Trace evidence analysis in forensic science

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*Corresponding author: Bandr Fakia ISSN: 0976-3031

Research Article

TRACE EVIDENCE ANALYSIS IN FORENSIC SCIENCE

Bandr Fakia*

Department of Medical Health services Faculty of Health Sciences Umm Al-Qura University, K.S.A.

DOI: http://dx.doi.org/10.24327/ijrsr.2018.0910.2851

ARTICLE INFO ABSTRACT

New technologies have emerged in forensic science and their application in solving trace evidence problems is intended to solve some of the limitations encountered when solving specific analytical problems. This article proposes that in cases where thermal spray painted objects are suspected to have been involved in the course of a crime, surfaces of objects with thermal spray painted coatings should be tested for the presence of trace materials because this approach will offer valuable clues during the investigation process. Different trace materials attach themselves on different surfaces based on the features on the surfaces of trace materials. Also, the features of the surface onto which the trace material will be attached affect the adhesivity of trace materials. This article proposes that there should be research on the way different trace materials are attached on thermal spray coatings based on the hardness, density, and porosity of the coatings. The article proposes that adhesion of surface materials will affect the ability of trace materials to be attached to the surface of thermal spray paints. The article also proposes that collecting trace evidence on surfaces of thermal spray paint coatings.

INTRODUCTION

Roux et al (2015) defined trace evidence as the surviving evidence from a former action or occurrence of an agent or event (Roux, Talbot-Wright, Robertson, Crispino, & Ribaux, 2015). These scholars further define trace evidence as a very small amount of substance that is too minute to be measured (Roux, Talbot-Wright, Robertson, Crispino, & Ribaux, 2015). Hence, trace evidence can be defined as the analysis of materials that, due to their texture or size, transfer from one place to another and persist in these new locations over an extensive period of time (Roux, Talbot-Wright, Robertson, Crispino, & Ribaux, 2015). Examples of trace materials include building materials, hair, and fabric and textile fibers. Bhatia (1999) defines spray painting as a process that involves a group of processes wherein a feedstock material is heated and propelled as individual particles or droplets onto a surface (Bhatia, 1999). Basically, the applied coating has characteristics that depend on the feedstock material, procedures and application parameters used in thermal spraying, and subsequent treatment of the coating (Bhatia, 1999). This paper proposes that characteristics of thermal coat paintings, types of thermal spray paintings, and thermal spray processes affect the ability of the spray painted surface to pick

up and deposit trace evidence materials such as spores, pollen grains, human and animal hair, and soil particles from a crime scene. Thus, spray painted materials that are suspected to be involved in a crime should also be analyzed for clues during forensic investigations.

Problem Statement

New technologies have emerged in forensic science and their application in solving trace evidence problems is intended to solve some of the limitations encountered when solving specific analytical problems (Stoney & Stoney, 2015). The first approach (general practitioner’s approach) is flawed because it focuses on a broad assemblage of various particle types (Stoney & Stoney, 2015). The second approach focuses on one specific particle type (Stoney & Stoney, 2015). However, both methods have flaws that necessitate the need for a new third approach that will be more effective in using available trace evidence to solve forensic cases (Stoney & Stoney, 2015). This new method should be created through rethinking current forensic paradigms based on specialisms, revisiting the basic principle of forensic science, and adapting these principles to the context of the 21st century (Roux, Talbot-Wright, Robertson, Crispino, & Ribaux, 2015). In cases involving objects that have been thermally sprayed, understanding the

International Journal of

Recent Scientific

Research

International Journal of Recent Scientific Research

Vol. 9, Issue, 10(E), pp. 29381-29385, October, 2018

Copyright © Bandr Fakia, 2018, this is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution and reproduction in any medium, provided the original work is properly cited.

DOI: 10.24327/IJRSR

CODEN: IJRSFP (USA)

Article History: Received 4th July, 2018 Received in revised form 25th August, 2018

Accepted 18th September, 2018 Published online 28th October, 2018

Key Words:

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effect of different materials on the surface of the coated object can help in solving forensic cases. Hairs, soil particles, and palynomorphs present in a crime scene can be used to identify the vehicles and any other spray painted objects that may have been involved in the crime. Also, some particles from a spray painted object can be deposited in a crime scene and the features of these particles can be used to identify suspects. Hence, this article will describe different trace materials and the thermal spraying process, and, where possible, offer suggestions on how forensic science can combine available knowledge on the two fields to improve the quality and reliability of forensic investigations.

Trace Evidence Analysis Approach

Different trace materials attach themselves on different surfaces based on the features on the surfaces of trace materials (Raymond, Dunn, & Li, 1999). The surface of thermal spray paint coatings is affected by materials used, spray paint processes, and application parameters (Bhatia, 1999). This article proposes that in cases where thermal spray painted objects are suspected to have been involved in the course of a crime, surfaces of objects with thermal spray painted coatings should be tested for the presence of trace materials because this approach will offer valuable clues during the investigation process. Stoney and Stoney (2015), came up with seven characteristics of effective trace evidence analysis approach. First, trace particles should be used as a major tool for solving problems within the fields of forensic science (Stoney & Stoney, 2015). This article proposes that evidence from trace materials and knowledge of spray painted surfaces can be used in investigations. Secondly, the methods that forensic scientists use to enable their application should be straightforward and readily available (Stoney & Stoney, 2015). The third characteristic is that all potentially useful and available particle types should be considered (Stoney & Stoney, 2015). In the proposed method, all possible identities of trace materials have been considered. Traditional methods ignored trace evidence from spray painted materials and the proposed method seeks to solve this error.

In addition to this, the decisions to use potentially useful and available particle types should be guided by the contribution and efficiency of the approach (Stoney & Stoney, 2015). The proposed approach of trace evidence analysis identifies that trace materials from spray painted surfaces can contribute to the corpus of available evidence and is thus effective in solving crimes. The other characteristic is that all types of analysis should be performed with appropriate technologies (Stoney & Stoney, 2015). In this proposed method, all appropriate technologies for analyzing trace evidence are not used separately but are rather combined to improve the reliability of the research. Another characteristic is that the findings must be timely and should enable the forensic scientists to integrate the evidence with case specific problems. In this case, available trace evidence from palynomorphs, soil particles, human hair, animal hair, on spray painted surfaces is used to solve forensic cases. The final characteristic is that the approach should use new technologies that will improve the effectiveness of this approach. The article proposes a new approach that embraces knowledge of spray painting surfaces and applies it in the context of forensic science. Thus overall, this method is very

effective in solving cases in which spray painted objects were involved in the course of a crime.

Types of Trace Materials

There are various kinds of trace materials that forensic scientists use to piece together the evidence. The various types of trace materials include plants and fungi, soil, human and animal hair. Often, different trace materials available at the crime scene are used together to help prove a case. For instance, when a woman was murdered in Dundee in late February 2010, soil samples and palynomorphs in a suspect’s shoes were successfully used prove that the suspect had visited the crime scene and had made contact with the murdered woman at approximately the same time that the murder had been committed. This proved that the suspect was guilty of the murder (Patricia, Wiltshere, Hawksworth, & Webb Kevin, 2015). In this case, two trace materials were used to identify the suspect. Thus, it is necessary to understand the most common types of trace materials.

Plants and Fungi

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Spectrum of Possible Pollen Types

Forensic scientists exploit clues from spores and pollen grains as independent sets of trace evidence (Patricia, Wiltshere, Hawksworth, & Webb Kevin, 2015). Through experiments and actual cases, palynomorphs collected from items such as hair, clothing, and footwear, have been used to link objects, persons, and geographical locations. This process is carried out through constructing palynological profiles. This is done by quantifying different pant and fungi taxa in a palynological assemblage (Edwards, Fyfe, Hunt, & Schofield, 2015). Each palynological profile is unique because it contains palynomorphs from living vegetation, long dead plants, plants that were removed, and those dispersed from far locations (Patricia, Wiltshere, Hawksworth, & Webb Kevin, 2015). Most importantly, even within a palynological profile, there is spatial and temporal uniqueness between small areas based on the features within the profile (Patricia, Wiltshere, Hawksworth, & Webb Kevin, 2015). This helps in identifying the fine details concerning the case. Hence, palynomorphs offer useful clues that the forensic scientists can exploit to link objects, people, and specific geographical locations to reconstruct the sequence of a crime and identify suspects. Pollens and spores have unique shapes that attach themselves differently on the surface of thermal spray paint coatings based on the features on the surface of the coating. Also, the adhesive nature of these coatings and the palynomorphs is also affected by the presence of other substances such as water. Thus, if forensic scientists have appropriate tools of testing trace materials on thermal spray coatings, they will be able to have more reliable and accurate investigations.

Soil

Soil is an important trace material because it can link a crime to a suspect and link the suspect to the geographical location of the crime scene, which will incredibly prove the culpability of the suspect (Chauhan, Kumar, & Sharma, 2018). Therefore, there is a need to classify different soil samples to enable accurate identification of suspects and linking of clues when solving crimes. Chauhan, Kumar, & Kumar used attenuated

total reflectance Fourier transform infra-red (ATR-FTIR) spectroscopy along with chemometrics to differentiate different soil samples. The aim of this experimentation was to reveal the unique characteristics of organic and inorganic portions of surface and depth soil samples by applying qualitative analysis and multivariate analysis research tools (Chauhan, Kumar, & Sharma, 2018). This method is useful to forensic scientists because it yields high discriminating power. In the qualitative analysis, the average discriminating power for surface soil samples and deep soil samples was 99.35% and 97.38% respectively (Chauhan, Kumar, & Sharma, 2018). In the multivariate analysis, the average discriminating power for surface and deep soil samples was 100% (Chauhan, Kumar, & Sharma, 2018). Given this success rate, forensic scientists should use this method to differentiate soil samples collected as trace evidence. This article proposes that qualitative and multivariate analysis of soil samples on the surface of a spray painted object can be used to link suspects, victims, and crime scenes.

Human and Animal Hair

In the course of criminal investigations, forensic scientists frequently encounter different types of hair as trace evidence. Therefore, forensic scientists must use the best methods to analyze human and animal hairs when proving physical contact between a victim, suspect, and location of crime scene. This will provide investigators with credible data for potential leads when solving a crime. Deedrick & Koch (2004), define hair as a slender outgrowth from a follicle in mammalian skin. Hair is mainly composed of keratin and has three morphological regions, cortex, medulla, and cuticle. These features are illustrated in the diagram below (Deedrick & Koch, 2004).

HairDiagram

Source: Microscopy of Hair Part 1 ( (Deedrick & Koch, 2004).

Thermal Spray Painting

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that have spray painted evidence that may have picked up part of the evidence. Thus, forensic scientists should study how trace materials are deposited onto spray painted objects. This will offer useful clues when solving cases. Hence, this article proposes that there should be more research and application in actual forensic investigations involving the use of trace evidence analysis on the surface of thermal spray painted objects.

Characteristics of Thermal Spray Coatings

Hardness, Density, and Porosity

Thermal spray coatings are preferred because they have a higher degree of hardness compared to normal paint coatings. These coatings are hard and erosion resistant and thus they are useful in devices that wear out easily. During thermal spray painting, the feedstock material loses some of its hardness and density. For metallic thermal spray coatings, the density and hardness of the coating depend on the material used, thermal spray equipment used, and the specific spray parameters that were executed. Generally, spray equipment that releases the feedstock material at higher velocities produce harder and denser coatings compared to spray painting machines that release the spray paint at lower velocities. Different thermal spray processes yield different particle velocities. In ascending order, particle velocities of spray processes are type and temperature of atomization gas used, high velocity oxygen flame, and detonation. The porosity of the spray painted surface depends on thermal spray material, application parameters, and thermal spray processes. Raymond et al conducted over 180 experiments to show the effect of the surface of microparticles with flat surfaces on the adhesive and frictional nature of the surface of the particle (Raymond, Dunn, & Li, 1999). This research revealed that flat surfaced microparticles attach themselves differently on different materials because these surfaces will interact differently with the flat surfaces of the microparticles (Raymond, Dunn, & Li, 1999). This indicates that there is a relationship between the nature of the trace material surface and the nature of the surface of the thermal spray coating used.

Chung et al researched on the adhesion of Bacillus Thuringiensis spores on a planar surface (Chung, et al., 2010). This study revealed that adhesion forces of these spores are affected by the hydrophobicity of the materials used, because capillary forces are involved in adhesion (Chung, et al., 2010). Bacillus Thuringiensis spores have a diameter of approximately 8µm, length of approximately 1.3µm, and have a rod shape (Chung, et al., 2010). Based on the findings of these two experiments, it can be deduced that different race materials will attach themselves differently on different thermal spray coatings. This is because the features on the surfaces of these trace materials are affected by the nature of the surface onto which they are attached. For instance, because of the diameter, length, and shape of the Bacillus Thuringiensis, it will only attach to surfaces and sores that have apertures that are greater than 8µm in diameter (Chung, et al., 2010). The porosity of surface materials is affected by thermal spray material, thermal spray processes, and application parameters (Bhatia, 1999). Thus, different thermal spray coatings will have different sizes of apertures that will facilitate the attachment of trace materials. This article proposes that there should be research on

the way different trace materials are attached on thermal spray coatings based on the hardness, density, and porosity of the coatings.

Adhesion

Bhatia (1999) that thermal spray paintings are highly adhesive compared to normal paint coatings. It is possible to make thermal spray coatings that have tensile adhesions exceeding 34,000 kPa in line with the standards set by ASTM C633 “Standard Test Method for Adhesion or Cohesive Strength of Flame Sprayed Coatings” (Bhatia, 1999). Typical aluminum, zinc, and zinc-aluminum alloys have tensile adhesions ranging between 5440 and 13,600kPa according to measurements by ASTM D4541 “Standard Test Method for Pull-Off Strength of Coatings using Portable Adhesion Testers” (Bhatia, 1999). The article proposes that adhesion of surface materials will affect the ability of trace materials to be attached to the surface of thermal spray paints. The article also proposes that collecting trace evidence on surfaces of thermal spray paint coatings

CONCLUSION

Trace materials can be used to piece together evidence and prove guilty suspects in a crime. Based on the features on the surfaces of trace materials, these materials attach themselves differently onto the surfaces of surfaces. The nature of the surface also affects the ability of trace evidence to be collected. Hence, if forensic scientists understand the adhesivity of different trace materials on thermal spray paint coatings, they can identify objects and suspects involved in a crime. However, there is scanty research showing how trace materials attach onto different thermal spray painted coatings. Thus, there should be more research that involves this approach.

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How to cite this article:

Bandr Fakia., Trace Evidence Analysis in Forensic Science. Int J Recent Sci Res. 9(10), pp.29381-29385. DOI: http://dx.doi.org/10.24327/ijrsr.2018.0910.2851

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