Forensic Science: Materials Identification - Assignment Example

Introduction Criminals have evolved and developed their ways and means of committing crimes. As a result, it has been essential that police departments are a step ahead of these criminals. This has resulted in the development of the techniques used by criminal investigation departments in their investigations so as to provide evidence that can be used to connect a criminal to a crime. It is essential that evidence is provided in a court of law during a criminal case without which a criminal cannot be judged to have committed a crime. Over the years, science and scientific techniques have been used to provide this evidence. However, these scientific techniques have faced various hurdles, opposition and criticism to prove their credibility. As a result, criminal investigation departments have various units in them that undertake scientific techniques to find credible evidence that can be used to incriminate a criminal to a crime. These scientific techniques are part of what has now come to be known as forensic science. Under forensic science are many types of scientific techniques that are used to characterize and evaluate evidence. The evidences available for analysis are numerous, including trace evidence, biological evidence, just to name but a few. In this paper, a particular type of trace evidence shall be looked at. This particular type is known as soil evidence. Its characterization, elemental and mineral analyses of the composition shall be looked at. Later on, the question, ‘Is the forensic analysis of soil discriminating?’ shall be answered. Soil evidence can and has been utilised in many ways in courts of law. This is both in civil and criminal cases. However, in spite of its value as evidence, it has not been utilized to its full capability due to a lack of specialized forensic personnel trained in soil analysis and also because it takes a lot of time to analyse soils using classical techniques (Ritz, Dawson & Miller, eds., 2008). The term used in forensic science to describe forensic analysis of soil is called pedology. Pedology can be defined as a science used in assessing the soil types and the way they are distributed. It seeks to answer important issues such as description, sampling, formation and analysis of soils from micro to megascopic ranges. Soil is classified into two; natural soils and human made soils. This classification aids in the structuring of knowledge on soils. As for natural soils, there are two types of international classification of natural soils globally. They include soil taxonomy and World Reference Base (Siegel & Sauko, 2012). As for human made soils, they are soils which are normally under the huge manipulation from human beings. Under soil taxonomy classification, these soils are classified into human altered soils and human transported soils. The characterization of human made soils is done by spatial heterogeneity. Spatial heterogeneity is from a variety of inputs from artificial substances. The characterization of human made soils is done through difficulty, heterogeneity and diversity. This characterization has allowed forensic soil investigators to differentiate between soils that look to be alike (Siegel & Sauko, 2012). In the forensic investigation of soil, soils that can be used as evidence to connect a suspect to a crime are collected. After collection, the soil is characterized. Before characterization, the soils are categorized as follows: the soil samples that are in question. These soil samples are normally of unknown source or they are in dispute, usually from the victim or the suspect. There are also the control samples which are from a known source. The source is normally connected to the crime scene. The last category is the alibi samples that are from a known source. They avail a level of distinctiveness of both the control and questioned samples. The alibi samples are important because they avail a thorough examination of the soil samples that are been compared. This enhances accuracy and validity of the soil evidence in a court of law (Siegel & Sauko, 2012). Soil Characterization The characterization of soil evidence is simple. It makes use of various techniques. Soil characterization is divided into three stages that include initial characterization of all soil samples, Semi detailed characterization of the chosen soil samples and detailed characterization (Siegel & Sauko, 2012). Initial characterization Initial characterization of all soil samples collected as evidence is done for the purposes of screening and choosing the important samples. The characteristics that are analysed at this stage include soil colour, texture, consistency and structure. Structure is analysed through stereo binocular microscope (Kobilinsky, 2011), Soil colour is a vital for soil identification. According to Kobilinsky (2011), the analysing of soil colour for forensic investigation is done by initially drying the soil sample at around 100oC. It is then observed under natural light. This evaluation is usually done for soil samples with particles of nearly the same size. A colour chart is then used to evaluate the Munsell colour numbers for exact colour depiction. The colour can also be evaluated by use of a Minolta CM – 2002 photospectrometer (Kobilinsky, 2011). The device has a visible wavelength of between 400 to 700 nanometers. Distribution of soil particle sizes is also determined. It is done by moving the soil samples through several sieves where the size of sieve pores reduces from the top to bottom. It can also be done by evaluating the speed soil grains take to settle in a fluid. Also, devices that assess the soil particle sizes are used. These devices include microscopes (Kobilinsky, 2011). The Stereo binocular microscope is a vital device for forensic soil analysis. It is used for the examination of the soil particles obtained. In assessing soil samples using stereo binocular microscopes, the features of the particles are observed. These features include their outline, shape, weathering and polish. Also, the various types of grains are counted. This information is then recorded in numbers. The soil samples are then chosen according to their relation with the crime scene (Kobilinsky, 2011). Semi detailed characterization Semi detailed characterization is done on the chosen soil samples. It involves the examination of the mineral and organic composition of the selected soil samples. One method used for this characterization is x – ray diffraction. X – Ray diffraction involves passing x – rays through a soil sample particle from the selected soil sample (Ruffell & Wiltshire, 2004). The angle of the diffracted x – rays is then measured. In fact, the pattern of diffraction can be recorded on a film using an electronic detector. Data obtained from x – ray diffraction can be interpreted by measuring the d values and strength of the x –rays. These results are then compared with scientific outline on minerals. It can also be interpreted by direct comparison of the pattern of produced x – rays with that of a known mineral. The elemental analysis using x – ray diffraction is done through identification of the crystal structure (Kobilinsky, 2011). Infrared microprobe analysis is used at this stage for evaluation of minerals. This technique avails distinct information on the chemistry of intricate minerals that are found in the selected soil samples. It is known that many soil samples have around 3 and 5 mineral varieties (Ritz, Dawson & Miller, eds., 2008). In infrared microprobe analysis, the mineral part of the soil is divided from the organic part by use of a washing or flotation procedure. This is done before getting the profile of the minerals in the selected soil samples. The mineral part is the one that is important for infrared microprobe analysis. During the evaluation of the minerals in the soil samples, infrared microprobe analysis utilizes oil that is made up of an uncomplicated hydrocarbon which is composed of an easy infrared spectrum. This is in stark contrast to the organic constituents of the soil samples which have very intricate spectra. The spectrum produced is compared with a library of ATR IR spectra (Ritz, Dawson & Miller, eds., 2008). Infrared microprobe analysis is utilised to recognize the minerals in the selected soil samples. It is also used in comparison of the suspected samples with the known samples obtained from the scene of crime (Ritz, Dawson & Miller, eds., 2008). Diffuse reflectance infrared Fourier transform spectroscopy is also used. It is a method that does not destroy the selected soil particles. It takes a short time to perform. It should be noted that the mid – infrared part of the electromagnetic spectrum is receptive to clay minerals, organic substances and sand as infrared light is absorbed at the vibrational frequencies of molecular functional groups that make up the substances. Mineral and organic substances quantification is also done using magnetic susceptibility methods. These methods are utilised to detect minerals that have magnetic properties in the selected soil samples such as magnetite. The usage of these methods is important to detect minerals that are in the selected soils samples at quantities below the levels of detection by other methods such as x – ray diffraction and diffuse reflectance infrared Fourier transform (Siegel & Sauko, 2012). Detailed characterization Detailed characterization of minerals and organic substances in specific soil particles is done using various analytical methods after the soil sample has been selected and semi - detailed characterization done (Kobilinsky, 2011). One method used to evaluate the chemical constituent of particles is using the scanning electron microscope. This instrument has a vast range of magnifications that start from 25× to above 650,000×. Hence it magnifies particles to so many times their original magnitude. Kobilinsky (2011) notes that when utilising it, it’s important to note that two particles can ever be precisely similar. However, this does not mean that the two particles are different. The scanning electron microscope is capable of evaluating the elemental constituent of the soil particles being evaluated. This is made likely as there is production of x – rays once the beam of electrons hits the particles. The SEM is coupled with an x – ray analyzer where the x – rays that are produced are classified through the values of the wavelength or energy that are connected to distinct elements. The x – ray analyzer then generates information which recognizes the distinct elements that are in the particles of the soil sample been analyzed. Quantity of each element is proportional to the strength of the generated x – rays (Kobilinsky, 2011). Fourier transform infrared spectroscopy is another method used in detailed characterization. It is a chemical method used to characterize the organic composition of the soil sample. It is non destructive. This method is also utilised to identify the minerals present and their organic origin (Kobilinsky, 2011). The procedure of Fourier transform infrared spectroscopy involves the production of light through the spectrum needed. The soil sample particles then absorb light in relation to their chemical features. A detector then gathers the generated radiation after it has gone through the soil sample particles. After which, a software is used to evaluate the data collected. Using known spectra of organic and inorganic substances, the results are compared for identification. Fourier transform infrared spectroscopy avails a general chemical signature of the mineral and organic constituents of the soil sample (Dawson, et al., n.d). Soil characterization along with the methods of analysis of soil enables the answering of the question, ‘Is the forensic analysis of soil discriminating?’ The answer is yes. This is because of the use of analytical tools such as scanning electron microscopes which magnify soil particles to thousands of times their original sizes. Also, through identification of minerals, then soil discrimination is achieved in forensic soil analysis as minerals are vital constituents of numerous soil types. Also, the utilization of organic constituents in forensic soil analysis enhances discrimination in soil samples that may be otherwise alike (Cox, et al., 2000). In conclusion, it can be concluded that forensic analysis is discriminating and highly valuable in linking a suspect to a crime with credible evidence. References Cox, R. J., Peterson, H. L., Young, J., Cusik, C. & Espinoza, E. O., 2000. The forensic analysis of soil organic by FTIR. Forensic Science International, [e – journal] 108(2), pp. 107 – 116. Available through: Sciencedirect website http://www.sciencedirect.com/science/article/pii/S0379073899002030 [Accessed 18 April 2014]. Dawson, L., Hillier, S., Macdonald, L., Mayes, B., Ross, J. & Robertson, J., n.d. Chemical Profiling of Soil for Forensic Application [pdf] The Macaulay Land Use Research Institute. Available at: http://www.hutton.ac.uk/webfm_send/608 [Accessed 18 April 2014]. Kobilinsky, L., ed., 2011. Forensic Chemistry Handbook. John Wiley & Sons. Ritz, K., Dawson, L. & Miller, D., eds., 2008. Criminal and Environmental Soil Forensics. Springer. Ruffel, A. & Wiltshire, P., 2004. Conjuctive use of quantitative and qualitative X – ray diffraction analysis of soils and rocks for forensic analysis. Forensic Science International, [E – journal] 145(1), pp. 13 – 23. Available through: Sciencedirect website http://www.sciencedirect.com/science/article/pii/S0379073804001690 [Accessed 18 April 2014]. Siegel, J. A. & Saukko, P. J., 2012. Encyclopedia of Forensic Sciences, 2nd edn. Academic Press. Read More