Fingerprint Analysis

A fingerprint is the pattern of skin on the tip of each of your fingers. They form when pressure is applied to a child’s developing fingers before they are born. Fingerprints are extremely unique; there’s a one in sixty-four billion chance that your fingerprints match someone else’s. The chances of finding two like pairs of fingerprints are smaller than finding two like pairs of human DNA. Fingerprints date a few centuries back; they were used to signify trade and used for identification, but weren’t used for criminal means until the middle of the nineteenth century. During the late nineteenth century, in 1892, is the first record of fingerprints being used in a criminal investigation. This is when an Argentinian police officer utilized fingerprints in order to identify the murderer of two boys. When confronted with the evidence, the perpetrator confessed, marking the beginning of using fingerprints as evidence. In 1896, Sir Edward Henry established the Henry Classification System, by which fingerprints could be classified by their shape and distinguished among one another. Henry’s system soon became the primary system of use for the world. In 1901, the first ever Fingerprinting Bureau was established by Scotland Yard, soon followed by New York state prisons in 1903, and later, the FBI.

http://science.howstuffworks.com/fingerprinting3.htm


The act of lifting fingerprints plays a vital role in determining the possible suspects of a crime. There are three kinds of fingerprints: direct, latent, and plastic. Direct prints are fingerprints that are made after a person touches a surface after having come into contact with an easily visible substance, such as ink, paint, or blood. Latent prints are formed when fingerprints are made through the transfer of bodily fluids like sweat or oils. Lastly, plastic prints are developed when one’s fingers come into contact with a soft and/or porous surface. Direct prints are easily observed due to the ability to spot them visually. Conversely, latent or plastic prints are very difficult to find due to their being invisible to the unassisted eye.


When developing fingerprints on hard and nonabsorbent surfaces, like walls, glass, or tile/hardwood floors, the application of a powder to the prints is normally the most effective way of collecting them. When developing fingerprints on soft and/or porous surfaces, like cloth or paper, the application of a chemical is the most effective way to develop the prints. The color powder used to develop prints on hard surfaces depends on the color of the surface that the print is on. Dark powders such as carbon or charcoal powder are most effective on light colored surfaces, while a gray powder from aluminum is typically used for dark colored or mirror-like surfaces. Powders are applied using a brush, and stick to sweat and/or body oils in the fingerprint to make it easily visualized. The prints are then normally lifted with tape, because the powder will stick to the tape while maintaining the shape of the print.

Chemicals such as silver nitrate can be used to develop latent prints. After silver nitrate is applied, the fingerprint is developed by exposure to ultraviolet light. This occurs because of the reaction between the salt in one’s sweat and the silver nitrate, which form silver chloride, which is invisible. After a 3% solution is applied to the object containing the fingerprint and then exposed to ultraviolet light, a print will be shown in a rusty or black color. Then, investigators will most likely photograph the print for comparison to others.

http://www.bxscience.edu/publications/forensics/articles/fingerprinting/f-fing03.htm

There are three basic shapes of fingerprints. They include: arches, whorls, or loops. Arches look like a bump in the lines on your fingerprint. They can be gradual or steep. Whorls appear to be circles on your finger. They can be simple circles, or have a more sophisticated pattern. Loops look like waves in your fingerprint. Like whorls, they can be simple, or more intricate in nature.