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Unit 13 Assignment D - DNA Database
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Forensic DNA DatabasesUnit 13
Assignment D
DNA databases are important in linking physical evidence to offenders with their crimes.
They can sometimes be the defining factor as to whether an offender is convicted or not. In
this assignment, I will be evaluating the use of the DNA database, its history, and overall
impact of cases, as well as the legalities involving the use of the database.
The History of the DNA Database
The creation of the DNA database occurred in 1995. It is officially known as the UK National
Criminal Intelligence DNA Database, and is still continuing today, with 3.5 million DNA
samples added between 2005-2020, and now ‘7.1 million’ (1) (Home Office, 2024.) samples
as of 2023. Initially, before the DNA database was created, forensic investigators could go
and take blood samples from doctors, however DNA technology was still not the most
efficient, and consent still had to be granted.
Within the database, it holds two types of DNA profiles, this being individual DNA, from those
who have been arrested, and DNA from crime scenes, which includes things like hair and
saliva samples.
The DNA Database is crucial and an important part in forensic investigations, as it means
unsolved cases can be solved due to DNA data being on the system, and can be helpful in
that regard in the fact it can help provide closure to families.
DNA Data within Forensic Investigations
DNA Data is vital within the elimination and identification of suspects and individuals. This is
done through something called Short Tandem Repeat Loci (STR), this involves extracting
DNA from a sample, and then analysing and looking for repeated base pairs. In the UK they
look at 10 pairs, (2) Doing this allows for individual samples to be compared to look for
matches. It also includes pairs of letters - either XX or XY - to denote gender, this allows a
person to be easily identified if DNA is left behind at a crime scene. In order to extract
samples, capillary electrophoresis is used, which gives distinct patterns and graphs on DNA
data, which are the repeated base pairs forensic scientists look at when creating the DNA
profile. This is also effective as it can be done with such a small amount of cells, so if a
sample isn’t too big, it can still be used.
The use of DNA Data proves so vital and useful in the example of the case study involving
Ronald Cotton, a man who has been incarcerated for 10 years before he was exonerated
using DNA evidence. This occurred after an eyewitness to a crime of sexual assault and
burglary was flawed, and lead to Cotton being sentenced in January of 1985. This changed
in 1995, when semen found at the crime scene was sent for DNA testing, this returned no
match for Cotton but yet another man who was already convicted in prison, Bobby Poole.
Cotton was able to be exonerated and all charges against him dropped. This case shows the
importance of DNA testing in identifying and even exonerating wrongfully convicted
, individuals. DNA testing allowed for the misjudgement of justice to be corrected, as well as
emphasised the further need for DNA evidence to prove someone’s guilt. Without DNA
analysis, Robert Cotton would have spent life in prison for a crime he did not commit. (3)
The Integrity and Validity of DNA
It is vital that DNA does not become contaminated, and the integrity and its reliability to be
used in a court of law remains. This can also be shown in the case of Sean Hodgerson, a 57
year old who was sentenced to life in prison, when his blood sample shared a match with
multiple other men. This evidence was used to convict Hodgerson in 1979, however in the
findings of the original semen sample and DNA analysis found Hodgerson was not in fact the
murderer of 22 year old Teresa de Simone. This was because the analysis of the STR loci
within the case enabled forensic investigators to identify his genetic profile, with certain
repeated base pairs not identified in the actual offenders’ semen sample. This was then able
to determine and exonerate Hodgerson. Without the DNA database coming into fruition, this
exoneration would never have occurred. Further proving the usefulness of the DNA
database's ability to identify individuals. (4)
DNA contamination is clearly defined as “the undesirable introduction of DNA, or biological
material containing DNA, to an item/exhibit or sample during a forensic medical examination”
(Gov.UK, 2024.), (5) this can happen through a variety of reasons, such as through direct
contact such as saliva from the forensic investigator being found on the sample and
indirectly through transfer by the means of gloves or other materials. This risk of
contamination can be minimised through use of PPE (personal protective equipment) when
gathering evidence from a scene or during analysis and cleaning surfaces which may be
exposed to other DNA samples. This is proven significantly in importance in the case of
Meredith Kercher, who was found murdered in 2007. During the search of the crime scene,
PPE failed to be worn, resulting in mass cross contamination, such as hair strands and or
saliva from the investigating police officers being found on the scene. Therefore, when DNA
analysis was done, insufficient evidence of convicted Amanda Knox’s DNA was found, due
to the failure to package evidence correctly as well as contamination. Such as the STR loci
found and the genetic profile created on the blade of the knife could not conclusively
determine Knox’s guilty verdict. This proves that DNA evidence and integrity of keeping the
DNA uncontaminated is vital; this is because it could change someone’s verdict to guilty or
not guilty based on the evidence presented, and whether there is enough of it that is still
viable to be used. (6)
Restrictions in DNA Data Use
There are limitations into using DNA as evidence, such as that it can be easily contaminated
and is unviable to be used in court. Therefore it is crucial that it is kept in a safe location,
which is sometimes not done. Furthermore there are specific retention periods for DNA data,
meaning if someone commits a crime and then is found innocent, the data is destroyed.
Therefore, this is not accessible forever and cannot be used in further cases to compare to
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