DNA Analysis in Forensics: History, Uses, and Future

Introduction

DNA analysis, also known in its early years as DNA fingerprinting, emerged in the latter half of the 20th century through breakthroughs in scientific investigation. It has been used in forensics ever since and is defined as "comparison of the DNA in a person's nucleated cells with that identified in biological matter found at the scene of a crime or with the DNA of another person for the purpose of identification or exclusion" (Roewer, 2013). DNA analysis is now a common tool of criminal justice, used in forensics to help identify suspects and, in some cases, to clear others. This paper provides the history of DNA analysis, examines how it is used today, and considers what the future holds for this tool in the field of criminal justice.

History of DNA Analysis

Alec Jeffreys made the first discovery of the method of DNA analysis in the mid-1980s in the UK (Jeffreys, Wilson, & Thein, 1985). Jeffreys was working on identifying "simple tandem-repetitive regions of DNA (or 'minisatellites')" that occurred in the human genome sequence and were unique to individuals (Jeffreys et al., 1985, p. 76). He developed a method of identifying "sets of hypervariable minisatellites to produce somatically stable DNA 'fingerprints' which are completely specific to an individual (or to his or her identical twin)" (Jeffreys et al., 1985, p. 76).

In 1987, DNA analysis was used in a case to bring to justice Colin Pitchfork, who confessed to raping and murdering two girls in an English village in the 1980s. Trace DNA from semen samples obtained at the scenes of the crimes was analyzed, and Pitchfork's DNA profile was matched to the DNA from the crime scene. It was the first time in history that DNA analysis was used in a forensics case, and its arrival had a spectacular effect — particularly among interdisciplinary studies — as the utility of DNA fingerprinting in criminal justice was evident. It had allowed for the exoneration of one suspect and led to the conviction of the actual perpetrator.

In the 1990s, DNA analysis began receiving a great deal more attention as the application of this type of analysis stretched far and wide. Jeffreys' original system was re-engineered to be simpler, automated, and more effective. DNA fingerprinting became known as DNA profiling, and the process of DNA analysis became a staple of forensics laboratories all over the globe. However, DNA analysis is only one step in the criminal justice process, and as the O. J. Simpson case showed, there are ways to prevent DNA evidence from being accepted in court or regarded by a jury — especially if doubts about chain of custody can be raised. Two cases in particular helped to illustrate the limitations of DNA analysis and its applicability in criminal justice: the case of People v. Castro in New York in 1989, in which the Court found that DNA analysis was more useful for exclusion than for inclusion, and the case of Amanda Knox in Italy in the 2000s (Roewer, 2013), which similarly examined the limitations of DNA analysis in pinpointing the exact identity of a perpetrator.

As DNA analysis is still relatively new to the field of criminal justice — being under four decades old — there is much room for growth, both as a professional tool that can be reliably used in criminal investigation and in terms of social acceptance. DNA analysis has played a large role in high-profile criminal cases that have caught public attention over the decades, and this has not always had positive ramifications for the field. As in any type of profiling, there is more art to it than science; some DNA analysts view the field as something that should play a supporting role in investigative police work rather than being relied upon as a primary source of evidence. DNA analysis is not yet completely exact, nor does it offer exact methods of identification, given that it still draws on a relatively small database and not everyone's DNA is on record. Were everyone to contribute to a DNA database, the use of DNA analysis in gathering evidence would likely be far more effective and broadly accepted.

How DNA Analysis Is Used Today

Today, DNA analysis serves as a helpful indicator — a clue — that investigators can use to help reconstruct the scene of a crime. While DNA analysis has clear uses in some cases, such as where an accused person may attempt to prove innocence through DNA evidence (or a lack thereof), there are plenty of instances in which DNA evidence can be manipulated, faked, or completely misunderstood (Austin, 2015; Worth, 2018). The limitations of DNA analysis, however, do not prevent its applicability in the criminal investigation process, as a case from 2002 in Europe illustrates.

In 2002, a woman in Berlin was attacked in her apartment building and nearly killed. The medical community was able to save her life, and the account she gave investigators described a single male attacker who entered her room and assaulted her. Blood was found on a glass used to smash the woman's skull, as well as on two towels and a baseball cap. The tenant next door was first suspected, as the DNA analyzed revealed a pattern consistent with his own. However, the tenant had not been in town at the time of the attack and had a solid alibi. Suspicion then fell on one of two other men who had been staying in his flat at the time. The two men were related, and police used haplotyping to obtain more information about the suspect. Haplotyping was able to show that the population from which the suspect came was not African but rather South European. Police then located the original tenant and used his help to find one of the other two men who had been staying in the flat. It turned out that this man was the uncle of a younger man — his nephew — and because of that relationship he was unwilling to speak. However, investigators had data from their DNA analysis that led them to believe the nephew was likely the perpetrator, and they used their DNA evidence to help motivate the uncle to reveal what he knew. In other words, the DNA analysis did not prove anything conclusively, but it provided one more clue that investigators could use to narrow the pool of suspects to a single source and leverage that information to draw out additional testimony from someone close to the suspect. In the end, the nephew was arrested, and it emerged that he had already committed another violent theft (Roewer, 2013). In this example, DNA analysis helped turn the tide of an investigation.

Conclusion

DNA analysis got its start in the 1980s in England when Jeffreys identified a method for linking the human genome sequence of blood samples to individual persons and distinguishing between individuals based on their DNA. This had a tremendous impact on the field of forensics, as it became clear that DNA analysis could help in exonerating and indicting suspects — as happened in the Pitchfork case in England. Over the years, that method has been refined and new DNA testing technology has been developed to support the automated reading of DNA samples. Today, DNA databases are being created to facilitate the more efficient use of DNA analysis in criminal investigations, and the coming decades promise even greater advances in the speed, accuracy, and global reach of this essential forensic tool.

References

Austin, E. (2015). DNA evidence can be faked. Retrieved from https://www.forensicmag.com/news/2015/02/dna-evidence-can-be-faked

Jeffreys, A. J., Wilson, V., & Thein, S. L. (1985). Individual-specific 'fingerprints' of human DNA. Nature, 316(6023), 76–79.

Roewer, L. (2013). DNA fingerprinting in forensics: past, present, future. Investigative Genetics, 4(1), 22.

Worth, K. (2018). Framed for murder by his own DNA. Retrieved from https://www.themarshallproject.org/2018/04/19/framed-for-murder-by-his-own-dna