Since its introduction in the United States in 1987, the use of forensic techniques analyzing deoxyribonucleic acid (DNA) has evolved into a standard form of evidence in criminal proceedings (Calandro, Reeder, & Cormier). There are at least three major ways that DNA forensics can be utilized in combating crimes. First, it can act as evidence of the presence of a suspect at the scene of a crime, or for certain crimes that can leave DNA evidence such as rape, even stronger evidence in support of guilt. Second, DNA forensics can be utilized to help solve older crimes that have gone cold, where materials potentially containing DNA are available for analysis. Third, DNA forensics can help prevent future crimes by solving current cases that would not have been solved, thus removing a criminal from the streets before the future crime is committed. (Department of Governmental Studies and Services, WSU, 4-5). Thus, in at least these three ways DNA forensics has had an impact on the criminal justice system.
When DNA forensics are used as evidence to convict a criminal, the form of testing that is used must provide results having certain characteristics. The primary characteristic needed is confident identification. DNA forensics used for identification relies upon differences in DNA sequences between individuals at specific sites generally called markers. The more markers that are evaluated, the more confidence there is in the results. A type of marker now used in DNA forensics is called a short tandem repeat or STR. The Federal Bureau of Investigation (FBI) has a set of 13 STR, or core loci that are used in the Combined DNA Index System (CODIS) database (Butler, 253). Additionally, other STR sites can be tested to decrease the random match probability. A decreased probability of a random match increases the confidence in the identification provided by a match. For example, STR tests are now available that have 21 markers on autosomal (non-sex) chromosomes and 23 male specific markers, which significantly increases the ability to differentiate individuals (De Ungria).
A limitation on the applicability of STR data is the availability of reference sequences within searchable databases. As of April 2013 there are approximately 10,305,200 profiles within the CODIS database. The FBI estimates that as of that date searches have resulted in over 207,800 hits, assisting in more than 199,200 investigations (Federal Bureau of Investigation). It should be noted that smaller countries, such as England, have had greater successes using DNA forensics because they have been able to collect a higher percentage of the total population within their databases (Department of Governmental Studies and Services, WSU, 39).
When DNA forensics is used as evidence in solving a cold case, other issues concerning the methodology arise. Using DNA that has been stored for long periods of time, often in less than ideal conditions, can impact what form of DNA forensics is used. In cases such as these, it may be less important to have identification, but instead the focus is on exclusion. Exclusion is used to rule out a particular individual from committing the crime. This is often the goal in prison release program such as the Innocence Project, where those involved seek to free persons who were wrongly convicted at least in part because of the lack of DNA testing availability at the time (De Ungria). For exclusion results, a type of test that can be used is called DQA1. Although the test is not very discriminating, as it only contains 8 markers, it can work on very small amounts of DNA, which is useful for cold case samples which can still be very small amounts, even after amplification using PCR (polymerase chain reaction) (PBS, Nova).
A final major use of DNA forensics in criminal justice is the prevention of crimes. Studies on recidivism, or measuring the amount of repeat offenders have that they have a significant impact in the amount of crime that is committed. So an offender who is not caught quickly and remains free could commit more crimes. DNA can be used to prevent these crimes from occurring, but the system must be efficient. The DNA must be commonly collected, processed effectively, and completed in a timely manner and there must be an effective DNA database. But the results are potentially very valuable. A study done in 2003 examined specific cases from nineteen states and concluded 100 serious crimes could have been prevented if the DNA available from those cases had been used effectively (Department of Governmental Studies and Services, WSU, 47-66).
There can be no question that DNA forensics has had a major impact on the criminal justice system since its introduction in the United States in 1987. Specifically, the results of DNA testing can be used to convict those accused of crimes, to exonerate those who are wrongly accused of crimes, and to prevent crimes from happening at all. As the databases grow and the testing becomes more sensitive, the usefulness of DNA forensics will only increase.
Works Cited
Butler, John. “Genetics and Genomics of Core Short Tandem Repeat Loci Used in Human Identity Testing.” Journal of Forensic Science. 51, 2006, 253-265. Web. 19 June 2013.
Calandro, Lisa, Dennis Reeder, and Karen Cormier. “Evolution of DNA Evidence for Crime-Solving – A Judicial and Legislative History.” Forensic Magazine. 6 January 2005. Web. 19 June 2013.
De Ungria, Maria Corazon. “Forensic DNA Technology: A powerful tool for judicial reform.” 24 January 2013. Web. 19 June 2013.
Division of Governmental Studies and Services, Washington State University (WSU) and Smith Alling Lane, P.S. “National Forensic DNA Study Report.” 12 December 2003. Web. 19 June 2013.
Federal Bureau of Investigation. “CODIS-NDIS Statistics.” Laboratory Services. FBI.gov. April 2013. Web. 19 June 2013.
Public Television System. Nova. “Forensic DNA Analysis.” From The Killer’s Trail. PBS.org. 26 September 2003. Video on Web. 19 June 2013.
