Transcript Ch 4 Forensic Science of Fingerprints

Forensics of Fingerprints
“commonly used forensic
evidence worldwide”
• A fingerprint is the impression made by the
papillary ridges on the ends of the fingers and
thumbs. the ridge arrangement on every
finger of every human being is unique and
does not alter with growth or age.
Where do you have ridges?
• Any ridged area of the hand or
Ridges
• Each ridge of the epidermis (outer skin) is dotted
with sweat pores. The epi dermis is anchored to
the dermis (inner skin) by peglike
protuberances, or papillae.
• Injuries such as superficial burns, abrasions, or
cuts do not affect the ridge structure and the
original pattern is seen in any new skin that
grows.
• An injury that destroys the dermal papillae,
however, will alter the ridges.
History of Fingerprinting
• Prehistoric
• In ancient Babylon, fingerprints were used on
clay tablets for business transactions.
• In ancient China, thumb prints were found on
clay seals.
• In 14th century Persia, various official
government papers had fingerprints
(impressions), and one government official, a
doctor, observed that no two fingerprints were
exactly alike
1882 - Bertillon
• devised a system of
classification, known as
Anthropometry or the
Bertillon System,
• using measurements of
parts of the body.
• measurements such
as head length, head
width, length of the
middle finger, length of
the left foot; and length
of the forearm from the
elbow to the tip of the
middle finger.
History of Fingerprinting
• Early anatomists described the ridges of
the fingers
• But interest in modern fingerprint
identification dates from 1880, when the
British scientific journal Nature published
letters describing the uniqueness and
permanence of fingerprints.
History of Fingerprinting
• Their observations were experimentally
verified by the English scientist Galton,
who suggested the first system for
classifying fingerprints based on
grouping the patterns into arches,
loops, and whorls.
History of Fingerprints
• The Galton-Henry system of fingerprint
classification, published in June 1900, was
officially introduced at Scotland Yard in 1901
• It quickly became the basis for its criminalidentification records.
• Now the most widely used method of fingerprint
classification.
Fingerprint Classification
• Fingerprints are classified in a threeway process:
– by the shapes and contours of individual
patterns,
– by noting the finger positions of the
pattern types,
– by relative size, determined by counting
the ridges in loops and by tracing the
ridges in whorls.
Dactyloscopy
• is the technique of fingerprinting, involves cleaning the
fingers in benzene or ether,
• drying them,
• then rolling the balls of each over a glass surface coated
with printer's ink.
• Each finger is then carefully rolled on prepared cards
according to an exact technique designed to obtain a
light gray impression with clear spaces showing between
each ridge so that the ridges may be counted and
traced.
• Simultaneous impressions are also taken of all fingers
and thumbs.
Latent Fingerprinting
• involves locating, preserving, and identifying impressions left by a
culprit in the course of committing a crime.
• In latent fingerprints, the ridge structure is reproduced not in ink on a
record card but on an object in sweat, oily secretions, or other
substances naturally present on the culprit's fingers.
• Most latent prints are colourless and must therefore be "developed,"
or made visible, before they can be preserved and compared.
• This is done by brushing them with various gray or black powders
containing chalk or lampblack combined with other agents.
• The latent impressions are preserved as evidence either by
photography or by lifting powdered prints on the adhesive surfaces
of tape.
Fingerprint Principles
According to criminal investigators, fingerprints
follow 3 fundamental principles:
• A fingerprint is an individual characteristic; no
two people have been found with the exact same
fingerprint pattern.
• A fingerprint pattern will remain unchanged for
the life of an individual; however, the print itself
may change due to permanent scars and skin
diseases.
• Fingerprints have general characteristic ridge
patterns that allow them to be systematically
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
Loop
Radial Loop
Ulnar loop
Whorl
Plain whorl
Central pocket whorl
Double loop whorl
Accidentical
Interesting Info
Fingerprint Factoid:
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.
Arches
Arches are the simplest type of fingerprints that are formed by
ridges that enter on one side of the print and exit on the other. No
deltas are present.
Spike or “tent”
Plain Arch
Ridges enter on one side and
exit on the other side.
Tented Arches
Similar to the plain arch,
but has a spike in the center.
Loops
Loops must have one delta and one or more ridges that enter and
leave on the same side. These patterns are named for their positions
related to the radius and ulna bones.
Delta
Ulnar Loop (Right
Thumb)
Loop opens toward
right or the ulna bone.
Radial Loop (Right
Thumb)
Loop opens toward the
left or the radial bone.
NOTE: On the left hand, a loop that opens to the left would be an ulnar
loop, while one that opens to the right would be a radial loop.
Whorls
Whorls have at least one ridge that makes (or tends to make) a
complete circuit. They also have at least two deltas. If a print has
more than two deltas, it is most likely an accidental.
Plain
Whorl
Central
Pocket
Whorl
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.
Whorls – Part 2
Double Loop Whorl
Accidental Whorl
Delta
Delta
Double loop whorls are
made up of any two loops
combined into one print.
Accidental whorls contain two
or
more
patterns
(not
including the plain arch), or
does not clearly fall under any
of the other categories.
Identify each fingerprint pattern.
Right Hand
Left Hand
Right Hand
Right Hand
Left Hand
• . There are at least 150
individual ridge
characteristics on the
average fingerprint. 10 to
16 specific points that
match exactly are needed
for ID.
Fingerprints in the Population
• Loops about 65 percent of the total
fingerprint patterns;
• whorls make up about 30 percent
• arches and tented arches together
account for the other 5 percent.
• The most common pattern is the ulnar
loop.
Three Kinds of CRIME-SCENE
Prints
• 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. True 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.
The most common techniques
used to find latent or hidden
fingerprints
• 1. Dusting with Carbon Powder on white or light colored
surfaces.
• 2. Dusting with Lanconide Powder for black surfaces.
• 3. Dusting with Aluminum Powder for hard or dark
colored surfaces as well as mirrors and metal surfaces.
• 4. Use of (Super-glue) fuming.
• 5. Use of Iodine fuming techniques.
• 6. Use of ninhydrin.
• 7. Use of Silver Nitrate.
• 8. Use of Laser technology.
Tools
• Optical scanners identify the print using
light; depending on the brightness of the
reflected light, optical scanners depict
ridges as dark and valleys as light.
• Capacitance scanners determine the print
by using an electrical current. Valleys and
ridges on the fingers produce different
voltage output, allowing for discrimination
between them.
Tools
• A number of portable fingerprint scanners
were developed mainly by computer
companies to provide a secure access for
the users.
• In 1998, Compaq was the first to have a
print reader attached to the computer
Tools
• New scanner trials are on the way to
provide the same protection for ecommerce and Internet banking in order to
secure transactions.
• In order to combat cell phone thefts, the
industry is considering equipping phones
with fingerprint readers.
• Five U.S. airports, including Chicago's
O'Hare have installed finger-print scanners
to check employees' backgrounds.
• Some banks use fingerprint scans before
a check is cashed.
• Similarly, government agencies
sometimes utilize fingerprint scans to
ensure that payments are given to the
proper recipients.