The Utilization of Microscopy in Developing Investigative Leads from the Examination of Microscopic Trace Evidence in Forensic Investigations

Abstract

The majority of trace evidence examinations, performed in laboratories of forensic science throughout the world, are of a comparative nature. Questioned (Q) items of evidence (e.g., fibers, hair, glass, paint, soil) from a crime scene (or victim, suspect, location, etc.) are compared to suspected items of known (K) origin to determine the likelihood that the K and Q items could have originated from the same source. The justification normally invoked for performing these comparisons is Locard's Exchange Principle, which states that whenever two objects come into contact there is a transfer of material between them. The original research into the analysis of dust traces, which led Nickolls 1 in 1956 to recognize and name this principle, was performed by Edmond Locard between 1910 and 1965. Since then, this principle has been repeatedly validated by means of published research and casework. The research reports describe the results of transfer experiments, most often with fibers, performed by forensic scientists from around the world. The results of these experiments have all confirmed Locard's original premise. Published casework reports also confirm the utility and value of microscopic traces in demonstrating contact between individuals, vehicles, sites, etc., to events in question, even when no eye witnesses were present to give testimony.

Damage characteristics of fabrics created by TASER probes

“…This experiment agreed with this theory since polyester samples displayed more fused yarn ends compared to cotton samples. Nevertheless, there was melting on the cotton samples in this experiment and there were deformations on the fiber ends that have an appearance similar to the melting phenomenon described in the previous research [7,8]. It is likely due to the fact that the previous research was done by using firearms and there was a higher amount of heat transmitted to the fabrics, and the melting in this experiment was caused by electrical energy which made the differences.…”

“…The feature of damages by TASER devices present on these three levels may vary for different types of fabrics due to their distinct properties. Cotton fibers are considered to be natural and are cellulosic fiber, while polyester is a type of synthetic fiber, and the blend is a mixture of them [7,8]. Polyester consists of filaments that are fibers of indefinite length, while cotton is sorted as staple fibers that are shorter in length and easier to disturb [6].…”

“…Therefore, it was expected that damage on fabrics that contain cotton fibers would have relatively frayed yarn ends and polyester would have relatively neat yarn ends. When the probes are fired and touch the fabric, the electrical energy, and kinetic energy from the probe movement will partially transfer to the fibers and create tensions that could break the fibers [7]. The thermoplastic polymers in synthetic fibers (like nylon and polyester) could melt due to the energy transfer, while the natural fibers like cotton will not melt [7,8].…”

“…When the probes are fired and touch the fabric, the electrical energy, and kinetic energy from the probe movement will partially transfer to the fibers and create tensions that could break the fibers [7]. The thermoplastic polymers in synthetic fibers (like nylon and polyester) could melt due to the energy transfer, while the natural fibers like cotton will not melt [7,8]. Therefore, fiber deformation such as mushroom-shaped morphology caused by the melting of fiber ends is expected to be present in both polyester fabrics and blend fabrics and absent in the cotton fabrics [8].…”

Tracking the Route Walked by Missing Persons and Fugitives: A Geoforensics Casework (Italy)

“…Comparative analyses and provenance studies, based on mineralogical, petrographic, sedimentological, paleontological, and geochemical investigations [38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54]. Forensic comparisons between two or multiple samples of geological and soil traces and microtraces are aimed to ascertain whether they originated from different sources [51].…”