Crime scene evidence essays

The use of DNA is highly accurate, and consequently criminal lawyers in recent times are increasingly relying on the use of DNA evidence in order to prove a defendant either innocent or guilty Hart, The use of DNA evidence has also been able to exonerate a lot of innocent persons that were convicted through post conviction analysis of different biological samples. In fact, because DNA profiling and analysis did not exist until the 's, a reexamination of the evidence which was collected in older investigations often reveals DNA profile of the person that was convicted of a crime does not in any way match the DNA profile that exists from biological samples which were collected from the crime scene.

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This consequently means that the person is innocent and was wrongly accused and convicted Hart, However, it is of essence to understand that DNA evidence is not unassailable, there are errors in collection as well as the handling of samples used for the DNA profiling and analysis which can result in the exclusion of DNA evidence at a trial. The entire DNA structure often consists of billions of compounds which cannot be evaluated, in the same way; an entire fingerprint can, however, the results from DNA typing often represents a statistical likelihood.

Crime Scene Investigation & Photography 2015

The DNA typing is often not considered absolute proof of identify, in fact; a DNA non match is statistically referred to as being conclusive. However, any variation of the DNA structure often means that the DNA samples that were collected in the crime scene were drawn from different sources and, therefore, are contaminated.


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In fact, if a lab contaminates the biological sample or even uses unreliable methods, then the judge might decide to reject the DNA evidence at the trial because of its inaccuracies. In fact, when challenging DNA evidence, most defense attorneys, usually, focus on the behaviors of the forensic analysts and investigators in a bid to cast doubt in the results of the DNA profiles.

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This is as compared for the defense attorneys attacking the reliability of DNA profiling as a unit and as a whole. In fact, in recent times a well-known example of this defense strategy was used in the O. J Simpson case trial and the defense attorneys cast doubt on the reliability of the DNA evidence brought by the investigators.

One good example of DNA profile was in the 's, and this DNA evidence was one of the first to be used in the criminal justice system.

Crime scene Essay

This was after a Vermont woman was kidnapped and raped in a semi trailer truck Yashon, The police detectives identified Randolph Jakobetz, who at the time was a truck driver as the main suspect in the crime. Officers after searching the trailer found hairs that matched those of the victims. A comparison analysis was then conducted between the blood of Jakobetz and the semen that was found in the body of the said victim after the crime occurred.

FBI experts in the said trial testified that the blood and the semen that was found in the crime scene was a match and concluded that there was a chance of one in million that the blood and semen samples could have been from somebody else other than Jakobetz Hart, This served in the court as strong evidence and Jakobetz was later convicted and sentenced for thirty years in Federal prison. Jakobetz appealed the decision because the DNA profiling was unreliable and that it should be admitted in any court as evidence. It is at this time, in the first major federal decision on DNA profiling that the U.

This trial shows evidently how probabilities that are generated by DNA analysis can be used by courts as devastating evidence against any criminal suspect. Different Juries in the united states have viewed the statistical results that come from DNA profiles as being highly incriminating, and this has caused many attorneys to challenge and dispute the validity of the DNA results.

Since DNA was first established in courts in the 's, it has been the subject of controversy in the criminal justice system. Although different courts have increasingly allowed DNA analysis to be admitted as fool- proof evidence, there are doubts of the propriety of such evidence. Police officers and prosecuting attorneys are often quick in the identification of the benefits of DNA evidence in the criminal justice system.

The DNA evidence they state is more powerful than other evidences as it is readily available in many criminal investigations. Further, they also state that it is robust in that it does disappear or decay over time. Defense attorneys and other skeptics of DNA evidence strongly disagree with the school of thought held by law enforcement agencies. While they accept the scientific theory that exists behind DNA evidence, they often assert that it is not as reliable in practice as their proponents claim.

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They often cite DNA evidence being unreliable for several reasons. For example, contamination of the evidence owing to improper police procedures as well as wrongful laboratory work may lead to incorrect results Butler, There has also been criticizing of the procedures that are used in laboratories when estimating the likelihood of a DNA match.

Juries often consider these probabilities that are generated by labs- the figures such as one in million and one in million are particularly wrong because proper statistical analysis are not done to ascertain such figures. The statistical estimates of a match might be at times skewed by incorrect assumptions existing about the greater variation that exists in the population Krimsky, For example, in some population subgroups, individuals may be so genetically similar than a DNA match is more substantially readily to occur when one is comparing samples that are drawn from such subgroups.

Examples of these subgroups are often tightly knit immigrants, geographically isolated populations and several religious communities. There are times where the suspects are closely related to each other; this also presents a problem especially if the DNA samples that were found in the crime scene had some impurities.

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There is a need for more research on population subcultures and the DNA similarities that exist between them in a bid to get a better understanding of the statistical properties that exist between them Connors, No federal court has refused and rejected DNA evidence on the basis that the underlying scientific theory is invalid. However, there are some courts which have excluded the use of DNA evidence because of problems with the contamination of samples, questions that surround the significance of statistical probabilities, as well as laboratory errors.

Several states have been able to pass laws that recognize the DNA evidence as admissible when it comes to criminal cases. However, there are others that have enacted specific laws that admit DNA evidence in order to help resolve civil paternity cases.

The admission of DNA evidence is governed by two major tests and standards. First, there is the Fyre, or general acceptance standard as well as the Daubert, which is a relevancy reliability standard. The Fyre test originated from the case of Fyre v. United States which holds that the admission of scientific evidence is determined by whether there have been sufficient information and whether the method has over time gained acceptance in the particular field that it belongs Connors, The court ruled that a lie-detector test using blood pressure reading could not be admissible in court as evidence as it did not have enough support in its field and was, therefore, unreliable.


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The Daubert standard on the hand argues that any and all scientific evidence that is admitted to the court should be not only relevant but also reliable Connors, In conclusion, DNA technology is very fast becoming the method of choice in the linking of individuals with crime scenes as well as criminal assaults. The use of DNA evidence is being used in criminal trials and also in the proving of innocence amongst wrongly-convicted prisoners.

There are, however, several controversies regarding its use mainly based on the statistical significance as well as contamination of DNA by law enforcement officials.

However, DNA is currently being used in courts as a powerful tool of linking individuals with crime scenes, as well as paternity and identity cases. Butler, J. San Diego, Calif: Academic. Krimsky, S. Genetic justice: DNA data banks, criminal investigations, and civil liberties. New York: Columbia University Press. Yashon, R. Human genetics and society. Hart, A. Crime scene search is the investigative and operational activities intended to examine the place of crime in order to establish what had happened and identify the responsible person.

Crime scene evidence collection

The discovered traces and other evidences might help to draw the conclusions find out relative mechanism and circumstances of the case. Thus, the quality of the inspection procedure can directly influence the course of the investigation since the information obtained at the crime scene may be of evidentiary natural. The main reason for conducting the survey is a disclosure of a crime. The investigator must find out what was an assault, when and where the criminal act was committed. He has to clear up the purpose, motive of the crime and the person of the offender. In addition, it is necessary to establish the nature and extent of the damage, as well as the causes and conditions that contributed to the crime.

The crime scene is the area where the crime was committed or if any signs of offense were discovered. However, the pieces of evidence can be found beyond the crime scene, as well. Consequently, successful investigation requires both thorough indoor and outdoor inspection. Arrival to the crime location must be done as soon as possible. The first step, which the police authorities should do on arrival, is to establish a restricted outer perimeter by using a rope or a barrier for keeping onlookers away from the indicated area.

Police barricades and guards are to help with securing the scene, as well. The manner of examination and subsequent search of the crime scene should be done carefully and methodically. Law enforcement officers should be the first coming to the crime scene and must start the observing process with a great care, in order to keep all evidence in its original and untouched state.

The crime scene investigators have to ascertain the proceedings of a search process before collecting the evidence. An operation plan presenting an orderly and methodic approach of discovering and collecting evidence should be developed in the beginning of an investigating process. Its purpose is to define the resources, equipment and assistance required for the process. The initial steps in the crime scene investigation can be regarded as a Scene Recognition stage. The other equally important moment of an organized approach for the location search is the Scene Documentation.

Its function is to present consistent images of the crime scene through an application of written notes and reports, videography, photographs and sketching. As it turns out they need you to help them at the scene of a crime that took place in an office building downtown. You agree to head downtown right away.