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FORENSIC SCIENCEFORENSIC SCIENCEPrintsPrints
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PrintsDactyloscopy: 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?
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 Principlesof Fingerprints
A fingerprint is an individual
characteristic.
A fingerprint will remain unchanged
during an individual’s lifetime.
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
RIDGE ENDINGBIFURCATION
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MINUTIA
SHORT RIDGE DOT or ISLAND
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 right hand? Left hand?
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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
Loops: 65% Whorls: 30% Arches: 5%
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Primary Identification Numbers- NOTE: fix this slide in your packet
1. right 2. right 3. right 4. right 5. right thumb index middle ring little
16 16 8 8 4
6. left 7. left 8. left 9. left 10.leftthumb index middle ring little
4 2 2 1 1
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.
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Primary Identification (cont) NOTE: fix this slide in your packet
2. right 4. right 6. left 8. left 10. left index ring thumb middle little
16 8 4 2 1
16 8 4 2 1
1. right 3. right 5. right 7. left 9. left thumb middle little index ring
Set up a ratio of even numbered fingers over odd numbered, adding one in both the numerator and denominator.
+ 1
1
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Fingers
1
1 2 2
416
16 88
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
Ears--shape, length and width
Face--pictures being used in Florida to find criminals
Voice--electronic pulses measured on a spectrograph
Feet--size of foot and toes; lines of the feet
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
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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