Fingerprints
Jan 20, 2016
Fingerprints
What are Fingerprints?
• Fingerprints are impressions of the ridges of the fingertips depositedon 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 fingersin 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 theirfingerprints.
John DillingerIn 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 dippingof 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 fingerprintspermanently.
Fingerprint Removal
Roscoe Pitts
Roscoe Pitts, a criminal from the 1940’s, had all ten fingerssutured 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 adoptfingerprints 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 ClassificationsLoops:
• Ridge line enters and exits from the same side.
• The side the ridge enters and exits determines it name.
Ulna LoopRadial Loop
Enters from thumb Enters from little finger
Fingerprint Classifications
Arches:
• Ridges enter from one side of the finger and exit the otherwhile 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 Arch WhorlRadial Loop
Enters from thumb - Radial
Enters from little finger - Ulna
Ulna Loop
Name the following (right hand):
WhorlWhorl
ArchUlna LoopWhorl
Ridge Classification
Arches, loops, and whorls are the general patterns (class evidence).
To make fingerprints individual we must look at the fine structureof ridge characteristics called minutiae.
Common ridge characteristics
Ending Ridge
Bifurcation
Bridge
Enclosure or Island
Spur
Trifurcation
Dot
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• paint• ink
• ink• grease
Latent Prints are essentially invisible and must be developed bychemical 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 Ninhydrin
• reacts with amino acidsleft by finger.• turns latent print pink ororange.• used on porous surfacessuch as paper.
• reacts with print residue turning the print white.
Comparing Prints
Despite technologya person still is needed todeclare a match.
Generally 8 – 14 points of similarity are needed toconsider 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 bylocal law enforcement agencies.