Contributed by Susan Gross
Glitter can be considered an unusual type of trace evidence as compared to the traditional trace evidence of fibers, glass, hairs and paint. However, the popularity of the material on clothing, in cosmetics as well as art and craft supplies give this type of trace evidence more potential to be found than in the past. Glitter has been noted in various types of cases including assault, kidnapping, criminal vehicular operation and homicide. Although glitter cannot be individualized, it can associate a suspect with a victim, associate a suspect with a scene or indicate the seating position in a vehicle crash.
The general manufacturing process includes vacuum depositing metal onto a thin polymer film and coating it with a specific color. The different polymer types that have been reported include polyester, polyvinylchloride, and polypropylene. Cost and waste considerations have dictated the shape of glitter to some extent. Glitter also comes in a range of colors as well as it can differ in size and thickness. Variation in the layer sequence is another discriminating factor in glitter. The combined variation of class characteristics make glitter a type of trace evidence that can be very discriminating.
The first step in the forensic analysis scheme of glitter is to analyze the physical characteristics. Size, color, shape and layer structure can be discerning. Instrumental techniques such as Fourier Transform Infrared Spectroscopy (FTIR) can provide the polymer type as well as differentiate some samples. The colored layers can be compared using microspectrophotometry (MSP). In addition, the color layer as well as the metallic layer can be evaluated for elemental composition by a Scanning Electron Microscope with Energy Dispersive Spectroscopy (SEM/EDS). Lastly, different chemical solubility tests can be done but are recommended to be done last in the analytical scheme as they are destructive in nature. Solubility testing using phenol/chloroform/isoamyl alcohol, phenol/chloroform, and concentrated sulfuric acid have been reported.
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