You are an instructor for a state crime lab. It is your responsibility to start the basic training for the new candidates that upon completion of their training will report to crime scene units in their first assignments as crime scene investigators.
Your first lesson involves explaining the 2 categories of physical evidence used for identification purposes or comparison purposes.
Your second lesson is explaining the differences between class characteristics of physical evidence and individual characteristics of physical evidence.
Your third and final lesson is to explain the importance of class characteristics and why their analysis can narrow the scope of the investigation for crime scene investigators.
In a 4–6-page paper, prepare your 3-part lesson plan on the instruction you would provide to new crime scene investigator candidates for the aforementioned lessons.
Physical evidence is any material, either in large or small quantities that can determine that a crime is committed through forensic tests and analysis. The physical evidence gives direction to an investigation for a case. It also connects a crime or suspects to another and links up the statement of a victim to the mentioned crime. there are many types of physical evidence which include hair, fingerprints, explosives, drugs, blood or firearms.
Different types of physical evidence are tested through various respective methods. The body fluids are tested through conventional serology or DNA analysis. In conventional serology species are identified and grouped in ABO. The method is not sufficient enough to positively identify a person (Saferstein, 2015). The DNA analysis can identify a person and link him with the crime. If the evidence involves body tissues, samples are collected from the contents of the stomach and the urine through an autopsy.
For the physical evidence containing hairs, a hair analysis is done to determine the person’s race, the body area and the method it was removed. It could be through forceful removal, burn or cut. DNA analysis and toxicology examination is also done. Soils, minerals, and woods are also tested to determine if there could be a possible comparison between two or more soils and matching two different woods found in different locations of a crime scene.
Identification of evidence involves selecting a suitable test to give a characteristic result for an item or a person. It is done by forensic scientists who use various methods of testing such as the DNA sample testing and fingerprint method. They are required to analyze the results which give no reasonable doubts in a court of law. Comparison uses a solid reference and an anonymous which require to be linked. When giving results, there is a probability of the frequency in which events occurred.
Physical evidence has weight or significance. It is fully handled by the jury of laypersons. The physical evidence requires a scientific evaluation depending on an aura of special dependence and trustworthy. Physical evidence is supposed to be properly safeguarded to avoid unfair ruling of a case against the victim or rather the accused. Physical evidence can also be used to exempt or convict a guilty person during trial in a court of law.
Physical evidence is classified into two categories which are individual characteristics and class characteristics. Individual characteristics are properties of evidence that can be traced down to a common origin which has an extremely high potential of certainty. Class characteristics are properties of evidence that does not originate from a single source but a group. The most dependable method of sampling in this category is the fingerprint analysis.
There are differences between class characteristics and individual characteristics of physical evidence. Class characteristics are not put a certain bit of evidence into a group of objects and don’t belong to a particular object while individual characteristics stream down the piece of evidence to a specific of a single source. For example, a white denim fabric could belong to very many pairs of jeans making it a class characteristic. A DNA sample test is an example of an individual characteristic since it can be traced down to one person.
Evidence that matches the individual characteristics is referred to as individual evidence and the one that matches class characteristics is called class evidence. Class evidence takes more time for collection and analysis while the individual evidence takes less time to examine and analyze a single item. Cases that are based on class evidence require a lot of effort in finding proof while cases that are based on individual evidence are easy to analyze and find proof.
There are several advantages of class physical evidence. For example, there is a high chance that multiple class evidence originates from the same source (Roberson & Birzer, 2016). With class evidence, a person may be able to exempt himself from crime and gets away with it. Class evidence provides an addition to the existing evidence-based on objective scientific data. Class physical evidence has more weight compared to any other in a court trial.
There are limitations associated with class physical evidence. For example, class physical evidence value depends on its ability to give support of details and events with adequate data that is free from any errors or biases. Getting physical evidence from class physical evidence to individual physical evidence can be difficult. Questions like the number of handwriting characteristics tie the suspect to a signature and other complex questions are involved.
Class characteristics rely on individual experiences called upon to elaborate on an experience. Some of the evidence is subjective meaning that informants and eyewitnesses are called upon to testify or confess to a crime that happened (Sutton, Trueman, & Moran, 2016). Defining the significance of class evidence in most situations requires one to use the exact mathematical terms which are close to impossible. Approximation is used in most cases when assigning the appropriate probability to most class physical evidence.
Determining class characteristics entirely depends on relation to items such as tool impressions, tire prints, glove prints, and shoe prints. During the first level of examination, these items are sorted out based on the size, make, type and pattern. For example, when a shoe print is located in a crime scene, the first thing to do is get the shoe size and the side of the leg if right or left. If there are three stripes it means the shoe was Adidas, sport type. These shoe classifications will help the investigator to narrow down his focus to the suspect relating to the class classification evidence provided.
The classification may not be positive but it will help the investigator to eliminate all those people who wear a different shoe size. Some shoes may be too feminine, which would also help the investigator to eliminate the males. If any person around the scene of the crime is found to be having that shoe size, he or she automatically becomes the suspect. The level two characteristic involves unique features that develop on the shoe resulting from wear and tear. If the Adidas shoe was worn out, there should be that mark on the shoe print. The investigator looks around for the same print that leads him to the suspect.
Generally, the physical evidence gives direction to an investigation for a case by aiding the investigator to get to the suspect. There are two categories of physical evidence which are class physical evidence and individual physical evidence. The two categories use different methods of suspect identification depending on the weight of the crime. class characteristics are the most difficult to deal with because a procedure of narrowing down to the suspect is applied.
Sutton, R., Trueman, K., & Moran, C. (Eds.). (2016). Crime scene management: scene-specific methods. John Wiley & Sons.
Saferstein, R. (2015). Criminalistics: An introduction to forensic science. Pearson Higher Ed.
Roberson, C., & Birzer, M. (2016). Introduction to Criminal Investigation.