Understanding the Effects of Environmental Exposure on Fiber Comparisons

The samples brought in to crime labs for analysis are rarely ever in pristine condition. Wear and tear through exposure to environmental and other factors can sometimes make it very difficult in cases where a significant length of time has transpired between collection of a known and unknown sample. This can affect the chemical and physical properties of the fibers, making it hard to compare these samples and make a determination about their potential origin. The STG has discussed this matter with several forensic examiners, and are beginning to explore the effects of different environmental conditions have on different commonly found fiber materials. The role of temperature, humidity, and UV light will be the first conditions to be assessed. Using a suite of analytical techniques, including those available to crime labs and some others, we are exploring any chemical and physical changes that occur to the fibers as a function of condition and time. We hope to be able to provide the forensic community with guidelines for what changes are observed when the fibers are exposed to different conditions so that they can better assess trace samples when they are presented with them as forensic evidence.