FINGERPRINTS
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 identified.
Dactyloscopy is the study of fingerprint identification. Ridgeology: The study of the uniqueness of friction ridge structures and their use for personal identification.1 minutiae points: points where the ridge structure changes.
Ridge Characteristics Use these characteristics as points of identification when comparing fingerprint samples. The more points you can find in common, the better the match!
Ridge Characteristics Crossover Core Bifurcation (fork) Ridge ending Island Delta Pore Scar EXAMPLE http://cnx.org/content/m12574/latest/properties.jpg
How many ridge characteristics can you identify in this fingerprint? http://www.dkfz.de/tbi/projects/bmcv/images/iu_it246_04s_fingerprint1.jpg
Fingerprint- An impression left on a surface by the ridges on a finger Latent fingerprint-hidden finger prints made visible by treating with a powder. Patent fingerprints-The transfer of a fingerprint pattern by blood, ink or another substance. Plastic fingerprints- indentations left in soft material such as clay or wax.
3 types of patterns Arch- ridge pattern that originates from one side of the finger and leaves from the other (5%) Whorl- fingerprint that resembles a bull’s-eye (30%) Loop- Pattern flows inwards and returns to the area it started. (65%)
CHARACTERISTICS OF FINGERPRINTS
Core- the center of a loop or whorl Delta- triangular shaped area near a loop Ridge count- the number of ridges between the core and a delta on a finger print.
5 Steps For Fingerprinting Clean finger tips with alcohol Individual stands in front at an arms length away Roll the finger from one side of the nail to the other on the ink pad. Ink should cover up to the first joint of the finger Place the finger on the appropriate space and gently roll the finger from one side of the nail to the other. Make note of any deformations or missing fingers.
Ten card – form used to preserve a persons fingerprints.
Collecting Fingerprints
Prints may be collected by revealing them with a dusting of black powder and then lifted with a piece of clear tape. Did you know? Camel hair is the most common animal hair used to make fingerprint brushes. Now many brushes (like the one above) are made out of fiberglass.
Some investigators use fluorescent powder and UV lights to help them find latent prints on multi-colored or dark surfaces. Magnetic powder can also be used to reveal latent prints. This type of powder works better on shiny surfaces or plastic baggies or containers.
The cyanoacrylate fuming method (often called the super glue method) is a procedure that is used to develop latent fingerprints on a variety of objects. Ninhydrin is a chemical that bonds with the amino acids in fingerprints and will produce a blue or purple color. It is used to lift prints from surfaces such as paper and cardboard.
CHANGING FINGERPRINTS There are several documented cases of people deliberately mutilating their fingerprints in an effort to avoid being identified from marks left on the surfaces they touch. Methods used have included burning the fingertips with acid, which John Dillinger tried, and surgical alteration.