Trace Evidence: Proper Collection, Preservation, and Analysis

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Importance of Glass Trace Evidence Unique characteristics and properties of glass may provide valuable information to investigators. Glass is made of materials having no definite form on their own melted together and cooled to rigidity without crystallization (“Glass”, 2011). Glass can be made in varying thicknesses, colors, and with patterns and designs or smooth. Glass may be produced in a manner that reduces or prevents shattering, resulting in small pieces rather than slivers or fine powder-like pieces (Saferstein, 2009). The density and refractive index of glass fragments can be used to determine if the fragments originated from a single source item, such as a broken window on a home, or from various items. The
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The sharp edges of broken glass can easily cut the evidence collector, and the blood contaminates the evidence. Because broken glass may be a fine powder-like substance the evidence collector should also wear a mask covering the mouth and nose. Eye protection is also recommended.
Identification and Analysis Analyzing glass is a complex process. The properties of glass are found and measured to enable forensic scientists to identify glass from the same source or to eliminate sources ( Saferstein, 2009). Complete reconstruction of glass fragments is rarely possible due to glass often shattering into a fine powder-like substance. When complete reconstruction is possible though the glass can be identified as coming from a single source item. When all the glass fragments from a scene can be pieced together the glass can be identified as coming from a single source item. Additionally, because glass is manufactured on a large scale identification from a single source of manufacture is extremely difficult (Saferstein, 2009). Glass can be identified as belonging to a specific item, such as a headlight, but identification of the make and model of vehicle is nearly impossible. Glass fragments can be identified as originating from a single item or multiple items. The distinction is characterized as class
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