Transcript fingerprints - Liberty Union High School District

Fingerprints &
Footprints
Chapter 4
Introduction
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Fingerprints are a unique pattern of ridges and
depressions on the tips of the fingers.
They can positively identify that a single person made
that print.
In the over 140 years that fingerprints have been
routinely compared worldwide, no two areas of friction
skin on any two persons (including identical twins)
have been found to contain the same individual
characteristics in the same unit relationship.
Other visible human characteristics change fingerprints do not.
Introduction
Fingerprints offer an infallible means of
personal identification.
 The fingerprint was recognized in Ancient China
where it was used to forge contracts.
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Fingerprints as Forensic Science
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Fingerprints outperform DNA and all other
human identification systems to identify more
murderers, rapists and other serious offenders
(fingerprints solve at least ten times more
unknown suspect cases than DNA in most
jurisdictions).
Where can fingerprints be found?
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Fingerprints from crime scenes have been identified
on
 Papers
 Cigarettes
 Fruit
 crumpled
aluminum cans
 plastic garbage bags
 bed sheets
 Rocks
 dead bodies (prints on bodies are usually contaminated
prints involving body fluids, lipstick or some other substance
transferred via the suspect's fingers)
How Long Do Fingerprints Last?
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Fingerprints on paper, cardboard and unfinished
wood can last for up to forty years (per actual
casework histories) unless exposed to water
(and contaminate transfer prints can even then
sometimes persist).
Fingerprints on non-porous surfaces such as
plastic, metal and glass can last for many years
if not exposed to water and if left undisturbed.
Formation
Fingerprint ridges are formed during the third to
fourth month of fetal development.
 These ridges consist of individual
characteristics called
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 Ridge
endings
 Bifurcations
 Dots
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The unit relationship of individual characteristics
does not naturally change throughout life
Classifying Fingerprints
Sir Frances Galton, Edward Henry, and
Juan Vucetich are all three responsible for
classifying fingerprints.
 Why is this so important?
 Loops
 Arches
 Whorls
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65% of the population have ridge patterns that
form loops.
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Approximately 30 percent of the population
has whorls
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5 % have arches
arches – follow a smooth wave like pattern
 Tented arches – contain a sharp point at the
center
 Plain
Revealing & Recording Prints
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Three main categories of fingerprints:
Visible – you can see them (paint, ink)
2. Plastic – made in soap wax or putty
3. Latent – The most common type and hidden to
the eye.
1.
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Latent prints are made when natural oils and
perspiration present between the fingerprint
ridges are transferred to a surface by touch.
Revealing & Recording Prints
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Methods of lifting prints
 Dusting
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with powder
Different types of powder and different colors
 Chemical
Use of superglue or cyanoacrylate. Easy to use, low
cost. Remarkable results
 Use of ninhydrin spray that forms a purple color when
combined with traces of amino acids in human
perspiration. Used on paper and cardboard
 Amido black, a dye sensitive to blood and may be used
with contaminated/visible prints
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The FBI
FBI maintains AFIS
 The FBI's Integrated AFIS (IAFIS) in
Clarksburg, WV has more than 49 million
individual computerized fingerprint records
for known criminals.
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Fingerprinting the Dead
Pathologists finger print the dead during
autopsies.
 Sometimes reconstructive work has to be
done in order to retrieve the fingerprints.
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Other Identifiers
Palm prints, feet prints
 Has anyone as a
baby had their feet
inked at the
hospital?
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