Hair Fiber Rev 3

Hair Fiber Rev 3 - Experiment 7.2 Microscopic Examination...

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Experiment 7.2: Microscopic Examination of Hairs and Fibers Introduction Microscopic examination of evidence collected at a crime scene can often lead to the discovery of important information. Ideally, these microscopic studies can show a unique link between the evidence collected at the crime scene with materials obtained from a suspect or their possessions. It is difficult to refute the connection between these materials if microscopic individual features can be found. " The 'matching' fibers were taken only from victims," he says. "Only one individual red cotton fiber was found at the Williams home — which can be found in abundance at K-Mart or Walmart — which is similar to fibers in victim Michael McIntosh's underwear. That came from the vacuum sweepings of a car, which the Williamses may or may not have owned at the time that McIntosh was murdered. Not one fiber from any victim was found anywhere near the carpet in the Williams' house "Insofar as the Wellman fiber is concerned, they were attempting to demonstrate how rare the fiber in the carpet in 'Wayne Williams' room' was. This ignores the fact that all of the Williamses, and any regular visitor to the home, existed in the same environment." ( By Marilyn Bardsley and Rachael Bell Microscopic evidence examination can include materials from both inorganic and biological sources. Such samples may include soils and minerals, bullet casings, scratch marks, and hair and fiber samples. Hair and fiber sample are particularly useful in linking crime scene evidence and potential suspects and have successfully be employed in many investigations. Objectives In this lab you will examine a variety of hair and fiber samples. The goal will be to understand the variations of hair samples both between species and within species. In addition, typical fiber samples will be examined to learn more about how they are microscopically identified. Background The examination of human hairs in the forensic laboratory is typically conducted through the use of light microscopy. This examination routinely involves a two-step process - the identification of questioned hairs (usually species or origin) and the comparison of questioned and known hairs. The purpose for conducting this examination is to learn whether two fibers had a common origin or whether an individual(s) could have come into contact with a particular object. This associative evidence is particularly useful in crimes of violence, such as homicide, sexual assault, and aggravated assault, where physical contact may have occurred. Crimes such as burglary and armed robbery typically involve the recovery of debris and articles of clothing which may contain hairs Hairs and Fibers 1 Copyright 2011 Figure 1 . Colored scanning electron micrograph (SEM) of hair shafts growing from the surface of human skin ( , Image P720/255).
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and fibers useful for the identification of suspects. Humans constantly shed hairs that can be distributed in a crime scene, on a victim or on
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Hair Fiber Rev 3 - Experiment 7.2 Microscopic Examination...

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