Forensic Science

1. Locard’s Principle The Locard`s Exchange Principle states that when two things come in contact with one another they affect one another in a particular way (Houck & Siegel, 2006). This means that everywhere we go we leave evidence and take evidence. This principle is used in forensic science to pursue perpetrators of a crime. This principle is applied to the scenes of the crime in which the perpetrator comes into contact with the scene. The perpetrator will always bring something into the scene and leave with something from the scene as a result of their contact (Schafer, 2008). Trace evidence is any kind of material that is left at or taken from the scene of the crime or the effect of contact between two surfaces which can be the shoes and the floor/soil or fiber from where the perpetrator sat. These trace evidence is collected from the crime scene and victims by a team of specialized police officers. This information provides factual evidence that can be used accuse the perpetrator. 2. Principle of Individuality The Principle of Individuality states that there are no two things that are completely identical (Saferstein, 2007). According to this principle, objects can be indistinguishable but they cannot be identical. This means that there are no two people with exactly the same features or characteristics. Every person has individual characteristics that differ from those of others. It also applies to other objects which are said to be different from one another. It all depends on the ability to distinguish between two objects using the information and the measuring tools available. This principle is used in forensic science to examine trace evidence that has been collected from the crime scenes (Gaensslen et al, 2008). The evidence is analyzed for finer details that are unique from other objects. This information is used to link the evidence to a particular perpetrator of the crime and prove beyond any reasonable doubt that he or she was the one involved. 3. The Forensic Scientist Forensic scientists have a great responsibility of investigating the crime which determines liberty of human beings. They should present accurate results and defend the techniques used to conduct the analysis. It is therefore important for these scientists to uphold high ethical standards. Impartiality is the most important ethical consideration for forensic scientists (Schafer, 2008). They must avoid being influenced by any party in the case to alter the results. The evidence should be thoroughly analyzed and the accurate results presented for justice to be done. 4. The basic tenets of forensic science Forensic science is the practical application of science to matters of the law. This is used in criminal law to prove the innocence or guilt of the defendant at the court of law (Houck & Siegel, 2006). It is also used in civil actions to resolve legal issues through identification, evaluation and analysis of physical evidence. Both Locard`s Exchange principle and the Principle of Individuality are used to link a particular person or object to a certain place. Forensic scientists commonly use these two principles to collect and examine evidence for criminal and civil proceedings. The Locard`s exchange principle is used by forensic scientists to collect evidence from the crime scene. It involves examination of the physical evidence that includes materials left at or collected from the scene, offender or victim (Saks & Faigman, 2008). Things such as hairs, soil, fibers, fingerprints, genetic markers, footprints and handwriting are collected for analysis. This information is then linked with the available witnesses, suspects and victims statements to establish the truth. The information is applied to the case for fair judgment. The principle of individuality assists in linking the results that are found after examining the trace evidence to a particular individual. Since it is believed that there are no two objects that are completely identical, trace evidence gathered can be linked to a particular individual(s). The principle of individuality seeks to identify uniqueness among suspects and links the findings to a particular person. This information can be used to prove or falsify the available facts in a case. Application of the Locard`s Exchange principle alone is not sufficient to link the trace evidence to a particular person. This principle only enables the forensic scientists to collect evidence that was left at the scene or taken from it but it does not link it to a specific person (Gaensslen et al, 2008). The evidence gathered can be difficult to distinguish from the rest of the objects and link to a particular person. The exact perpetrator may not be identified even after examination of the evidence. Some objects and persons are indistinguishable hence using the Locard`s exchange principle alone may not accurately link the evidence to the perpetrator. The Principle of individuality has to be applied to identify the uniqueness of the objects and persons so that they can be linked to a specific suspect. This principle establishes the difference among various objects which aids in linking the evidence accurately. Similarly, using the principle of individuality on its own is not sufficient. This principle only assists in establishing uniqueness among the objects and persons (Houck & Siegel, 2006). It enables the forensic scientists to distinguish between two or more objects and link evidence. However, this principle does not provide trace evidence to be examined. The Locard`s exchange principle must be used to collect trace evidence from the scene which are then subjected to analysis to determine the uniqueness. Without collection of the trace evidence the principle of individuality cannot be used to link a person to a scene. 5. The Incident Scene Processing of the crime scene is very important for accurate collection of evidence. There are different approaches that are used in processing the crime scene depending on the type of scene. However, there are general steps that should be taken in processing a crime scene. These include interviewing, examining, photographing, sketching and processing (Saferstein, 2007). Each of these steps should be carried out systematically to provide the required evidence. Interview is normally the first step taken in the processing of a crime scene. A forensic technician must interview the first officer to arrive at the scene and the victim to get the theory of the case. The interview should highlight what allegedly happened, the crime that took place and how it happened. This information may not be factual but it provides a base to start the investigation. The second step involves examination of the crime scene. The forensic technician examines the scene to ascertain whether the theory given by the interview is substantiated by the observation (James & Nordby, 2005). It involves identification of possible evidence such as the point of entry and exit as well as the general layout of the scene. The third step in the processing of the crime scene is taking photographs. Photographing helps to record a pictorial view of how the scene looks like and the item that can be used as possible evidence. The photographs are taken for overall views as well as items of evidence. The fourth step in the processing of the crime scene is sketching the crime scene. A rough sketch of the scene is drawn by the technician to demonstrate the general layout of the scene and identify the exact positions of the evidence or victim within the scene. Sketching is important to identify the exact situation on the ground. The last step is processing of the crime scene. The processing is done by the scene technician to provide testimonial and physical evidence that is used in a case. It is the responsibility of the technician to identify, collect and evaluate physical evidence available at the crime scene. This evidence is farther analyzed in the crime laboratory. 6. Physical Evidence The physical evidence can be used to support the case theories that were provided by the witnesses through an interview. The evidence is linked to claims raised by people interviewed to determine the truth about the crime. The physical evidence can also be used as evidence to prove that the crime actually took place and the objects collected can be used to accuse the suspect that is arraigned before the court (Houck & Siegel, 2006). The evidence can be examined to identify finer details that are used to link the perpetrator to the crime. This evidence can also be used to ascertain the exact value of damage that was caused by the crime. This information assists in quantifying the real amount of damage as a result of the crime which may be important for legal steps to be taken. Crime scene reconstruction is a discipline where one gains knowledge on various events that surround the commission of a crime (Saferstein, 2007). It involves the use of inductive and deductive reasoning, physical evidence and scientific methods. The forensic scientists may be involved in this process by evaluating the physical evidence that is available and the context of the crime scene to determine what exactly occurred and in which way it occurred. The forensic scientists can also be involved in the crime scene reconstruction to develop actions and circumstances that based on the evidence collected and examined. The evidence that is collected is normally separate and the forensic scientists can help to put the evidence together. The forensic scientists are also involved in the interpretation of the evidence in the context of the crime. They assist in understanding the meaning of various pieces of evidence and how they fit in the overall context of the scene. This paints a clear picture for people who are not experts and facilitates the legal process. 7. Trace Evidence a. Factors that influence the transfer of trace evidence. Transfer of trace evidence is influenced by the type of evidence to be transferred. Physical evidence that is tangible and portable can be easily transferred to the lab or any other place. However, other types of evidence are not portable hence they have to be examined at the scene of the crime. The size and construct of the evidence also influences its transfer. Evidence that is small in size can be transferred in large numbers as compared to huge evidence. The physical size therefore affects both the cost and means of transportation which has to be used. Care has to be taken to avoid alteration of the evidence. Another important factor is the physical form of the evidence. Some evidence are not tangible cannot be transferred from one place to another. The evidence that is delicate should be handled with care to ensure that important features are not altered. Suitable methods must be used to transfer various forms of evidence which might include liquids, solids or even intangible things. b. The concept and significance of control samples in forensic science. Control samples refer to samples with known composition, type, source and identification that are used for comparison purposes. These samples are used to ensure that the analysis is being done properly and the results are reliable. The forensic labs use control samples to ensure that the results are reliable and to eliminate incorrect results. Samples that do not contain a substance of interest (blanks) are also used in forensic labs to ensure that equipment and instruments used are not contaminated by the substance before they are used which may lead to false results. Exemplars are specific samples that are known used for comparison purposes. Bibliography MM Houck and JA Siegel, 2006. Fundamentals of Forensic Science. Academic Press,Burlington MA. ISBN 0 12 356762 9 R Saferstein, 2007. Criminalistics: An Introduction to Forensic Science. Pearson, Upper Saddle River NJ. 9th ed ISBN 0 13 224397 0 RE Gaensslen, HA Harris, H Lee, 2008. Introduction to Forensic Science and Criminalistics. ISBN 0 07 298848 7 Saks, Michael J.; Faigman, David L. (2008). "Failed forensics: how forensic science lost its way and how it might yet find it". Annual Review of Law and Social Science Schafer, Elizabeth D. (2008). "Ancient science and forensics". In Ayn Embar-seddon, Allan D. Pass (eds.). Forensic Science. Salem Press. p. 40. SH James and JJ Nordby (eds), 2005. Forensic Science: An Introduction to Scientific and Investigative Techniques. CRC Press, Boca Raton FL.2nd ed, ISBN 0 8493 2747 4