The particle size analysis of soils and its use in forensic science--the determination of particle size distributions within the silt and sand fractions.
Methods are described for the determination of the particle size distributions in small soil samples using a Coulter Counter Model ZB for the silt fraction (60μm–2μm) and conventional sieving for the sand fraction (2mm–60μm). An examination of the reproducibility of the methods using duplicate 1·5g samples of eighteen different soils has shown that they are highly reproducible and that the differences between the soils were easily demonstrated both in the silt and sand particle distributions. The methods have also been shown to be reproducible for sample weights as low as 200mg of whole soil.
Forensic Examination of Soil Evidence
Soil can provide important information to criminal investigations as transfer evidence because many criminal cases take place under circumstances such that soil transfers to a criminal or victim. The variation in soils from place to place makes soil valuable evidence to prove linkage between a suspect and a crime scene. Soil is a complex mixture with a variety of mineralogical, chemical, biological, and physical properties. Considering such complexity, a variety of methods have been developed for forensic science purposes. Because minerals are an important component of soils, mineralogical examination is essential in forensic soil identification. Additionally, many other methods can be applied to raise the discriminating power, but not all kind of methods need to be used. What is important is that examiners select an appropriate combination of methods by considering the context of the soil samples. This report summarizes a wide range of reports on the analysis of soil components and of closely related materials such as plant fragments, pollen and spores, and diatoms, with emphasis on the importance of screening tests consisting of several simple techniques. The soil formation process involves parent materials, temperature, water condition, vegetation, time, and the chemical processes of solution, oxidation, reduction, and even human activities. The history of a soil's development as the results of such complex soil formation process is strongly reflected in soil color. The systematic observation of multiple soil colors is especially useful for screening.
The discriminating power of density and refractive index for window glass.
The concept of discriminating power has been applied to the attributes density and refractive index for window glass. The discriminating power has been calculated at different error factors for the two attributes measured separately and then for both attributes combined. The results are discussed in terms of which attributes should be measured routinely for window glass.