Fiber evidence

Miller, C.L., Day, T.A., Bennett, J.L. and Rax, R.A. (1996) Schistosoma mansoni L glutamate-induced contractions in isolated muscle fibers evidence for a glutamate transporter. Experimental Parasitology 84, 410—41 9. 

Lee, I., Evans, B. R., and Woodward, J., The mechanism of cellulase action on cotton fibers Evidence from atomic force microscopy. Ultramicroscopy 2000, 82 (1-4), 213-221. 

It is known since time that stretching before (Prescott and Ott ) and/or during (Johnson et al. ) the stabilization treatment improves the mechanical properties of the resulting carbon fiber. Evidently, high molecular order is required. If such order has been obtained in the spinning process by extensive stretching, care must be taken... 

Fiber Evidence. Because analyses reveal no organic structure, the fiber evidence is of physical rather than chemical nature. As noted earlier, the yarn-type formations consist of paired hair-like strands moving parallel to each other (Figure 6). Two hair-like strands are used consistently in each unit, and the strands do not twist around each other. Rather they maintain the same plane or axis. In addition, each formation follows a trajectory that, although following the contours of the blade, is relatively straight. No crimp or waviness was observed. 

Haines DE, Rubertone JA (1977) Cerebellar corticonuclear fibers evidence of zones in the primate anterior lobe. Neurosci Lett., 6, 231-236. 

Boucek RJ Jr, Buck SH, Scott F, Oquist NL, Fleischer S, Olson RD (1993) Anthracycline-induced tension in permeabilized cardiac fibers evidence for the activation of the calcium release channel of sarcoplasmic reticulum. J Mol Cell Cardiol 25 249-259... 

In cases of sexual assault and homicide, the transfer of single fibers often have important forensic significance. The case that most significantly impacted the realization of the importance of fiber evidence was the Atlanta murders that occurred between 1979 and 1981 (33,34). The bodies of 28 boys and young men were foimd under similar conditions. Although many of the bodies contained fiber and hair evidence that compared closely, Wasuie Williams was prosecuted and convicted for only two of the homicides. The conviction was based solely on multiple transferred hairs and fibers with an emphasis on imcommon carpet fiber found in the bedroom of Williams s home. 

Synthetic fibers are abundant in sludge, sludge products, and sewage treatment plant effluents. The fibers evidently are introduced from clothes-washing machines and survive the sewage treatment process. 

From Deadman, H. A. "Case Reading Fiber Evidence and the Wayne Williams Trial," in R. Saferstein, ed.. Criminalistics An Introduction to Forensic Science. Upper Saddle River, NJ Prentice-Hall, 2004. 

Houck, M. "Inter-comparison of Unrelated Fiber Evidence." Forensic Science International 135 (2003), 146-149. 

Fibers—specifically, textile fibers—are common forms of transfer and trace evidence and are arguably the largest category of polymer evidence anal) zed in forensic laboratories. Fibers are amenable to analysis with nearly ev ery kx)l available to the forensic chemist, from optical instruments and PLM to microspectrophotometry and chromatography. As the arsenal of anal)dical tools available grows, fiber evidence is getting renewed interest from forensic chemists and hace evidence analysts. 

Figure 14.26 illustrates the three modes of IR as applied to fiber evidence. The transmission mode is implemented on a fiber placed in the path of the beam, either by suspension across the sampling gap in the stage or with the fiber mounted cm a KBr pellet. Adhesive tape is often used to hold the fiber in place. For... 

Continuing with the example of a dumped body, the fibers associated with that body reflect its most recent environment. Unlike a stain, fiber evidence is transitory, and as more time passes since the time of transfer, the more fibers are lost. The body will carry with it evidence of the environment, including the dump site, in which the person spent the last hours of life. Absent unusual treatment, the decay of fibers on a substrate approximates a first-order decay curve. Consequently, fiber evidence is perishable evidence yet, while any one fiber may not be particularly telling, the combination often is, as it was in the Williams case. 

Laboratories and analysts allocate their time and effort to those areas which appear most promising. On the basis of the preceding discussion, it should not be surprising that some types of fiber evidence are deemed too common to be of evidentiary value. A 2001 survey revealed that about half the responding laboratories in the United States and Europe did not routinely examine undyed cotton fibers. Blue denim is not routinely analyzed in 20% of U.S., and nearly 50% of European, laboratories. The decision to analyze or not to analyze a particular kind of fiber is based on knowledge of the background environmental level of the fiber. 

The identification and comparison of fiber evidence in the forensic laboratory can encompass a number of different techniques. Nondestructive examination of fibers by polarized light microscopy, microspectrophotometry, and PT IR spectroscopy very often provide a sufficiently high discrimination in most casework comparisons that other analytical tests are not needed. When a sufficient amount of fiber evidence exists, a comparison of fiber dyes by thin-layer chromatography (TLC) or HPLC will often further the discrimination. Auxiliary techniques such as PGC, PGC/MS, pyrolysis mass spectrometry (PMS), and SEM-EDXS are only sporadically used when the evidence or situation is required. 

PGC has been applied to the characterization of a number of different types of polymers besides the traditional paint chips and fiber evidence submitted to the crime laboratory. Synthetic plastics have been readily identified and differentiated by PGC (253). Hume et al. (265) applied PGC to the characterization of motor vehicle body fillers utilizing a 15-m Carbowax 20 M gas chromatographic column and a computer-based system to compare pyrograms. 

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