What You Need to Know About Soil Sample Microscopy For Forensic Examination
Generally, forensic examination deals not only with soil but other materials such as glass, explosives, etc. Actually, there is a course which is called comparative microscopy of soils wherein students are taught about soil comparisons. Soil samples are taken and separated into slat, sand, dust, pollen and other minerals. These samples are interpreted within the context of forensic and geological principles and are examined through light microscopes.
Soil is not only useful for classroom setup but more for solving criminal cases. It gives useful information regarding the association of persons in certain crime scenes. This is due to its characteristics being the surface of the ground. Soil can take diverse forms because of its numerous formation processes. Since forensic examination of soil can be so complex, experts and well trained staff are needed to work patiently for long hours. Aside from expert hands, microscopy processes and high end microscopes are needed to handle these fragile forensic soil examinations.
Minerals for soil samples have identifiable properties and diverse densities. The minerals to be used as samples for forensic examination can be categorized into heavy and light. Heavy and light minerals are bounded separately approximately at 2.9 grams per cubic centimeters. Minerals, specifically those small-sized, are commonly identified with the use of spectrographic techniques and x-ray diffraction.
The quantity of soil sample needed for analysis will depend on which type of forensic examination will be conducted. Generally, 1 cup of soil sample is needed in any analyses. Samples with many coarse elements and gravel maybe insufficient thus more amount of soil will be required by investigators. Examiners will be lucky if unique particles like distinctively colored fibers, paint chips or glass fragments are in the soil sample. Microscopy and examination can be limited to the unusual components of the soil. This examination can thus be an initial step on a successful forensic examination.
Low power stereomicroscopic and macroscopic observations are important as initial steps in soil forensic examination. Stereo binocular microscopes on the other hand help determine numerous minerals or mineral sites present in soil sample. The low power, wide field stereo binocular microscope provides an erect 3 dimensional figure which makes it perfect for controlling a sample of soil. Polarized or petrographic microscopes are used in mineralogical identification and to positive determination of the sample. These microscopes are different from stereo binocular because these have filters that can polarize light and rotate the attachments and state that are used to view the effects of the lights that passed through certain minerals.
The other microscopes that are of value to forensic soil sample examination are the electron and scanning electron microscopes. Using these instruments, the forensic geologists can extremely examine the small particles in the minerals with a magnification of approximately 100, 000 times. Elemental analysis and determination of pH size particles can also be utilized in combination with texture, mineral composition and color.
There is also a process known as diatom microscopy where diatoms are usually observed. Diatoms are very delicate unicellular organisms that can easily propagate in many kinds of environment and even during wet conditions. Due to the assemblage and distinctive differences on diatom species, they can play a vital role in forensic examination.
Another microscopic soil analysis being done is with dust particles. Dust can be comprised of numerous types of fibers and particles; thus it can be a rich sample for criminal investigation. There are 5 dust sampling method that is fitted for microscopic analysis.
First is the adhesive tape sampling where a clear cellophane tape is attached into the slide of a glass microscope. Second is the brush sampling where synthetic bristle brush are used to gather samples of lightly or loosely attached particles. A resealable plastic bags or glassine envelopes are used to preserve these samples. The third method is the scrape sampling where scalpels or razor blades are used for stains or particles which are tightly contained on surfaces.
The fourth method is the wipe sampling where wiping materials such as filter papers, cloths and swabs are used to gather samples from contaminated surfaces. A resealable plastic bag is also used to preserve the samples. The last method is the vacuum method where a medium and smaller sized hand-held vacuum is utilized to collect samples. Vacuum sampling can only collect limited particles and some may not be subject to microscopic examination.
Soil proves to be an important tool as physical evidence in civil and criminal proceedings. Forensic examination on soil samples should be very exact and must be done by skilled geologists or scientists and with the aid of different microscopes. If done carefully, soil sample forensic examination through high-tech microscopes can be very beneficial in any law enforcement agencies to solve many crimes.
