Date of Degree

6-2022

Document Type

Dissertation

Degree Name

Ph.D.

Program

Criminal Justice

Advisor

Thomas A. Kubic

Committee Members

Nicholas D. K. Petraco

Nicholas Petraco

John R. Lombardi

Subject Categories

Physical Sciences and Mathematics

Keywords

forensic science, minerals, Electron Backscatter Diffraction, Scanning Electron Microscopy, Energy Dispersive Spectroscopy

Abstract

Electron Backscatter Diffraction has been largely used in the metallurgic and material sciences and until now, has found few applications in the forensic sciences. One of the few utilizations of this technique in forensic science is in firearm serial number restoration as a complementary technique to the time-consuming and tedious chemical etching methods. This research aims to expand the uses of Electron Backscatter Diffraction in the forensic sciences as it applies to other types of samples, specifically as it pertains to forensic mineral analysis.

Electron Backscatter Diffraction offers the analyst information regarding crystal structure of a material, so long as the sample is crystalline in nature. Minerals, many of which are crystalline in nature, can be analyzed using Electron Backscatter Diffraction. The Electron Backscatter Diffraction instrumentation used to achieve these patterns is coupled with a Scanning Electron Microscope and Energy Dispersive X-ray Spectrometer. These three instruments provide the analyst information of morphology, elemental composition, and of course, crystal structure. This combination of information in one single system is the most attractive feature of this method.

Minerals have long been encountered in items of forensic importance, primarily as the main constituent of the inorganic portion of soil. Scientists have determined numerous methods to analyze this type of evidence by its mineral content, to determine if two samples came from a common origin. This information can aid in a forensic investigation to determine if a suspect has ever been at a crime scene, or with the use of geo-sourcing, determine where a crime scene is located.

Polymorphisms are of special importance in forensic science as they further allow the differentiation of samples based on their crystal structure. By many of the currently used forensic techniques for analyzing the mineral fraction of soil samples, only the chemical composition is determined, by the physical properties of the bulk sample assessed. However, with the use of Electron Backscatter Diffraction, one can determine the crystal structure and determine the polymorph present. Determining the crystal structure of a mineral can help to add to the information about a sample, either as exclusionary or inclusionary evidence in a forensic investigation.

This study aims to examine minerals commonly found in nature, which could ultimately become forensic evidence, and the ability of Electron Backscatter Diffraction to obtain crystal information from a single grain or crystal. The parameters necessary to achieve this information will be thoroughly studied. Various sample preparation techniques will be considered. The applicability of this technique to gem authentication will be tested. Lastly, this research aims to answer the question as to whether Electron Backscatter Diffraction can be successfully used to analyze minerals in real forensic case samples.

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