JS 112 Handout fingerprint

JS 112 Handout fingerprint - JS 112- Fingerprint Laboratory...

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JS 112- Fingerprint Laboratory Fingerprinting Laboratory Fingerprints are a very common form of physical evidence. It requires considerable expertise in the area of fingerprinting to be able to accurately classify prints and match prints with each other. If a suspect’s fingerprints match those found at a crime scene, this is highly conclusive proof of a link between the two. In this lab exercise, you will not attempt to classify fingerprints. Rather, you will investigate the methods used in developing and lifting latent fingerprints from a number of objects, made of a variety of materials. Latent prints are those invisible prints left on an object by a person. These must be developed through the use of dusting powder or a chemical solution. Inked prints are those taken directly from a person’s fingers through the use of an inkpad or block. The origin of the use of fingerprints is lost in history, although it is known that the Chinese knew of and used fingerprints before the birth of Christ. In 1886, a Scottish physician, Henry Fauld, first published the view that fingerprints could be used for identifying individuals. We owe the beginnings of our present system to Sir Francis Galton in the 1880s. Sir Edward Richard Henry developed a simplified system for classifying fingerprints, which was adopted by Scotland Yard in 1901. There are a number of basic fingerprint patterns: loops, arches and whorls (LAW). The fingers on a person’s hand may contain a number of patterns. You should make yourself familiar with the characteristic appearance of each of the patterns, as you will be making comparisons with these patterns in this lab exercise. The tips of a person’s fingers have small friction ridges on them. These ridges are formed during embryological development are unique to every individual and remain unchanged until post mortem decay. Along these ridges are small pores which secrete salt (NaCl), water and proteins. It is those substances, along with oil that may be picked up by touching the hairy portions of the body, which will be deposited on objects that come in contact with the surface of our fingers. Usually, burglaries and other crimes are committed during times when a building or room is dark. In feeling his/her way around an unfamiliar setting, the person committing the crime may touch several objects. Invisible latent prints are then left in many places. It requires some time to dust and lift these prints. An experienced person is required for this task, as poor dusting technique may ruin a very good print. As such we have left the syringe evidence to be processed by an expert however, we will conduct developing and lifting on our own prints so you can have a hands- on appreciation for fingerprint detection and development.
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JS 112 Handout fingerprint - JS 112- Fingerprint Laboratory...

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