Date of Degree

6-2014

Document Type

Dissertation

Degree Name

Ph.D.

Program

Criminal Justice

Advisor

John A. Reffner

Subject Categories

Chemistry | Criminology | Criminology and Criminal Justice

Keywords

Dispersion, drug, fiber, mineral

Abstract

In developing countries like Thailand and in remote forensic laboratories around the world, scientific investigations of crimes are limited by the shortage of trained personnel and financial resources. The premise of this research is that polarized light microscope and dispersion staining methods will be developed which allow investigators with limited training to analyze physical evidence at a minimal cost. This research identifies specific liquids for the analysis of trace evidence using the dispersion staining technique. The development of dispersion staining technique and identification of specific liquid will extend the application of forensic science to remote laboratories and in the field to improve criminal investigations and justice. The methods developed in this research are fast, inexpensive and require minimum training; meeting the needs of developing countries and laboratories in the remote area. Dispersion staining is a non-destructive microscopical method that creates a uniquely colored image of a transparent sample when it is mounted in a specific liquid. This color is produced by differences between the refraction of light by the sample and surrounding liquid. The scientific principles of these techniques are well-established, but when applied to forensic science, they advance the capacity of developing countries to achieve high standards of evidentiary proof at lower cost. The collection of evidence, documentation of a crime scene and scientific examination of physical evidence are foundations of criminal investigation which both strengthen the prosecution and prevent wrongful convictions.

This technique can be used to detect, compare and identify very small particles. In this study, three classes of trace evidence were selected to demonstrate the practicality and advantages of this technique. The three classes are fibers, controlled drugs and soil minerals. Samples of each evidence class were analyzed in two steps: first, the Becke line method was used to observe and record the relative refractive index between a sample and mounting liquid, the second step was to put each sample in a specific refractive index liquid to generate distinct colors of the sample. The dispersion staining technique can differentiate and identify an unknown sample by the color produced in a liquid of a specific refractive index value. To validate the composition of exemplar evidence material, FTIR microprobe analysis was used. The rapid and reliable results of this method will aid criminal investigation in a remote area, improve law enforcement and reduce demands on central laboratory facilities.

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