Impact of DNA Evidence on Crime Scene Investigation

Introduction
Evidence of the use of deoxyribonucleic acid (DNA) in forensic investigation dates back
to 1984 (Asplen,2003). The efforts of Alec Jeffrey, a British geneticist who was able to compare
samples of blood from individuals of the same family, led to the conclusion that DNA profiling
could be used to differentiate the genetic makeup of people (Asplen,2003). The objective of
Jeffrey’s s research was to investigate the transmission of hereditary diseases in the family tree,
which led to the discovery of DNA fingerprinting. Further findings revealed that 99.9 percent of
the DNA among humans would be identical, and only 0.1 percent of the sequences would vary
(Asplen,2003; Machado & Silva, 2019). The small percentage accounts for uniqueness in every
person. This paper will examine the impact of DNA in crime scene investigation.

The use of DNA in criminal investigations since the late 1980s has been instrumental in
solving crimes to the range of thousands (Asplen,2003). The scientific data obtained from DNA
has higher reliability as compared to other pieces of evidence collected from the crime scene.
Further, genetic mapping has also been considered to give accurate results as compared to
fingerprint recognition. Several studies (Murphy,2018; Campbell et al., 2019; Peterson et al.,
2010) have confirmed that DNA analysis plays an essential role in the justice systems across the
globe. In criminal court proceedings, juries often have high regard for forensic information
presented by an expert. This could be in the form of fingerprints, semen, blood, or hair collected
by a foreign investigator. This kind of evidence is circumstantial and may not necessarily prove
guilt. Therefore, their use has to be tied to a part of a case such as murder, theft, or sexual
assault. For example, the blood and hair examination and analysis can place a suspect in a

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general class and may not identify him/her as an individual. Blood typing puts an individual in
either blood group O, A, AB, or B, which is not sufficient in identifying the primary suspect
because thousands of people have that blood group (Beaver, 2010). On the other hand, DNA and
fingerprint analysis can identify a suspect through profile matching.

Notably, the procedure of forensic analysis starts with obtaining a sample of the DNA
from the victim or the crime scene, which are then taken to the lab. The primers that attach to the
same DNA sequences in the test sample are used to identify several genetic markers. The
enlargement of the original sample is done by using a string of primers joined to the DNA
sample. This is done by scientists to determine if the profile of the DNA exists by examining
thirteen genetic markers using a ‘short tandem repeat technology’ (Machado & Granja, 2020).
Laboratory analysis of the DNA aid in developing the sequence of events from the physical
evidence obtained from the scene. Such information aid the detectives in determining the
individuals involved. Mainly the information obtained from the lab is the identification and
classification of the specimen that originated from an individual (Beaver, 2010). Corroboration,
on the other hand, aids the prosecutor to hypothesize the positions of suspects and victims and
how the crime was carried out. If the results give a negative identification, this implies that the
items under investigation were not obtained from the same origin.

The success of the use of DNA has, however, in the past, generated unrealistic
expectations that dissociate from the congruence of a criminal investigation. For example, the
potential risks from the use of DNA evidence include the possibility of errors and threats to civil
rights such as genetic privacy, innocence, and physical integrity of the suspected individuals
(Dolan & Felch,2008). At the same time, contamination of the DNA from external sources such

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as during collection and analysis may lead to false identification, especially in cases of partial
profiles attributed to the degradation of DNA (Bykowicz & Fenton,2008; Helmus et al., 2019).

Types of DNA Analysis Used in Criminal Investigation

Familial DNA
This has been used by the government to arrest more than 250 million individuals in the
past years. The FBI currently has a list of more than 77.7 million people in the criminal database
(Machado & Granja, 2020). This means that information on one of every three adults is stored in
the database of the federal agents. Several individuals advocate for the collection of DNA
samples from every person to enhance testing and mapping, which can curb criminal activities.
In cases where no matches are found that link DNA from a victim or crime scene to profiles
within the databases, several countries are requested to perform a familial DNA searching to
identify close biological relations to the unidentified forensic sample obtained from the crime
scene. Familial DNA matching was first successfully used by the United Kingdom to prosecute
cold criminal cases in the 1970s (Asplen, 2003; Murphy,2018).
The DNA from the crime scene revealed a familial link to the criminal’s son, who had
previously been convicted for car theft. Similarly, the United States has embraced the practice in
her 12 states which currently allow familial DNA searching in their databases for genetic
matches to a relative of a person yet to be identified (Campbell et al., 2019). The results of the
matches can reveal a partial match, such as 12 of the 20 critical markers or a hundred in relation
to the evidence obtained from the crime scene indicating that a child, parent, or any other
individual has blood relations to the culprit. For example, the ‘Grim Sleeper’ case in 2016 was
solved using FDS (Murphy,2018 Campbell et al., 2019). The criminal had consistently

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committed criminal activities in California for six years by assaulting women sexually. The
forensic crew had DNA samples of the perpetrator from various crime scenes. Yet, they were
unable to positively identify the culprit because the samples from the crime scene did not match
the ones in the database. A breakthrough was eventually found after police conducted an FDS
that linked the suspect’s DNA sample to a relative (Machado & Granja, 2020).

DNA Phenotyping

This method has been used as a part of a criminal investigation where the witness present
at the crime scene describes the culprit. The recounting of events can be transcribed on a
photographic array or a composite sketch of the perpetrator obtained through an artist or a
computer-aided production system (Murphy,2018). This method has, in the past, led to the
wrong identity and convicted of innocent individuals. The drawings may poorly represent the
features of the suspect leading to a mismatch in encoding facial features and profiles when
generating a composite. At the same time, the witness recalling the events may be biased or
could be influenced by poor visibility. This led to having several unsolved cold cases if the
suspect is not identified. The current advancements in DNA have led to the creation of a ‘digital
mug shot’ that relies entirely on personal genetic information (Machado & Silva, 2019). The
molecular protofitting has a higher probability of predicting the physical features of the suspect,
such as gender, the color of the hair, and family tree based on the DNA samples obtained from
the crime scene. Similarly, the proponents of this technique argue for the feasibility of the
practice of reverse engineering of the DNA to the physical form of a suspect. This is done
through the analysis of genotypes from the sample DNA to predict the physical firm of the
criminal. According to Machado & Silva (2019), the phenotypic prediction has an accuracy level
of more than 90 percent.

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Despite these recent innovations on the use of DNA to match a suspect to the crime
scene, several ethical concerns have been raised on the use of the technique. For example,
forensic DNA phenotyping has been seen to proliferate risks of stigma and criminalization of
specific individuals, which makes them vulnerable to the actions of the criminal justice system
(Eitle, Stolzenberg & D’Alessio,2005). Equally, it is sensitive to disclose data related to the
physical profiles of potential suspects since they may go into hiding to escape prosecution. On
the other hand, familial searching raises efficacy and technical issues, for example, the need for
funds and human capital to examine and review the selection of several hundreds of prospective
suspects. Further, familial search techniques tend to infringe on the privacy of individuals since it
constitutes extensive genetic surveillance to individuals whose information would not have been
revealed, were it not for the actions of the blood relatives.

Conclusion

The use of DNA analysis in generating crime scene evidence has led to the identification
and conviction of several suspects involved in criminal activities. Familial searching and DNA
phenotyping have been instrumental in the identification of suspects who could have easily
escaped the justice system. Despite this breakthrough, ethical concerns and infringement of civic
rights have been raised over the years. The lack of genetic privacy and stigmatization that results
from physical profiling of the suspects have been documented in previous cases. Therefore, the
knowledge concerning existing research on the impact of DNA testing in forensic science is
paramount in the generation of sustainable models of governance. This means that the
development of DNA databases and forensic DNA practices should be done in liaison with the
public. Further reviews on DNA forensic analysis should focus on perception for the attachment

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of suspect profiles within a specified period as well as the conditions that favor their retention or
deletion.

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References

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of Justice, at 15, http://www.ncjrs.gov/pdffilesl/nij/grants/203971.pdf
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