Transcript FORENSIC SCIENCE - Mount Mansfield Union High School

FORENSIC SCIENCE
Prints
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Prints
Dactyloscopy: the study of
fingerprints

Making Prints
– Rolling prints
– Modus Operandi--primary identification number

Lifting Prints
– Black, white and fluorescent powder
– Chemicals--ninhydrin, iodine, silver nitrate, cyanoacrylate

Other Types of Prints
– Palm, lip, teeth, eye, ear, voice, shoe and feet prints
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What is a Fingerprint?

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Skin has an outer layer (epidermis) which has
ridges projecting inward, and an inner layer
(dermis) which has projections pressing into the
spaces between ridges
A fingerprint is a pattern made by the friction
ridges, which is left behind due to sweat and oil
that sticks to them.
Fingerprints form during the fetal stage of
development.
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Fundamental Principles
of Fingerprints

A fingerprint is an individual
characteristic.
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A fingerprint will remain unchanged
during an individual’s lifetime.
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Fingerprints have general
characteristics ridge patterns that
permit them to be systematically
classified.
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Ridge Characteristics
Minutia--lines of the fingerprint
ridge ending
bifurcation
short ridge
dot or island
enclosure
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MINUTIA
BIFURCATION
RIDGE ENDING
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MINUTIA
DOT or ISLAND
SHORT RIDGE
ENCLOSURE
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Arch
An arch has friction ridges
that enter on one side of
the finger and cross to
the other side while
rising upward in the
middle.
Types
Plain- the arch is mild
Tented- the arch is
spiked upward
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Plain arch
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Tented arch
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Loop
A loop must have one or more
ridges entering and exiting from
the same side it began. Loops
must have one delta (a“Y”
pattern from diverging ridges)
Types
Radial--opens toward the thumb
Ulnar--opens toward the “pinky”
(little finger)
Which type of loop is this, if on the
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right hand? Left hand?
Whorl
A Whorl has a minimum of 2
deltas.
Types
 Plain- 2 symmetric deltas and a
complete ridge circuit (circular in
pattern)
 Central Pocket- 2 asymmetric
deltas, one side appears to be
stretched
 Double Loop- 2 loops and 2 deltas
 Accidental- a whorl that does not
fit the 3 above pattern types
Plain whorl
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Central Pocket Whorl
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Double Loop (whorl)
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Accidental whorl
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Human population fingerprint
distribution
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Loops: 65%
Whorls: 30%
Arches: 5%
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Primary Identification
Numbers- NOTE: fix this slide in your packet
Fingers are numbers 1 through 10 starting with the thumb on the
right hand and continuing through with the thumb on left hand.
Each finger is then given a point value as seen in the chart below.
1. right
thumb
2. right
index
16
16
6. left
thumb
7. left
index
4
2
3. right
middle
4. right
ring
5. right
little
8
8
4
8. left
middle
2
9. left
ring
1
10.left
little
1
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Primary Identification (cont)
NOTE: fix this slide in your packet
Set up a ratio of even numbered fingers over odd numbered,
adding one in both the numerator and denominator.
2. right
index
16
4. right
ring
8
6. left
thumb
4
16
8
4
1. right
thumb
3. right
middle
5. right
little
8. left
10. left
middle
little
2
2
7. left
index
1
1
+
9. left
ring
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1
1
Fingers
1
2
2
16
1
16
8
8
4
4
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Latent Prints
Latent fingerprints are those that are “hidden”
and are not visible to the naked eye. These
prints consist only of the natural secretions of
human skin and require treatment to cause
them to become visible.
Most secretions come from three glands:
Eccrine--largely water with both inorganic
(ammonia, chlorides, metal ions, phosphates) and
organic compounds (amino acids, lactic acids, urea
sugars)
Apocrine--secrete cytoplasm and nuclear materials
Sebaceous --secrete fatty or greasy substances.
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Lifting Latent Prints
Developing a print requires chemicals that react
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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Iodine Fingerprint
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Ninhydrin Fingerprint
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Lifting Latent Prints (cont)

Ninhydrin--reacts with amino acids to produce a purple
reaction.
Silver nitrate--react with chlorides 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.
In modern labs and criminal investigations, lasers and
alternative light sources are used to view latent fingerprints. It
was first used by the FBI in 1978. Since lasers can damage the
retina of the eye, special precautions must be taken and a filter
used.
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Cyanoacrylate Fingerprints
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Other Prints
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Ears--shape, length and width
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Face--pictures being used in Florida to find criminals
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Voice--electronic pulses measured on a spectrograph
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Feet--size of foot and toes; lines of the feet
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Shoes--can be compared and identified by type of
shoe, brand, size and year of purchase
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Other Prints
Palm--lines can be
identified and may be
used against suspects.
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Other Prints
Foot Prints are taken at
birth as a means of
identification for
infants.
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Other Prints
The study of lip-prints is
called cheiloscopy
Lips--display one of five
common patterns
Short vertical lines
Long vertical lines
Rectangular lines that
may crisscross
Diamond
Branching
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Other Prints
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The use of lip prints is not yet firmly
established in our courts.
Two ways to potentially use lip prints:
– 1- print patterns for identification
– 2- chromatography to match lipstick marks
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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 may be
unique to individuals.
They are used for
today various security
purposes.
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“FINGERED”
Crazy Criminals
A New Jersey resident phoned
police after finding her back door
slightly ajar with a muddy palm
print on the glass. When the
officer questioned the woman, it
was determined that she had
been gardening. When he
compared her hand with the
lifted print, he had a match!!
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