Determination of the material’s distinctive characteristics based on the analysis of its unique properties is a constant task of the forensic expert. Glass analysis in forensic science consists of comparing several fragments to establish their source. At the moment, only a comparison of the physical properties of glass makes it possible to conduct this procedure. After identifying the material as glass using microscopic examination, simple physical properties such as shape, color, thickness, and texture are described (Siegel and Mirakovits 441). There is a chance that these measurements would be enough to exclude the possibility of fragments originating from a specific source. Otherwise, it is necessary to conduct a more detailed analysis.
Density and refractive index are the most critical parameters. Density matters because it does not change depending on the size of the fragment. The floatation method is usually used to measure the property (Siegel and Mirakovits 446). The technique of such measurements consists of immersing the glass in a liquid of a specific density. The glass will be finally suspended in the same density liquid, and then the measurements can be recorded. For determining the refractive index, a microscope equipped with a hot stage is usually used. The glass is immersed in oil with a specific refractive index. The oil is then heated, which changes the index until the glass is no longer visible. With the help of such procedures, more accurate data on the physical properties is obtained.
The methods are used to fulfill their function, but the physical properties determination is not always sufficient to establish the belonging of the glass to a specific source. The same refractive index and density do not guarantee the identity of two two glass fragments, only the probability (Siegel and Mirakovits 450). This is because different types of glass can be common. In such cases, it is necessary to pay attention to additional signs of a specific glass fragment, such as glue, paint, cover among others. In more complicated situations, chemical analysis is used, but this rarely happens due to the process’s high cost and complexity. Most often, the first stage of describing the simple physical properties of glass is sufficient to determine the source.
Work Cited
Siegel, Jay A., and Kathy Mirakovits. Forensic Science: The Basics. 2nd ed, CRC Press, 2016.