DNA Typing The discovery of the structure of DNA opened the realm of DNA technology and changed the way in which crimes can be solved. This is due to the fact that many criminals often unwittingly leave their DNA at crime scenes and/or the DNA of victims is carried away on the clothes of their assailants (Saferstein, 2015). Thus, by using DNA it is relatively easy to place individuals at crime scenes and discover key evidence.
Before the 1980s, the courts primarily relied on testimony and eyewitness accounts as the main source of evidence (Newton, 2008). Notoriously unreliable, it comes as no surprise that these techniques have since faded away due to the reliability of DNA typing. DNA typing, also called DNA fingerprinting or DNA profiling, is the use of DNA evidence for identification (Panneerchelvam & Norazmi, 2003). The primary purpose of DNA typing is to obtain DNA from a biological sample and compare this to profiles obtained from a crime scene, individual or database.
DNA typing can be used for many different crimes and circumstances including rape, assault, murder, body identification, and establishing parentage (Butler, 2012). The first mentions of DNA typing can be traced back to the work of English geneticist, Alec Jeffreys. In 1985, Alec Jeffreys was attempting to trace the genetic markers between members of the same family (Curran, 1997). He eventually developed a technique to measure the difference between DNA sequences, effectively allowing for human identity tests.
Based on Alec Jeffreys’ work, the first use of DNA typing can be traced back to a criminal case in 1986, where it was used in order to determine the perpetrator of a sexual assault and murder (Piven, 2014). By comparing blood samples of over 4000 men to the semen found at the crime scene, the use of DNA was able to accurately identify the murderer. In the years following similar groundbreaking cases, the admissibility and examination of DNA evidence has been widely accepted by both the legal and scientific community (Hedman, et al. 2009). DNA typing can make use of any specimen that contains DNA, although some are more useful than others. The more useful sources include blood, semen, vaginal fluid, nasal secretions and hair with roots (Roewer, 2013). In the use of blood stains, it is the DNA from the white blood cells that is used: mature human red blood cells do not have nuclei and so contain no DNA. Semen normally contains large amounts of DNA in the sperm cells, which makes it very useful for DNA typing, especially in cases of sexual assault (Butler, 2012).
It is also possible to obtain DNA from evidence such as urine, faeces and dead skin cells, though this is often classed as a poor source due to the lack of intact cells and high levels of contaminants preventing successful analysis (Butler, 2012). Specialists who conduct DNA analysis are referred to by several titles, including: crime laboratory analyst, forensic examiner and forensic scientist. Regardless of the title, DNA analysts must meet specific educational and training requirements (Figarelli et al. , 2013).
The education standard requires at a minimum a bachelor’s degree in biology, chemistry, or a forensic science related area. In addition, the DNA analyst must reach certain guidelines in regards to coursework covering subject areas like biochemistry, genetics, molecular biology, and statistics as it applies to forensic DNA analysis (Figarelli et al. , 2013). Obtaining DNA evidence is only the starting point of DNA typing. The true value lies in the outcome of the analysis, which can be performed by different techniques, the most successful being the short tandem repeat (STR) analysis (Hedman, et al. 2009). STR analysis works to examine individual areas in DNA. The variable nature of the STR regions that are analyzed are said to “intensify the difference between one DNA profile and another” (NIJ, 2012, p. 1). In criminal investigations, there are thirteen regions that are analysed and compared to establish profiles. In fact, DNA databases used at the government level involve the sequence of these thirteen regions (NIJ, 2012). For instance, the likelihood that any two individuals (except identical twins) will have the same 13-loci DNA profile is virtually impossible.
Another analysis technique is mitochondrial DNA (mtDNA) analysis which allows DNA profiles to be developed from evidence that may not be suitable for STR analysis. Essentially, MtDNA analysis examines DNA found in a different part of the cell, the mitochondrion. As such, evidence – such as hair shafts- that are not responsive to STR testing may yield results if mtDNA analysis is performed (Hedman, et al. , 2009). Strengths of DNA Typing
DNA typing is a staple of modern crime investigations due to its ability to determine if distinctive patterns in the genetic material found at a crime scene matches the DNA in a potential perpetrator with high accuracy (Taupin, 2014). It can provide both exculpatory and inculpatory evidence. Both types of evidence are equally important in criminal justice, particularly when a person’s freedom is on the line: exculpatory evidence includes any proof of an individuals innocence, while inculpatory evidence provides proof of guilt (Buckleton, 2016).
Even years after a crime occurs, DNA analysis has proven itself to be the chief piece of evidence in many criminal cases. For example, Timothy Wilson (also known as “The Southside Slayer”) is best known for being the first to be identified and convicted as a result of DNA evidence. He was sentenced to death after DNA linked him to several rapes and murders in the area (Shaer, 2016). Another example is the solving of the famous Boston Strangler case, which was considered as a mystery for almost fifty years. Only through the use of DNA evidence could the olice have brought closure to the case and linked the killer to the victims (Goldhill, 2014). Not only has DNA typing allowed the police to apprehend perpetrators, it has also been vital in discovering innocence for incarcerated individuals. There are many cases that innocent people are incarcerated, or even executed, because of errors in the criminal justice system (Taupin, 2014). Some of these cases happened when DNA testing was not available, and others were caused by human and systematic errors. For example as Dr.
Michael Naughton, founder of the UK Innocence Project, a nonprofit advocacy group that works to free the wrongly convicted, said,” People think that miscarriages of justice are rare and exceptional … But every single day, people are overturning convictions for criminal offences. Miscarriages of justice are routine, even mundane features of the criminal justice system” (Goldhill, 2014, p. 1). The frequent and common instances of errors in the criminal justice system only further highlight the benefits of using DNA evidence.
For example, DNA evidence has saved the lives of those on death row and freed others from long prison terms. Since the first convicted inmate was exonerated using DNA evidence in 1989, there have been over 300 DNA exonerations nationwide, with the vast majority since ending in freedom for the convicted (Piven, 2014). In addition to its potential to free the innocent, DNA testing can help identify a crime’s true culprit as nearly half of DNA exoneration cases lead to someone other than the falsely convicted individual (Goldhill, 2014).
Furthermore, it is important to understand that DNA typing provides irrefutable evidence in the sense that the evidence itself is objective and free from the prejudices or injustices present in the criminal justice system (Newton, 2008). As Lawrence Kobilinsky said, “DNA testing is the ‘the gold standard for proof that, if produced, can trump other types of evidence” (Piven, 2014, p. 1). For instance, research shows that biases against those with criminal records often lead to suspicion, stops and interrogations by police officers.
One such example is Thomas McGowan, who was falsely convicted of rape and exonerated through DNA testing. He had prior police contact because of a minor traffic violation. McGowan’s mugshot from that arrest was entered into a photo lineup and he was wrongly identified by the victim (Goldhill, 2014). Many similar cases indicate that the criminal justice system is marked by injustice and the discrimination manifests itself through racial profiling, police misconduct, indigent defense, jury selection and more.
Wrongful conviction cases found through DNA evidence reveal these biases well— both in individual cases and systemically (Grimsley, 2013). As such an advantage of DNA typing is its reduced possibility of human error and subsequent objectivity. Another strength of DNA typing is that, when performed properly by qualified staff, it is considered as one of the most powerful tools for the individualization of bodily substances. This is because random match probabilities are often so low as to accurately pinpoint an individual as the source of a bodily substance to the exclusion of all others (Taupin, 2014).
In fact, the National Research Council, in its influential 2009 report, said that, “No [other] forensic method has been rigorously shown able to consistently, and with a high degree of certainty, demonstrate a connection between evidence and a specific individual or source” (N. A. S, 2009, p. 1). Also, multiple testing systems are available to forensic scientists for use under various circumstances, thereby increasing the likelihood of successfully generating DNA profiles.
Furthermore, as accuracy rises and costs drop, DNA analysis is becoming increasingly widespread (Newton, 2008). DNA evidence is relevant not only for crime investigations, but can also be extensively applied to others activities from establishing paternity identifying remains to directing captive breeding programs in zoos (Goldhill, 2014). These above mentioned facts clearly indicate the usefulness of DNA typing and the integral role it can play in the criminal justice system.
