Organic and Inorganic Matter
When selecting an analytical technique you the Forensic Scientist must look at all aspects of the item that tare to be analyzed. Such questions to ask your self are is this organic or inorganic? Is the item qualitative or quantative? Is the item a solid or liquid?
When selecting analytical techniques one must first resolve the question is the object or substance organic or inorganic?
An organic object is a substance that contains carbon and often small amounts of hydrogen, oxygen, nitrogen, chlorine, phosphorus, plus other elements. Inorganic is a chemical compound that is not based on carbon.
Next is to determine whether the object or substance is qualitative or quantative this determination of facts that lead to a sample product of identification of the substance that you as a Forensic Scientist are looking for. Qualitative objects are made up of one single element. Quantative objects or substances are made up of many different molecules and elements combined. When dealing with quantative items the Forensic Scientist must use a technique that will single out the breakdown of the elements and molecules in order to extract exact items to be examined by the Forensic Scientist.
There are many techniques that can be used to analyze materials, substances, and liquids some of which include Chromatography, Spectrophotometer, X-ray and microscopy.
Chromatography is used for substances that contain multicomponent specimens that need to be purified.
Gas Chromatography or GC identifies illicit substances by using stationary liquid to produce gas that rises into the surrounding environment. The sample is injected into a heated chamber, a constant stream of nitrogen gas flows through the injector forcing the sample through a series of seven columns that has a thin film of liquid present. The columns separate the gases and then the gases enter the detector that activates the recorder producing a recording that traces peaks and valleys based on a timed scale that identifies the concentration of drugs.
Thin Layer Chromatography (TLC)
A gel coated plate is spotted with a droplet of a substance sample from a suspect. Then the plate is placed into a closed chamber that is filled with a rising solvent. The greater the affinity of the substance the greater the speed it will travel up the plat. Then the plate is analyzed and compared with other plates that have been tested with substances similar to the one that has been tested.
Electrophoresis separates substances by their migration rates on a stationary solid phase. This process involves a gel coated plate when under the influence of electric the substance is migrated across the plat due to variances in the size the sample moves across the plat at different variables of speed these speeds can be compared with a chart of other substances until the one that is tested becomes known.
Spectrophotometer
This process uses variants of light to measure the absorption rate of light energy by a substance. The Visible light is light ranging from red to violet. Wavelengths are the distance between crests and adjacent waves. Frequency represents the number of waves that pass through a measured point per second. The first part of the spectrophotometer is the Radiation Source then you have the Monochromator it is a device made for isolating individual wavelengths or frequencies of light; it consists of a prison and a slit. The next piece of the device is a sample holder, this holds the substance that is being analyzed by the light source. The detector is the second to last part it converts electromagnetic radiation into signal. Last the Recorder produces a record of the signal.
X-ray is used for crystalline materials such as solids with organized atoms. A Forensic Investigator may watch the way X-ray diffraction interacts with a substance and record the results. The process of X-ray diffraction involves analyzing the way X-rays refract off of the crystalline substances. During the process of using the X-ray it will pass through crystals leaving dark bands called diffraction patterns these diffraction patterns allow the analysis to fingerprint compounds.
The Microscope helps with analysis of many items. Identifying evidence and trace evidence with a microscope is important to making a good case against a suspect. Microscopes have a large range of visible and virtual imaging that identify, compare, and analyze objects, elements, substances, liquids and fluids. The five main microscopes are the Compound Microscope, Comparison Microscope, Stereoscopic Microscope, Polarizing Microscope, and the Micro spectrophotometer.
The Compound Microscope consists of ten parts base, arm, stage, body tube, coarse adjustment, illuminator condenser, objective lens, and eyepiece. The compound microscope illuminates the subject matter by allowing light to pass through optical lenses to form an image on the retina of the individual’s eye. The magnification of the subject is the total magnifying power of the objective and the eyepiece lenses.
The Comparison Microscope allows for a side by side display that provides the user the ability to analyze both subjects making a comparison of the similarities and differences of the subject being magnified. It uses the bridge that has mirrors and lenses that join two independent object lenses together for analysis of two specimens through the same eyepiece.
The Stereoscopic Microscope is the most frequently used microscope with magnifying power of up to 125x having the capability to show a specimen in third dimension also being able to view a subject at many different angles and a variety of image manipulators that allow the technician to look at the Stereoscopic Microscope from many views.
A Stereoscopic Microscope can have a polarized lens installed as an accessory along with an analyzer to make the Stereoscopic Microscope into a Polarized Microscope. The Polarized Microscope allows the technician to view the subject with a wide verity of colors that distinguish the subject and makes the subject easier to identify. The basic use of a Polarized Microscope is to observe minerals found in soil.
The Micro Spectrophotometer is a machine that links a spectrophotometer to a microscope it has a high magnification that is capable of fining very tiny minute pieces of evidence.
The Scanning Electron Microscope (SEM) emits an electron ray that is produced by burning tungsten. The Scanning Electron Microscope is one of the highest magnifications magnifying an object up to one hundred thousand times, it scans three hundred times better than any optical microscope. The Scanning Electron Microscope can further analyze objects by using an X-ray coupled with the SEM Microscope.
When choosing a technique for analyzing elements, liquids, and substances you must weigh all of your options and find the one that suits your needs as the Forensic Investigator. Using the correct process can make a large difference in what your outcome is. Make a plan, document the steps you took to come to your conclusion, photograph your evidence, and document your conclusion to prepare for trial.
References
Explore Forensics (2010) from source http://www.exploreforensics.co.uk/understanding-trace-evidence.html
Fisher, Berry A. (2004) CRC Press, Techniques of Crime Scene Investigation
Saferstein Richard (2007) Pearson Prentice Hall, Criminalistics, An Introduction To Forensic Science Tenth Edition
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