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.