Trace Evidence: Proper Collection, Preservation, and Analysis

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Glass

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 information, in conjunction with other evidence, can assist investigators in determining what occurred at a scene and identify individuals who were at the scene.

Collection and Preservation

Every possible piece of broken glass should be collected from a crime scene if any chance of piecing it back together exists (Saferstein, 2009). A sample piece from an identifiable source should be collected for comparison purposes. For example, at a vehicle accident scene with broken headlights and windows, sample glass should be taken from any glass remaining in the window frame and headlights to assist in identifying pieces of glass collected at the scene. Glass samples should be placed in solid containers to prevent further breakage of the sample (Saferstein, 2009). All samples should be clearly labeled identifying point of origin. Interior and exterior sides of the glass should be labeled if known. When broken glass is on cloth the entire piece of cloth should be collected. The cloth should be preser...

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