are at least 150-200 individual ridge
characteristics on the average fingerprint.
8 to 12 specific points that match exactly
are required by most criminal courts as a
positive ID.
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AFIS
 The Automated Fingerprint Identification System - a
computer system for storing and retrieving
fingerprints
 By the 1990’s most large jurisdictions had their own
system in place. The problem - a person’s
fingerprints may be in one AFIS but not in others
 IAFIS—the FBI’s Integrated Automated Fingerprint
Identification system which is a national database of
all 10-print cards from all over the country
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3 Kinds of CRIME-SCENE
Prints
1. VISIBLE PRINTS which are prints made by fingers
that touched material such as blood, paint, grease, or
ink.
2. PLASTIC PRINTS which are ridge impressions left
on a soft material such as putty, wax, soap, or dust.
3. LATENT PRINTS which are invisible print
impressions caused by the perspiration on the ridges of
one’s skin. Perspiration contains water, salt, amino
acids, or oils and easily allows impressions to be made.
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Latent Prints
 Latent fingerprints are those that are
not visible to the naked eye.
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Developing Latent Prints
 Developing a print requires substances that interact
with secretions that cause the print to stand out against
its background.
 It may be necessary to attempt more than one
technique, done in a particular order so as not to
destroy the print.
 Powders—adhere to both water and fatty deposits. Choose a
color to contrast the background.
 Iodine—fumes react with oils and fats to produce a temporary
yellow brown reaction.
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Developing Latent Prints
 Ninhydrin—reacts with amino acids to produce a purple
color.
 Silver nitrate—reacts with chloride to form silver chloride,
a material which turns gray when exposed to light.
 Cyanoacrylate—“super glue” fumes react with water and
other fingerprint constituents to form a hard, whitish
deposit.
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Iodine Fingerprint
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Ninhydrin Fingerprint
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Cyanoacrylate Fingerprints
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Primary Classification
The Henry—FBI Classification
Each finger is given a point value
right
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left
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Primary Classification
Assign the number of points for each finger that has a
whorl and substitute into the equation:
right
index
right
ring
left
thumb
left
left
middle little + 1
right
thumb
right
middle
right
little
left
index
left
ring
=
+1
That number is your primary classification number
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Other Prints
 Ears—shape, length and width
 Voice—electronic pulses measured on a
spectrograph
 Foot—size of foot and toes; friction ridges on the foot
 Shoes—can be compared and identified by type of
shoe, brand, size, year of purchase, and wear pattern.
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Other Prints
Palm—friction ridges
can be identified and
may be used against
suspects.
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Other Prints
Footprints are
taken at birth as a
means of
identification of
infants.
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Other Prints
Lips—display several
common patterns
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Short vertical lines
Short horizontal lines
Crosshatching
Branching grooves
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Other Prints
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.
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Other Prints
The blood vessel
patterns in the eye
may be unique to
individuals. They are
used today for various
security purposes.
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Biometrics
 Use of some type of body metrics for the purpose of
identification. (The Bertillon system may actually have been
the first biometry system.)
 Used today in conjunction with AFIS
 Examples include retinal or iris patterns, voice recognition,
hand geometry
 Other functions for biometrics—can be used to control entry
or access to computers or other structures; can identify a
person for security purposes; can help prevent identity theft
or control social services fraud.
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More about Prints
For additional information about prints and
crime, check out Court TV’s Crime Library
www.crimelibrary.com/criminal_mind/forensics/fin
gerprints/1.html
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