Soil can provide useful information about link of persons to crime senes because of
its nature as the surface of the ground. The evidential value of soil stands on large
variation in its characteristics. Soil has extreme complexity not only in components
such as minerals, oxides, organic matter, microorganisms and their materials but
also physical nature such as particle sizes and densities. Considering the granite
rock alone, for instance, there is an almost unlimited number of kind. They are
easily recognized according to difference of color, mineralogy, texture and a lot of
other characteristics. Diversity of soil is the results of many kind of soil forming
process on diverse kind of parent materials, that strongly depends on topography,
climate, course of years, botanical and microbiological functions, conditions of
watering, and even human activities. Moreover, there are millions of fossils, external
matters such as pollen and spores and even artificial materials. Forensic soil
examination has been believed to be very complicated because of complexity of soil,
but such diversity and complexity enable us to discriminate soil samplers with high
discriminating power. The biggest problem in forensic soil examination is shortage
of well-trained staffs and expertise for soil in crime laboratories. Especially
mineralogical identification using polarized microscope requires sophisticated and
experienced skill, and it also forces examiners to work patiently for many hours.
Although considering complexity of soil a variety of methods have been proposed
for many years, recent trend of reports has become simplification of procedures and
methods. However, still standardization of forensic soil examination is difficult
because of diversity of soil samples. Methods sometimes must be changed to
optimize for conditions of soil samples.