Chain of Custody: Evidence

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Table of Contents

Introduction
Locard’s Principle of Exchange
Individual Identification
Putrefaction in Animals
Personal Reflection
Works Cited

Introduction

Evidence from a crime scene needs to be presented before the court of law, without any alterations, and questioned to determine various facts of a given case. However, there have been instances where the evidence of a given case has been manipulated for various reasons before being presented in the courtroom. Thus, following the concept of chain of custody, it is essential for investigators to chronologically document the evidence that is present to determine how it was collected, the people who were in charge of its custody, its analysis, and the means through which it has been transferred to the court. With such a system in place, it will be difficult for anyone to manipulate or misrepresent any evidence in a criminal case. Therefore, the prosecution can confidently use this information to accuse or acquit an individual. Consequently, it will be difficult for an accused individual to deny that he/she had the substances that have been presented before the court of law as evidence after proper documentation and storage in police custody before being presented in court.

Locard’s Principle of Exchange

The application of forensic science in criminal investigations was introduced by different people who came up with techniques and procedures that made it possible to use physical evidence to solve a crime (Petersen 4). After the success of this concept, another group of individuals saw that it was necessary to arrange these principles and techniques into a single discipline; forensic science. Dr. Edmond Locard was one of the pioneers in forensic science. Through his work, he managed to contribute to forensic science by coming up with several principles and techniques. The principle of exchange is a prime example. According to this principle, a perpetrator will introduce a new element into the crime scene and at the same time, he/she will leave with some elements that were originally part of the crime scene (Petersen 5). In this regard, Locard believed that an individual could be linked to the crime scene by the dust particles and items of evidence that he/she might have carried from the scene of the crime. Therefore, this concept ties individuals with the physical evidence that they might possess, the victims of the crime, or specific actions that are associated with the crime (Petersen 5).

Individual Identification

Forensic identification can be used to identify individuals and place them at a crime scene. Investigators and forensic scientists use various techniques to identify individuals at a crime scene. Frictional ridge analysis especially with the use of fingerprints has been used to positively identify individuals and place them in a crime scene. This technique was developed during the 19th century when government agencies adopted the use of fingerprints as a means of personal identification. Sir William Herschel, a British administrator in India, made it mandatory for his employees to sign official documents using their signatures and their fingerprints (National Research Council 145). However, it was not until1891 that fingerprints were used to fight crime. A year later, Juan Vucetich solved a homicide using the fingerprint technique. In this case, a woman had killed her two children and later killed herself in an attempt to shift the blame to someone else (National Research Council 145). Since then, the use of fingerprints has been common in criminal investigations.

Another technique that forensic scientists use to identify people is DNA analysis. Just like fingerprints, every individual has unique DNA. Thus, investigators use biological samples such as hair, semen, and blood to conduct DNA tests (mitochondrial DNA tests or STR DNA tests) to identify the remains of an individual, to place an individual in a crime scene, or to determine ownership of property such as toothbrushes and clothes (National Research Council 133). Sir Alec Jeffreys was the pioneer of DNA fingerprinting in 1984 (LLC 5). Three years later, this concept was commercialized and it has been used to solve many crimes since then. Impression evidence is also used to identify and place individuals at a crime scene. The main sources of impression evidence in criminal cases are shoe marks and tire tracks. Through their investigative works, William Bass and Juan Vucetich played a critical role in applying this technique to solve crimes.

From my analysis, I believe that the use of fingerprints is the most effective method of presenting evidence in a courtroom setting. Usually, people tend to leave their fingerprints at a crime scene. Given the available database of fingerprints in government agencies and other organizations, it will be easy to identify the person who committed a given crime and place him/her at the crime scene. However, for this technique to be sustainable, it needs to be supported by other techniques and sources of evidence.

Putrefaction in Animals

The organic tissues contained in an animal comprise chemical energy that breaks down into simpler products as a result of a lack of maintenance from biochemical processes within the body. Anaerobic bacteria that were present in the body of the animal when it was alive catalyze this process, hence leading to decomposition (Janaway 22). Two to three days after death, discoloration occurs on the skin. This will be accompanied by subsequent swelling of the abdomen as a result of the accumulation of gases within the intestine. Several days later, the veins will become visible due to increased discoloration. At the same time, the abdomen will continue to expand hence leading to the formation of blisters. After 14 days, the skin will bloat, and due to the softness of the tissues, the organs will start to burst and the nails will fall off. Eventually, the face will not be recognizable due to the liquefaction of the soft tissues.

On the other hand, however, insects might have access to the body. For instance, maggots will invade the body and start hatching especially under the skin. As a result of the feeding and respiratory activities, the skin, fingernails, and hair will start to fall off from the body of the animal. This in turn will lead to an increased release of the gases that are contained in the body into the surrounding environment. The gas that has been emitted from the body usually affects the surrounding vegetation. These gases include hydrogen sulfide, carbon dioxide, and methane (Janaway 24). These gases usually have varied effects depending on the plant species that are present. However, in normal circumstances, the presence of carbon dioxide enhances respiration in plants, hence leading to increased growth (Janaway 24).

Personal Reflection

From the information that has been covered in this course, I am amazed by the effect that forensics has in solving crime. Astonishingly, fingerprints have been used to solve crime since the 19th century. With the presence of such knowledge and techniques, I believe that I can be one of the best forensic investigators in the world who will use the evidence that is present at the crime scene to put the people responsible for the crime in prison following the law.

Works Cited

Janaway, Richard. Microbiology and Aging. Boston: Springer Science, 2009. Print

LLC. N.d. History of Fingerprinting. N.d. Web. 2012.

National Research Council. Strengthening Forensic Science in the United States: A Path Forward. New York: Sage, 2009. Print

Petersen, Willian. n.d. Locard’s Principle of Exchange. n.d. Web. 2013.

World of Forensics. Crime Scene Investigation: Cross Contamination. Chicago: Cengage Learning, 2006. Print.

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Chain of Custody: Evidence

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