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Dna Use in Criminal Investigations

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The technique of deoxyribonucleic acid (DNA) testing was first used in the late 1980's to convict a Portland, Oregon man of raping and impregnating his 13-year-old daughter. Scientists were able to analyze DNA from both the man and the fetus, which had been previously aborted, and the results were conclusive. This provided concrete evidence against the man, who eventually confessed to the crime. Since the discovery of DNA in the 1980's the use of DNA in criminal investigations has proven to be an extremely useful tool and has grown drastically in recent years and helped criminal investigators solve crimes and identify criminals. DNA has also assisted criminal investigators in proving the innocence of many wrongly convicted individuals. This research paper will attempt to explain what DNA is, the effectiveness of DNA testing, address legal and ethical concerns, as well as, discuss the advantages and disadvantages of DNA testing in criminal investigations.

What is DNA?

Deoxyribonucleic acid most commonly referred to as DNA is the hereditary material in humans that is passed from adults to children during the reproduction process. DNA is found in the nucleus of the cells in the human body with the exception of red blood cells. Nearly every cell in a person's body has the same DNA and contains the biological instructions that make each person unique, except in the case of identical twins because identical twins carry the same DNA (Anjaria. n.d.).

Since each person's DNA is different scientists are able to distinguish the DNA of one individual from another. This can be done through the collection of DNA samples. DNA samples can be found in a person's skin cells, clothing, hair, semen, blood, saliva, perspiration, and fingerprints, and can be retrieved from items such as cigarette butts, clothing, hairbrushes, toothbrushes, footwear, and many other sources. Due to the many sources that DNA evidence can be found in and the ability to identify an individual through DNA testing; DNA collection has become a very powerful tool in criminal investigations. DNA evidence has sent many people to jail and also played a vital role in exonerating individuals who were falsely convicted. There is a long list of individuals whom have been convicted with DNA as one of the primary sources of evidence against him or her.

DNA Evidence in Criminal Investigations

As is the case in every crime scene, the first step taken by investigators upon arriving at the scene of the crime is to seal off the crime scene to prevent unauthorized persons from entering the area and contaminating the evidence. DNA evidence is collected and used to connect a suspect to the crime scene or identify the suspect and/ or victim of a crime. It is extremely important that criminal investigators do not contaminate any DNA evidence at the scene of the crime, because "a single hair or drop of sweat from an unprotected person could leave an unknown DNA sample at the scene ("Dna"). Investigators themselves must also be sure not to contaminate any evidence during analysis and maintain a strict chain of custody, as well, because just one break in the chain of custody can be reason to question the "integrity of the chain of custody" and nullify the claim that the item of evidence is relevant to the crime (Ogle, 2011, pg. 24).

Once DNA evidence has been collected it will be sent to a laboratory for a forensic DNA analysis. "Forensic DNA Analysis is a process of identification and evaluation of biological evidence in criminal matters using DNA technologies" ("Quality assurance standards," n.d). There are two types of DNA that Forensic Analysts can use in criminal investigations; mitochondrial and short tandem repeat (STR) DNA.

Mitochondrial DNA is "found in the cytoplasm of the cell and can be found in hair shafts" ("Dna"). This type of DNA also runs along the maternal line meaning siblings share the same mitochondrial DNA with their mother, grandmother, great-grandmother and so on. "All mothers have the same mitochondrial DNA as their offspring, because the mitochondria of each new embryo comes from the mother's egg cell. Comparing the mitochondrial DNA profile of unidentified remains with the profile of a potential maternal relative can be a useful and important technique in cases such as missing-person investigations" (Mansfield, 2009).

The second type of DNA, STR DNA is "found in the nucleus of the cell and is the most common form of DNA used in criminal investigations. Only a very small biological sample is required to test for STR DNA and an analysis can provide very discriminating results with a probability result of one in three hundred billion" ("Dna," n.d.). The odds of two people carrying the same DNA profile can be as high as one in a billion (Mansfield, 2009). These odds explain why DNA evidence has proven to be extremely effective in criminal investigations.

Effectiveness of DNA Testing

DNA testing can effectively identify an individual who was at the scene of a crime. "Compared to fingerprinting or eyewitness testimony, which both have inherent flaws and inaccuracies, DNA evidence is a highly effective way to match a suspect to biological samples collected during a criminal investigation" ("How dna evidence works," 2012). Locard's Exchange Principle; which states that that every encounter or contact leaves a trace no matter how slight the encounter may have been helps one understand how DNA can be effective (Ogle, 2011). When an individual commits a crime it is near impossible for the individual to prevent leaving some form of trace evidence behind. It could be a hair, fingerprint, small drop of blood, or other forms of trace evidence that are not visible to the human eye. This evidence can be found and analyzed by forensic analysts to effectively identify the individual who was at the scene of the crime. However, "matching DNA from a crime scene to DNA taken from a suspect is not an absolute guarantee of the suspect's guilt" (Harris, 2011). Matching DNA from a crime scene to a suspect or person of interest may prove that the individual was at the scene of the crime, but DNA alone cannot be relied upon to prove the suspect committed the crime. There must be additional evidence that coincides the DNA evidence. For this reason there are both advantages and disadvantages to DNA testing in criminal investigations.

Advantages of DNA Testing

The primary advantage to DNA testing in criminal investigations is it provides investigators with the ability to prove that a suspect was indeed



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