Crime Investigations

How Locards exchange principle is applied in solving Crime 

The Locards exchange principle is used in Forensic science to imply that the one who perpetrate a crime will bring something into the scene and also leave having taken something away from the crime scene. The Locards exchange principle was introduced by Edmond Locards, whose concept of use has been applied in several scenarios and has produced the necessary results. The Locards exchange principle is what determines what the connection between the perpetrator and the victim had. The Locards exchange principle is applicable in forensic tests and forms the foundation of every other physical test that is performed in a criminal investigative scene. It Provides evidence of the exchange of matter whenever two objects come into contact. The principle investigates the probabilities of pieces of physical evidence that fall into more than one classification of evidence. These are determined by the level at which two people were in contact or a person and other objects relative to the scene. This part of the investigative process is used to prove the presence of other objects and personalities that may not be within the crime scene. The other way by which the Locards principle works is through an analysis of the evidence and their classifications to take out the possibilities from the impossibilities. These classifications of evidence are also used as a determinant of what propels the investigation or what hinders it. The Locards exchange principle functions to evaluate the necessary exchange of matter valuable for cause. 

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How Presumptive and confirmatory Tests are applied in Solving Crimes

Presumptive testing is used to identify or confirm the presence of substances within a sample especially one collected in a crime scene. The determinations always result after there occurs a chemical reaction during the test. The confirmatory tests on the other hand are used to easily identify the presence of a specific biological material. These tests are known to have their differences and are therefore used separately for their different purposes as well. The presumptive test is what the forensic investigators use to narrow down the possibilities of certain substances being present and they help in decision making on what needs to be done next. Presumptive testing follows the Kastle Meyer test in the case of blood as well as the Albrecht reaction and alternates between light sources. The purpose of these is to create an idea of what needs to be evaluated from what does not require evaluation. The confirmatory test in this case follows the Taka Yama test which is no longer listed in the state crime lab protocols. This tests Human blood in what is considered the RSID tests and can have a cross reaction with certain animal blood. The test focuses on the consistency of the presence of human blood in certain objects and offers a detailed report on the relevant results.

For both tests, individualisation is applied and blood tests are done to determine the source. The most common tests are DNA tests which often fall first under this category. This also involves saliva and semen tests as well. The crime is solved through drug chemistry which involves a drug analysis as well as toxicology. The tests are done to assess the probability of controlled substances as well as analyse urine, hair samples and blood to make a determinant of whether a substance has been consumed or not. Presumptive tests are therefore used to establish possibilities, which are then used as a way to reach the conclusive reports and offer conclusive results and findings. Confirmatory tests come into play where the identification of more specific material is done relative to the findings from the presumptive tests. The crime solutions are not dependent on lab reports or affidavits which may not fully reveal the type of tests that were done. The tests are used by defenders to acquire the underlying notes and reports from the analysts. 

Meaning of the term “Miscarriage of Justice and the Factors that may occasion Miscarriages of Justice Miscarriage of Justice refers to the failure of a court or Judicial system to reach the ends of justice especially in cases where an innocent person is convicted. Miscarriages of Justice are the most significant legal issues that have been a catalyst for psychological research over a long period of time. The first factor that may lead to miscarriage of justice is defective science. This involves fraudulent activity that may be perpetrated between the law maker and the person responsible for the crime. The fraudulent activities often result from the need to safeguard one’s reputation or also based on greed and a lack of integrity. The other factor is based on police misconduct and an inability to maintain lawful and orderly character. Police misconduct is also based on a lack of integrity and the need to act based on vengeful and hateful basis. It is also a case common in the search for extra monetary favour as well.

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