Transcript Fingerprints notes

Fingerprints
What are Fingerprints?
• Fingerprints are impressions of the ridges of the fingertips deposited
on a surface in sweat or oil.
• No people have the exact same fingerprints due to the identity,
number, and location of minutiae!
•They form from pressure on a baby's tiny, developing fingers
in the womb during the 3rd to 4th month and NEVER change during
one’s lifetime.
Fingerprint Removal
• To avoid law enforcement many people have tried to remove their
fingerprints.
John Dillinger
In May 1934, John Dillinger, the infamous bank robber, hired a
lawyer to put him in touch with two surgeons willing to perform
plastic surgery on his face. The doctors performed the operation
at Dillinger’s cabin hideout. The gangster flew into a rage when
the bandages came off. He didn’t look any different. Enraged,
Dillinger threatened to shoot the physicians then changed his mind
when one of them suggested that he have his fingerprints burned
off with acid. Dillinger liked the idea and following the painful dipping
of his fingers into acid, it appeared that the process had worked.
A few months later Dillinger was shot to death by FBI agents in
Chicago. The medical examiner’s check of the body revealed that
the bank robber’s fingertips were scarred. His old ridge patterns,
however, were still visible. Even acid couldn’t remove fingerprints
permanently.
Fingerprint Removal
Roscoe Pitts
Roscoe Pitts, a criminal from the 1940’s, had all ten fingers
sutured to his chest for several weeks to cause growth of
smooth skin on his fingertips.
Fingerprint Classifications
• In the 1890’s Sir Francis Galton conducted extensive research
On fingerprints and convinced the English government to adopt
fingerprints as an additional way to identify people.
• He proposed the three major pattern types which we today.
Loops – 65%
Arches – 5%
Whorls – 30%
• There are several sub categories within each pattern.
Fingerprint Classifications
Loops:
• Ridge line enters and exits from the same side.
• The side the ridge enters and exits determines it name.
Radial Loop
Enters from thumb
Ulna Loop
Enters from little finger
Fingerprint Classifications
Arches:
• Ridges enter from one side of the finger and exit the other
while riding upward in the middle.
Plain Arch
Tented Arch
Fingerprint Classifications
Whorls:
• Any other pattern not classified as Arch or Loop is a Whorl.
Fingerprint Classifications
• Name the fingerprint classifications (left hand).
Arch
Whorl
Arch
Whorl
Radial Loop
Ulna Loop
Enters from thumb - Radial
Enters from little finger - Ulna
Ulna Loop
Name the following (right hand):
Arch
Whorl
Whorl
Ridge Classification
Arches, loops, and whorls are the general patterns (class evidence).
To make fingerprints individual we must look at the fine structure
of ridge characteristics called minutiae.
Common ridge characteristics
Ending Ridge
Bridge
Bifurcation
Trifurcation
Enclosure or Island
Dot
Spur
There are about 150 different ridge characteristics on a given
print. The core is the approximate center of the pattern.
Ridge Classification
Number and location of minutiae make fingerprints unique.
Types of Fingerprints
Plastic Prints are made from pressing a finger into a material such:
• clay
• soap
• candle wax
Visible Prints are made by touching a colored material such as:
• blood
• ink
• paint
• grease
• ink
Latent Prints are essentially invisible and must be developed by
chemical or physical means.
• they result from deposits of perspiration and body oils.
Visualizing Latent Prints
Dusting used on nonporous surfaces
Visualizing Latent Prints
Chemical Processes used on porous surfaces
Super Glue Fuming
• reacts with print residue
turning the print white.
Ninhydrin
• reacts with amino acids
left by finger.
• turns latent print pink or
orange.
• used on porous surfaces
such as paper.
Comparing Prints
Despite technology
a person still is needed to
declare a match.
Generally 8 – 14 points of
similarity are needed to
consider a match.
Modern Fingerprinting Techniques
What is AFIS?
• AFIS is an acronym for:
Automated Fingerprint Identification System
• This system is maintained by the FBI's Criminal Justice
Information Services Division.
• System can be accessed 24/7 by
local law enforcement agencies.