Date of Submission

2019

Document Type

Thesis

Degree Name

Master of Science in Forensic Science

Department

Forensic Science

Advisor

Virginia Maxwell

Committee Member

Alyssa Marsico

Committee Member

Kim Freeland

LCSH

Textile fibers--Microscopy, Textile fibers--Testing

Abstract

The analysis of fiber evidence involves the ability to link a questioned fiber back to its known source. But before the collection and analysis of questioned fibers, they could be potentially exposed to various environmental conditions for an extended period of time. There has been little research on how manufactured fibers are affected by various environments and if this interaction affects the ability to link a questioned fiber back to its known source. Changes to the manufactured fibers are essential to be aware of, in order to avoid the possibility of erroneous exclusions when performing fiber comparisons. A six-month time study was performed to determine how ten different environmental conditions would affect the physical, optical, and chemical properties of four manufactured fibers.

Fabric swatches of the nylon, acrylic, rayon, and polyester were exposed to solid conditions including sand, potting soil, chicken and cow manure and were also exposed to liquid conditions such as motor oil and winter road pretreatment fluids. Squares of each fabric type were placed in glass containers, each containing a different environment and stored for six months. Every two weeks fibers were subsampled from each environment and analyzed microscopically and instrumentally, using a bright-field and polarized light microscope, a Fourier-Transform Infrared Spectrometer, a Raman Spectrometer, and an UV-Visible Microspectrophotometer for fluorescence analysis. Comparisons back to the control fibers were used to determine if the fiber’s analytical data was measurably altered over time to a point where they were inconsistent with the known source.

Due to the increased strength and resilience of the manufactured fibers, there were no changes to the analytical data significant enough that the manufactured fibers could not be related back to their known source, except in the cases of complete degradation. Viscose rayon completely degraded in certain conditions but remained unaltered in others, while polyester remained unchanged in all conditions. The other fabric types, nylon and acrylic, were slightly altered but were still able to be related back to their known source. The only significant change that occurred, to all of the manufactured fibers, was the fiber’s fluorescence over time, but at this time the cause of these changes is uncertain. Further work needs to be conducted to determine the causes of the changes in fluorescence, but these results did not impact the fibers identification or inhibit the ability to link the fiber back to its known source. These results indicate that forensic fiber comparison analysis can be logically preformed on fibers that have been exposed to various environments, since the fiber’s structural, optical and physical properties remain stable over time.

Available for download on Saturday, May 13, 2023

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