Forensic Science
Physical properties: Glass and Soil
The forensic scientist must always consider the properties that are important in identifying the properties and uniqueness of the sample matter (evidence). The properties of a sample matter are classified into 2 categories: physical and chemical properties. These properties can be further analyzed using specialized microscopes such as forensic comparison microscopes.
Physical properties, when viewed under forensic comparison microscopes, show some unique properties of a substance such as the weight, volume, color, boiling point and melting point. Those properties can be tested, sometimes with the use of forensic comparison microscopes, without changing the composition. In comparing the physical properties of glass and soil, a forensic scientist must first be familiar with the different properties that are adherent to these samples. The weight, volume, color, boiling point, and melting point of a glass or soil sample found in the crime scene can be analyzed and compared, using forensic comparison microscopes, with the samples that were taken from a suspect or another location. A positive comparison between two different samples taken in different locations will mean a match or connection between the suspect and the crime scene. These data are simple yet provide a systematic and logical proof which is beyond reasonable doubt.
In glass samples, another physical property can be used as evidence – the density of a glass. This physical property can be solved by first acquiring the mass (done by putting the sample in a weight balance) and then dividing the mass by the displaced water volume (as determined in Archimedes principle). It is helpful to know, based on the original article, that there is another physical property of glass called the refractive index which can be used as additional data for the sample evidence.
The chemical property of a substance, however, shows the reaction of a substance when combined with another. An example of this will be wood. When you burn a wood, it will create a combination of oxygen in the air and form another substance; this change shows the chemical property of wood. In the crime laboratory, they have a procedure to determine if heroin is on the specimen of the suspect. They use a reagent called Marquis reagent that reacts with the specimen. The reagent will change to purple if it is indeed heroin. This will be the determinant of the chemical substance and is also an example of a matter’s chemical property.
The Forensic scientist needs to know the type of material or what kind of specimen they must identify before they observe its physical or chemical properties. Forensic equipments such as forensic comparison microscopes are very useful in comparing and identifying different sample tissues. A forensic laboratory will be incomplete without a forensic comparison microscope. Forensic science depends on simple data such as the physical or chemical properties of a sample evidence in order to gather additional data. These data will be analyzed in order to come up with a logical and scientific proof to indicate or release a suspect.
