Brief History of DNA and Its Importance to Criminal Investigations

Brief History of DNA and Its Importance to Criminal Investigations

Deoxyribonucleic acid, DNA for short, is the foundation for all life on Earth. DNA is a substance located in a cells nucleus, composed of various proteins, carbohydrates and elements wound into a helix-shaped strand. The stand's main purpose is genetic coding, which determines what trait a life form possess and what traits are passed on to further generations. Hair and eye color, height, gender and skin pigmentation are examples of genetic traits that DNA determines in humans. From a criminology standpoint, this coding can help an investigator identify whether a individual suspect has committed a crime or clear his or her name.

Modern DNA techniques would not be a reality without the hard work of a handful of individuals. One of these individuals was a 19^th century Roman Catholic monk named Gregor Mendel, who is posthumously known as the “Father of Modern Genetics.” Educated at the University of Vienna, Mendel began to experiment with pea plants in 1857. He grew thousands of plants during the course of his experiments, which lasted eight years (Mandal 2012). Mendel noticed that certain traits came out more often than others, and that crossing plants with different traits could affect the resulting offspring. These results established the rules of heredity, which scientificly determines the likelihood of a being inheriting certain traits from each parent. This is now known as the law of Mendelian inheritance.

In the decade following Mendel's pea experiments, a Swiss scientist named Friedrich Miescher began an experiment of his own. While he started with lymph cells, the technology of his day forced Miescher to switch to pus cells, as they were easily obtained in high numbers at the local hospital. Mescher noted that the cells reacted differently to different salt solutions, gaining a curious result from one in particular. According to Devor, “Meischer was convinced that he had discovered a new type of cellular material and went on on to determine where in the cell it came from. He noted that cell nuclei were particularly affected by the weak alkaline solutions” (2005 Page 2). In subsequent experiments Meischer noted that the substance he had viewed was common in all human cells, no matter where in the body they were taken from. The substance, which Meischer called nuclein, would eventually be called nucleic acid. “This substance was found to exist only in the chromosomes” (Mandal 2012).

Throughout the twentieth century scientists hypothesized how DNA was physically structured. One of the first models was made in 1912 by Steudel. In the 1920's, a Russian-born chemist named Phoebus Levene began to construct his own model. It took him several years, but Levene eventually identified the components of a DNA molecule: sugar, phosphate, and four bases; the four bases are Adenine, Cytosine, Guanine, and Thymine. Levene concluded that “the components of DNA were linked in the order phosphate-sugar-base. He said that each of these units is a nucleotide and suggested the DNA molecule consisted of a string of nucleotide units linked together through the phosphate groups” (Mandal 2005).

Despite his discovery, Levene was unable to deduce DNA's proper structure. That advancement would not come until 1953. That year James Watson and Francis Crick, building upon the work of their predecessors, showed that DNA had a double helix shape. Rungs made from the bases connected the helix. According to Mandal, the pair also noted that by pairing Thymine with Adenine and Guanine with Cytosine, DNA took on a uniform appearance (2005).

From DNA's discovery until the late nineteen-seventies there was very little criminal investigators could do with DNA found at a crime scene. At most they could pinpoint the suspect's blood type. This was changed in by Alec Jefferys, a geneticist at the University of Leicester. According to Newton, “Professor Jeffreys's plan was to use the primitive gene detection methods of the time to look at the structures of genes and understand inherited variation – the variation between people. An early outcome of this research was one of the first descriptions of a restriction fragment length polymorphism (RFLP) ” (2004). This was a minor breakthrough, as it showed variation occurred but not what they were. It was also time consuming, as RFLP's were difficult to find with technology of the time. Jeffreys continued his research in hopes of finding a more reliable technique. It took Jeffreys awhile, but he eventually came up with a technique “where a short sequence of DNA was repeated many times in a row” (Newton 2004). The technique was eventually called tandem repeating DNA. It was messy, but after a few months of tinkering Jeffreys had the first clear DNA fingerprint.

This advancement soon gave Jeffreys the distinction of being the first scientist to use DNA fingerprinting in a criminal investigation. In November 1983 a young woman named Lynda Mann was found strangled along a foot path she had been walking down the night before. Investigators noted Mann had been sexually assaulted and semen was collected from her body. A blood test determined that her killer had type A blood, which occurred in one out of every ten English men at the time (Dolan, 2012). Detectives soon ran out of leads and the case went cold. Three years later another murder occurred along the same foot path. The victim, Dawn Ashworth, was found in virtually the same condition as Mann. The identical modus operandi lead detectives to conclude that Ashworh and Mann had been killed by the same individual. Unlike with the first case, it did not take police long to locate a suspect. Seventeen-year old Richard Buckland was brought in for questioning when police were informed he was talking about the case in a manner that only the perpetrator would. Buckland denied any involvement, but after several hours of questioning he confessed, but only to the Ashworth murder.(Dolan, 2012). Because of the similar modus operandi, police ignored Buckland's denial.

This is where Jeffreys name first enters the case. By this point his work had advanced to the comparative DNA level, starting with paternity results. The detectives were aware of this, as the University of Leicester was not that far away from where the murders had occurred. Semen samples from both cases and blood from Buckland were soon sent over to the lab. Police were given good and bad news upon the tests completion. While they were correct and believing that both murders were committed by the same individual, the DNA from the semen did not belong to Buckland. Further police work and another round of DNA tests lead to the arrest and conviction of the perpetrator, Colin Pitchfork. (Dolan, 2012). It is fitting that the first use of DNA in a criminal case would clear rather than condemn a suspect, especially one who would have most likely been convicted without such evidence.

In a little over a century, DNA research has come a long way. As science continually advances, so does the way in which DNA is used and the methods scientists use to extract the substance. What took a large sample in the eighties can now be done with very little. It makes one wonder what the future holds for DNA research and its use in criminal investigations.

References

1.Dolan, Michael (writer), & Dahl, Jay (director). (2012). “DNA Profiling”. Lee Anne Gillan (associate producer), Forensic Firsts. Washington, D.C.: The Smithsonian Channel.

2.Mandel, Ananya, M.D. (2012). “History of DNA Research.” Retrieved October 1^st, 2014,

from http://www.news-medical.net/health/History-of-DNA-Research.aspx

3.Newton, Giles (2004). “Discovering DNA Fingerprinting.” Retrieved October 3^rd, 2014, from

http://genome.wellcome.ac.uk/doc_wtd020877.html