Use of DNA evidence in Courtrooms Essay Examples & Outline

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Use of DNA evidence in Courtrooms

The use of DNA evidence in courts have grown in recent years, in fact, DNA testing has over the years helped law enforcement identify as well as solve difficult crimes. DNA evidence has over the years has helped prove that most convicted people are, in fact, innocent. However, although DNA evidence can be accurate, there is often a danger of the evidence being compromised. There is a need for law enforcement to take great measures during the collection process in order not to contaminate the evidence (Humphrey, 2002). Most crime scenes often have very small samples of DNA, and consequently, any contamination of any evidence might jeopardize the identification of the criminal. DNA technology is often increasingly being used because of its accuracy and fairness that exists in criminal justice system.

Deoxyribonucleic acid often referred to as DNA contains genetic information about a particular person. It can be described as the instruction for the entire body's genetic makeup. DNA is a person. A person often has the same DNA through the whole body, and it is located in every cell of the whole body. As early as the 1980's, states had began enacting laws that required the collection of DNA samples from offenders who are convicted of certain sexual, as well as other violent crimes.

The Federal law allows the FBI to actively operate as well as maintain a national DNA database where different DNA profiles are generated from samples that are collected from people at crime scenes and can be able to be compared to DNA samples from criminal offenders and arrestees. DNA in many cases is used in two major ways. The first is often when the suspect is identified, and a sample of the person DNA compared to that found in the crime scene.

The results that come from this comparison are important as they help establish whether or not the suspect committed the crime. This type of comparison is highly accurate. However, there are cases where a suspect has not yet been identified, in these instances, the biological evidence that exists in the crime scene is analyzed as well as compared with other offender profiles in different DNA databases that exist. Crime scene evidence can also at times be linked with other crime scenes through the use of DNA databases.

The restriction fragment length polymorphism (RFLP) is an accurate as well as reliable test. It requires large DNA amounts in order for it to work. However, there have been breakthroughs in terms of DNA profiling and labs are now using tests based on polymerase chain reaction (PCR) method. This allows for the accurate testing on very small amounts of DNA that exists in crime scenes. The investigators at the crime scene can be able to collect DNA evidence from different sources, in fact, almost every biological evidence contains DNA.

However, not every sample that exists in the crime scene might contain enough amounts of DNA that will enable DNA profiling. Assuming that the investigators in the field collect as well as handle the biological evidence in correctly accepted methods, and they conduct the analysis correctly, then the DNA evidence can be argued to be extremely accurate (Hart, 2004). The chances of a person's DNA profile matching that of another person is extremely small, and it stands at around one in one billion.

In fact, as compared to fingerprinting and the testimony from eyewitnesses, that have flaws as well as inaccuracies, the use of DNA evidence in court is highly effective way to match a suspect to the biological samples that were found in the crime scene and were collected during the criminal investigation.

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, 2004). 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 1980'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. This consequently means that the person is innocent and was wrongly accused and convicted (Hart, 2004).

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. 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.

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. 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 1990's, and this DNA evidence was one of the first to be used in the criminal justice system. This was after a Vermont woman was kidnapped and raped in a semi trailer truck (Yashon, 2012).

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. After arresting Jakobetz, the law enforcement officials sent a sample DNA blood for DNA analysis. 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 250 million that the blood and semen samples could have been from somebody else other than Jakobetz (Hart, 2004).

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.S Court of Appeals adopted the lower court's decision that accepted DNA evidence in criminal trials. 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 1980'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. 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, 2000). 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 300 million and one in 500 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, 2011). 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. 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, 1996).

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, 1996). 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. 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, 1996).

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. M. (2000). Forensic DNA typing: Biology and technology behind STR markers. San Diego, Calif: Academic.
Krimsky, S., & Simoncelli, T. (2011). Genetic justice: DNA data banks, criminal investigations, and civil liberties. New York: Columbia University Press.
Yashon, R. K., & Cummings, M. R. (2012). Human genetics and society. Australia: Brooks/Cole.
Hart, A. (2004). How to interpret family history & ancestry DNA test results for beginners: The geography and history of your relatives. New York: ASJA Press.
Humphrey, J. A., & Westervelt, S. D. (2002). Wrongly convicted: Perspectives on failed justice. New Brunswick, NJ [u.a.: Rutgers University Press.
Lipson, A. S. (2008). Is it admissible?. Costa Mesa, CA: James Pub.
Connors, E. F. (1996). Convicted by juries, exonerated by science: Case studies in the use of DNA evidence to establish innocence after trial. Collingdale, PA: Diane Publishing Company.


Does the psychological profile have an effect on the jury’s decision?

Criminal profiling is an investigation that is done on criminal offenders in order to predict the actual traits of criminals. Specialists take on this investigation on the unknown criminals aiming at defining their actual behaviors (Brain, 2002). There are different methods that were applied while investigating characteristics of the criminals. It is through the aid of statistics that this investigation is made possible. Both descriptive and inferential statistical analysis methods were applied in defining characteristics of the criminals. Once characteristics of the criminal were defined, the results are seen to have an effect on the decisions that were made by the jury. The essay is a research whether the psychological profile of criminals have an effect on the decisions made by the jury (Brain, 2002).

In the research done on the influence that psychological profile have on the decisions made by the jury, there were different variables. Dependent variables were some of the instances and number of jury decisions that were made based on the criminal profiles. In the research, the jury and criminal profiles were considered to be the dependent variable while the decisions made by the jury based on the criminal profile were considered to be the independent variable (Brain, 2002).

Inferential and descriptive statistical analysis methods were used in the research. The effects that the criminal profiles have were used in the research. In addition, the relationship between the decisions made by the jury and the criminal profiles was a method that was used. Following the different decisions that had been made on criminals, it is quite clear that the criminal profiles had an influence on the decisions made by the jury (Brain, 2002). The jury was found out tom believe that the criminal profile gives a clear description of the criminal. In many instances, lawyers and judges were seen to have some expectation on the criminal profiles. Lastly, while researching on the effect that lies behind criminal profile, the number of cases that have been concluded based on criminal profile were analyzed. This analysis was aimed at getting frequencies of decisions made based on criminal profiles (Brain, 2002).

From the research carried out, an acceptable behavior was found out as the request for criminal profiling that is a request made by the jury on the criminals. This acceptable behavior that is important as it gives the judges a clear understanding of the criminal activities that criminals involve themselves in. On the other hand, the behavior of lawyers and forensic specialists concluding and making decisions based on the criminal profiles is not acceptable. According to the research carried out, criminals should face charges based on the crimes they have carried out other than their profiles (Brain, 2002).

While carrying out the research, samples of data were collected. Data collected was used in the analysis of the influence that criminal profile has to the decision made by the jury. Cases that were concluded without criminal profiling were considered as the references (Brain, 2002). This analysis aimed at concluding the research since raw data collected gave a clear interaction between the jury decisions and the criminal profiles. This instrument of data collection was used to give a comparison between the jury decisions and criminal profiles (Brain, 2002).

From the research carried out, it is clear that jury decisions and criminal profiles have a direct relationship. It was clear that cases that required criminal profiles ended up having the criminals to the cell. Therefore, psychological profile has an effect on the jury decisions.


Brain, C. (2002). Advanced psychology: Applications, issues and perspectives. Cheltenham: Nelson Thornes.