Forensic Science: Physical Evidence is Tangible

Items such as weapons or articles of clothing (these are only examples) that are direct evidence to the people involved in the crime or the crime itself would be classified as physical evidence. Documentary evidence is written or recorded evidence, such as a phone conversation or a written document. Usually, an expert checks to see if the documentary evidence is authentic. Demonstrative evidence is a representation or demonstration that helps to illustrate a crime, or recreate it. It is used in a trial to help illustrate a crime scene and/or the crime, among other things. Testimonies are the evidence and statements that is given by witnesses in court at a trial. Testimonies could be given by someone who witnessed a crime, someone who witnessed relevant things leading up to it, or by someone who is advocating for the defense.Individual characteristics are specific properties that are unique to a particular instance of a common source.

The dna of a bloodstain or the ridges of a fingerprint would be individual characteristics.While a bloodstain would be a class characteristic, the dna of a bloodstain would be an individual characteristic. Every piece of evidence has class characteristics, but not always individual characteristics. Class characteristics would be properties of evidence that are not particularly unique to the source, while individual characteristics would be very much so. There is a name for characteristics that are in-between, which are called "subclass characteristics". The blood type of a bloodstain would be an example for this.Physical properties describe evidence without referring to any substances. These things can usually be perceived with the five senses. Some examples of physical properties are the color, smell, or size of a piece of evidence.

Chemical properties describe the effects of a substance coming into contact with another substance. They describe chemical reactions. Chemical properties are useful when trying to identify the presence of some substances. Forensic scientists only collect soil at the crime scene from the surface. The soil collected is almost always one or two tablespoons each in different places within a 100-yard radius. The location from which each sample was taken is always labeled. Collecting soil in different places will help to see any differences in the soil and how it varies. Sometimes, soil will be collected from a suspect, whether it is on his/her shoe or at the location of an alibi. If it is on a shoe, however, the whole shoe will probably be taken to the lab. Objects with soil on them must be placed in some kind of container such as a paper bag so that if soil falls off, it will not be lost.

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