Forensic Analysis of Soil - Assignment Example

 Forensic soil analysis refers to the use of soil science and other disciplines such as geology and geochemistry to aid in investigating a criminal act. Since each soil has unique characteristics that serve as identification markers, soil can be traced and matched to each other. For example, sand fixed in the sneaker of a criminal can be forensically be analyzed and traced back to specific sand type found in certain place where murder victim was discovered. On the other hand, soils are situated and transmuted sediments. Sediments are the original solid particles that are weathered and transported to different places. Soils develop on these accumulated sediments because of physical and chemical weathering. The characteristic of uniqueness of the soil such as horizon that has unique physical and chemical properties, color, structure and texture are the common features that and in forensic analysis. Characterization Techniques use in Forensic Analysis of Soil Techniques currently used to characterize soil samples rely on either physical descriptors such as color, density gradient, particle size determination and microscopy or chemical analysis chemical analysis such as elemental composition. However, these characterization techniques are not adequately capable of investigating organic compounds present in the soil. On the other hand, Fourier Transform Infrared Spectroscopy (FTIR) technique involves collecting a range of soil sample that has already undergone oxidative pyrolysis hence all organic have been degraded. This spectrum is spectrum is subtracted from the spectrum of the same sample that contains the organic prior to pyrolysis. The result IR spectrum represents the organic portion of the sample. a) Characterization Technique of Color Samples of soil collected from within the agriculture site where the murder scene is committed to the victim. After soil samples are collected from the surface to 3.4 below, the sample from the scene is compared with various color layers of different places several miles from the ‘agricultural site’ of the scene. Each sample is compared to every color in the Munsell Color Chart and is assigned a Munsell value. A second examiner later confirms each color assignment. The assigned values help to indicate the soil color both before and after pyrolysis is similar within the ‘agricultural site’. Color is a useful tool to distinguish soils that do not share a common color to show that they do not have a common source. Lastly, those soil samples that cannot be distinguished using color are submitted to a more rigorous analysis to eliminate common provenance. b) Characterization Technique of using Organic Content Organic content refers to component of soil that consist plants and animal remains at various percentage. After samples of soil are collected, each sample is weighed on an analytical balance heating it for 15minutes at 650 degrees Celsius in a muffle furnace. After heating, the pyrolized soil sample is the reweighed again. Further heating and reweighing ensures there is no further weight loss. Lastly, the percent of organic content is calculated from the weight loss on heating. The result is given a value that is compared to the range of different organic content of various places that aid the investigation of any criminal act within the suspected area that matches the result on the percent organic content. This is simplified when the percent organic content obtained matches with the statistical value of percent organic content of a particular place(s). consequently, this method has a major shortcoming especially where the result give a wide range of percent organic content that makes this analytical technique a poor choice for concluding common provenance in forensic comparisons. c) Characterization Technique of using FTIR Spectroscopy This kind of soil analysis technique involves pressing each soil sample into a KBr pellet and collecting the spectra on Nicolet 5SXC FTIR using Nicolet Omnic software. It implies the condition that each pellet must be translucent. Every KBr pellet is then reground in a mortar, placed in a glass vial and heated for 15 minutes at 650 degrees Celsius in a muffle furnace to decompose the organic matter. An IR spectrum collected after cooling the soil samples. The spectra obtained after pyrolysis is subtracted from their corresponding samples before pyrolysis. Lastly, the resultant subtracted spectra represent the absorption by the organic component of soil. The result is matched with statistical results in different areas and assists in investigation of a criminal occurrence by the forensic scientists specifically in areas that have a similar match with the results of this kind of analytical technique. Unfortunately, this technique is not always advisable to use because the FTIR spectrum of untreated soil is always dominated by inorganic components that exhibits similar spectra. This makes it difficult for forensic scientists to make wise decisions during investigation process. d) Characterization Technique of using Thermal Analysis Differential Thermal Analysis (DTA) is a technique that records the physical and chemical transition of soil particles and a reference against time as the soil is exposed to identical heating or cooling at a precise controlled rate. This technique is used to confirm the soil organisms in oxidation under the experimental conditions. During differential thermal analysis, event such as melting, glass transition or decomposition is recorded as a peak or large variation in the smooth trace during the heating cycle. Recording temperature range at various stages during the soil heating will assist to determine the characteristics of different soils. Since different soil will give differing results, as a forensic scientist, it aids to give details of a criminal offence that need to be investigated. Unfortunately, carrying out this analytical experiment under certain condition such as under a nitrogen atmosphere do not give results in certain range of heating that would hinder a forensic scientists from making essential observation for certain conclusion important to carry out investigation. On the other hand, this technique can be used to carry out experiments to determine organic content of a soil (Horswell 102-108). e) Characterization Technique of Soil Mineral Composition Different soil has mineral composition different from each other. In this technique, the most different soil mineral investigated include amount of concentration of kaolinite, anatase, albite, microcline, goethite and quartz since they are the common sol minerals found in most soils. The composition of NIR spectrum shows several characteristics of the soil such as absorption. The characteristics of the sample soil being investigated are used to compare the spectra of the soil determine the percent content of kaolinite and quartz according to XRD results. The XRD results of all spectra are presented on a common scale to make it possible to compare peak intensities of each soil sample. Lastly, all spectra collected from the minerals present in different soils acts as evidence of the soil that have significant amount of these minerals hence it is possible to predict the NIR spectra of a soil through estimated mineral concentration. A forensic scientists uses these collected spectra from the soil and compare them to Chemometrics methods and Multivatiate Data Analysis in order to establish whether the method available are capable of distinguishing between related soils and matching their similarity to obtain a conclusion of an investigation. PCA and FC analysis of the raw soils through NIR investigation reveals the different characteristics of soil that warrants deeper investigation on a criminal act at the suspected scene. On the other hand, this method shows discrimination because investigation is only limited to the soli samples that are rich with common minerals excluding investigation of other soils with different minerals that would also contribute positively to the matter being investigated (Lacks 178-183). f) Characterization Technique of Moisture Content in Soil Moisture content of soil is also another characteristic that is use to analyze soil. The moisture content of collected soil samples play an important role in the matching and discrimination of various spectra. Using the wet sampling method to determine the soil moisture in collected samples a forensic scientist can easily analyze the soil samples to investigate to a certain criminal scene. Different soil component possesses different ability in moisture retention. Therefore, taking a sample of soil attached on the victim of the criminal act at the scene of the act and analyzing it can help to investigate the criminal issue through the Principal Component Analysis that distinguishes the component of moisture in different soils. For example, moisture content of sand and clay soil differs in a substantial amount and therefore, the Wet Sampling Method of soil can play a useful role in distinguishing the various spectra of sand and clay soil. When a forensic scientist obtain the moisture content of various sample of the soil being investigated, he or she compare the results with the moisture content of soils found in various part the suspected places where the criminal act have been committed. The soil sample that matches with the results gives direction of investigation. Unfortunately, principal of component analysis is also discriminative because it focuses only on the soil moisture content by distinguishing differences between the backyard soil and the melcann sand spectra by use of dry brushed and wet sampling methods. Therefore, this excluding other characteristics that can give essential information on the issue being investigated (Brownell 571-581). Although there are benefits associated to NIR analysis such as minimal sample preparation, non-destructive and can be completed within a short period while conduction analysis on soil in forensic laboratories all over the world, there is further research that needs to be done to come up with convincing conclusions. Further work is needed to in to the effect of every soil characteristic especially on the NIR spectra to determine moisture content and on the Differential Thermal Analysis (DTA) of various soil and then compare the results using Chemometrics methods in order to prove to be convincing. It is also important to note the soils that makes up the impression is not only soil that can provide adequate important evidence information. It is important to take into consideration the soils in the surrounding areas. This will increase the possibility of coming up into a conclusion with adequate and vital evidence information. List of References Horswell. 2004. Influence of Soil Chemical Structure and Properties and Determinants of Soil Components. Journal of Minerals Engineering. Ireland, P.M.2009. Contact Charge Accumulation and Separation Discharge. London: Journal of Electrostatics. Munsell. 2004. Methodology for Studying Particle-Particle in Granular Materials. Journal of Soil Analysis . Young, J.E. and W.E. Brownell. 2006. Moisture Content among Different Soils. New York: journal of the American Ceramic Society. Read More