Fiber Impurities Allow for Forensic Fluorescence Comparisons

• NCJ Number: 251601
• Date Published: April 2018
• Length: 2 pages
• Grant Number(s): 2011-DN-BX-K553
• Agencies: NIJ
• Publication Type: Research (Applied/Empirical); Report (Study/Research); Report (Grant Sponsored); Program/Project Description; Factsheet
• Award: Comparison of Microspectrophotometry and Room-Temperature Fluorescence Excitation-Emission Matrix Spectroscopy for Non-Destructive Forensic Fiber Examination

Annotation

This fact sheet summarizes a report on new analytical procedures that produce fiber comparisons more detailed than those produced by standard forensic practices.

Abstract

This research determined that by acquiring excitation-emission matrixes (EEM) that are typically screened out with band-pass filters, valuable identification information on single fibers can be obtained. Although fluorescence microscopy is commonly used by forensic labs to examine fibers, the researchers in the current project determined that by removing specific signal filters from their instruments, they have "taken the non-destructive nature of fluorescence microscopy to a higher level of selectivity." They concluded that when the usual filters are in place, forensic investigators cannot record excitation and emission spectra from their fluorescence microscopes. Consequently, the information they can obtain on the spectral features of textile fibers is limited. The instrumentation recommended from this project removes this limitation by coupling a microscope to a spectrofluorimeter. This procedure examined not only impurities embedded into fibers during the fabrication of garments, but also at the spectral changes that can occur in textile fibers due to exposure to environmental conditions such as laundering, cigarette smoke, and weathering. The project collected visible absorption spectra from three pairs of dyed fabrics. Each pair contained dyes with highly similar chemical structures. Beyond identifying impurities in textile fiber, the recommended procedure determined whether a fiber had been washed. Also, the effects of weathering on the spectral signals from fibers varied with the types of fiber. Researchers recommend that future studies compare fibers from humid environments compared to desert environments. 1 figure