Fingerprinting Information Sheet

Transcription

1 Fingerprinting Information Sheet HISTORY Fingerprints weren t always used as a means to identify criminals. One of the first methods used to compare physical characteristics was developed in 1883 by Alphonse Bertillion and was called anthropometry and later came to be known as BERTILLIONAGE. This system involved taking hundreds of measurements of different body parts and noting any identifying marks such as tattoos or scars. All these measurements and details were recorded on a card for the individual. The system relied heavily on police officers to take the measurements in exactly the same manner and could be subject to variance from one officer to the next. Sir Francis Galton, a British anthropologist and a cousin of Charles Darwin, began his observations of fingerprints as a means of identification in the 1880s. In 1892, Sir Francis Galton published his book Fingerprints. This tome highlighted the uniqueness of prints and included a systematic approach to using prints to identify people. The book included the first classification system for fingerprints. Galton s Details were included in the classification system and formed the basis for what are now known as minutiae, which are still used in classifying and identifying fingerprints. Interestingly, Galton hoped to use fingerprints to identify the race and intelligence of individuals. While there is no connection between fingerprints and these traits, his research laid the foundation for dactylology. (Dactylology is the study of fingerprints.) He demonstrated that fingerprints do not change over the course of an individual s lifetime and that no two fingerprints are exactly the same. According to his calculations the odds of two individual fingerprints being the same were 1 in 64 billion. Both Bertillionage and Galton s Details were used to identify individuals. Each police division used whatever method they preferred. It wasn t until the case of Will and William West that fingerprinting became the preferred and recommended method used to identify suspects. Will and William West were inmates at Ft. Leavenworth prison; and in 1903 the two, unrelated men could not be distinguished from one another using anthropometry. However, it was discovered that they had unique fingerprints. Once this case gained public attention, the use of fingerprints spread. Today, fingerprints are used as a primary means of identifying suspects and linking them to crime scenes and crimes.

2 FORMATION Each fingerprint is an INDIVIDUAL CHARACTERISTIC and no two are alike. No two have yet been found to possess identical characteristics. Fingerprints are the product of your genes as well as the environment of the womb during development in the first trimester. Things like nutrition, blood pressure, and physical contact with the womb affect fingerprint development. Once they are developed fingerprints do not change over the course of your life. They may be altered or scarred. Your skin is composed of layers of cells. The epidermis is the outer layer, while the inner layer is called the dermis. In a cross section of skin there is a boundary of cells separating the dermis and epidermis. This boundary is made up of dermal papillae. These cells determine the form and pattern of ridge patterns. Dermal Papillae are formed in fetus and remain unchanged during life. Sweat glands discharge and deposit perspiration to the surface of the skin. Sweat is vital to the formation of latent fingerprints. LATENT PRINTS Each skin ridge is populated with a single row of pores openings for ducts leading from sweat glands. There are two types of sweat glands only those found on the surfaces of the hands and feet (eccrine glands) secrete perspiration that does not contain oil. Any oil in fingerprints comes from the hand contacting other parts of the body (e.g. face) or other substances containing oil. Perspiration from eccrine glands discharges and deposits water, urea, salts, and proteins on the surface of the skin. When the finger comes into contact with another surface, the water and dissolved substances are transferred. This leaves an impression of the finger s ridge pattern (fingerprint). These are typically invisible to the eye and referred to as latent fingerprints. Patent prints are fingerprints which are visible to the naked eye. These types of prints are typically more oil based. FINGERPRINT PRECIPLES A fingerprint is an individual characteristic; no two people have been found with the exact same fingerprint pattern. NOT EVEN IDENTICAL TWINS! A fingerprint pattern remains unchanged for the life of an individual, however, the itself may change due to scars or skin diseases. Fingerprints have general characteristic ridge patterns that allow them to be systematically identified.

3 Fingerprint Classes Arch: 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. Plain Arch: Ridges enter on one side and exit on the other side. Tented Arch: Similar to the plain arch, but has a spike in the center; inside angle is smaller than 90 degrees. Both types of arches comprise about 6% of all fingerprint patterns. Loop: 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. Loops come in, curve, and go back out the same side, usually curing around a delta. Ulnar loops: Ridges flow from and curve toward the little finger (or ulnar side). Son on the right hand, a loop that opens toward right or the ulna bone is an ulnar loop. While on the left hand a loop that opens toward the left would be an ulnar loop. Ulnar loops are about 60% of fingerprints. Radial loops: Ridges flow from the curve toward the thumb side (or radial side) of the hand. So on the right hand a loop that opens toward the left or the radial bone on the right hand is a radial loop. While on the left hand a loop that opens toward the right would we a radial loop. Radial loops are approximately 5% of fingerprints. Double loops: Two separate loops are present and sometimes surround each other. Accidental loops: Any pattern which does not conform to any of the previous patterns. Whorl: 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: At least two delta type divergences are present with curving ridges in front of each other. Whorls comprise approximately 29% of all fingerprint patterns. Central Pocket Whorl: Some ridges forma a loop pattern which curce and surrounds a central whorl with one delta. Double-loop Whorl: Double loop whorls are made up of any two loops combined into one print. Accidental Whorl: Accidental whorls contain two or more patterns (not including the plain arch) or do not clearly fall under any of the other catergories.

4 PATTERNS Dermatoglyphics Individuality is not determined by general shape or pattern but by a careful study of its ridge characteristics also known as minutiae. Identity = number and relative location of features that impart individuality. The features should be in the same relative location to one another. In court, a point-by-point comparison must be made to establish identity.

5 MINUTIAE RIDGE ENDING BIFURCATION LAKE DOT or ISLAND INDEPENDENT RIDGE SPUR BRIDGE Minutiae alone do not individualize a print the location of and type of minutia make each fingerprint unique. There has never been two fingerprints found that have the exact same minutia in the exact same place. So, if you are comparing prints say from a suspect and a crime scene and the prints have the same minutiae in the same location, you can deduce that they are from the same person. There are as many as 150 individual ridge characteristics on the average fingerprint. a vast majority of prints recovered from crime scenes are partial impressions- showing only a segment of the print.

6 Experts have to compare a small number of ridge characteristics from the recovered print to the known recorded print. Criteria of individuality in court generally requires 8-16 matching characteristics, but often this number is not as important as the expertise of the fingerprint examiner International Association for Identification concluded, It is the responsibility of the examiner- based upon experience and knowledge to establish positive identification.