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 19th
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 1st,
2014,
from
http://www.news-medical.net/health/History-of-DNA-Research.aspx
3.Newton,
Giles (2004). “Discovering DNA Fingerprinting.” Retrieved
October 3rd,
2014, from
http://genome.wellcome.ac.uk/doc_wtd020877.html