The Reliability of DNA Profiling
From its origins in 1984, when DNA fingerprinting was first invented by Sir Alec
Jeffreys, DNA fingerprinting has grown to become an essential tool in human identification.
DNA fingerprinting’s uses range from indentifying criminals or victims to matching an organ
donor with their proper recipient. Regardless of the guidelines set in place during the application
of DNA analyses, errors that could negatively alter the results of the analysis have a chance of
occurring. Given that DNA profile matching is a science based off probability, it is important to
know the weight of influence DNA has when it is the primary evidence for human identification.
Though the anthropological community, criminal justice system, and courts accept DNA
profiling as reliable evidence for human identification, the controversy facing DNA’s reliability
still continues.
In a research article by Jobling & Gill (2004), the processes of human identification using
DNA was highlighted. The weight of DNA evidence is explained by match probability (Pm) or
the probability that a second person will have the same DNA profile (Jobling & Gill, 2004, p. 2).
Match probability becomes higher if the DNA sample has degraded, if the perpetrator and
suspect are blood relatives, and if the perpetrator and suspect share the same ethnic background
(Jobling & Gill, 2004, p. 4). Jobling & Gill discuss a method for human identification called
Short Tandem Repeats (STRs). The match probability of the current STR method surpasses the
current population of people on Earth (Jobling & Gill, 2004, p. 5). The STR method has been
used in large scale identifications such as indentifying remains after the 9/11 World Trade Center
attack (Jobling & Gill, 2004, p. 8). Jobling & Gill explain that an estimated 1,000 people might
never be identified due to problems with DNA degradation. The reliability of DNA testing here
is convincing. Our current human identification methods are able to make profile matches with
the least likely chance of the match not being unique. That’s good to hear since DNA
fingerprinting is widely accepted as reliable evidence. The factors that could raise the match
probability, such as DNA degradation, are good to take note of as they sometimes can impede
successful DNA profile matches.
Next, the problems facing DNA fingerprinting is addressed by depreciating the DNA
analysis process. In a research article by Varsha (2006), the complications of using DNA
fingerprinting as a tool in criminal investigations was discussed. The article points out the
problems that relate to DNA fingerprinting. First, court cases require that the probability of a
DNA fingerprint being unique to a single person needs to be high. Next, proper training is
needed for collection of samples and analysis. Also the impurities found with the DNA can
hinder the identification process (Varsha, 2006, p. 7). The reliability of DNA evidence in this
case rests upon the people who work with DNA and the problematic environmental conditions
that can thwart a successful DNA analysis. In order to improve DNA fingerprinting’s reliability,
it is important to know of the hazard areas involving DNA analyses so proper corrections can be
made. Varsha, Jobling, and Gill would agree that a convincing match probability is important for
establishing the weight of DNA evidence.
Additionally, the topic of DNA evidence insufficiency is scrutinized in regard to its
applicable use in the court system. In a research article by Sucherman (2011), the validity of
“John Doe” DNA Arrest Warrants and unconstitutional claims against their use was talked about.
“John Doe” DNA arrest warrants are used to preserve sexual assault cases in which the
perpetrator is unknown but DNA evidence that could be used to identify the individual was
found at the crime scene (Sucherman, 2011, p. 3). In other words, the authorities have the right to
arrest someone if their DNA signature matches the evidence collected at the time a “John Doe”
DNA arrest warrant was issued. Sucherman argues that DNA evidence is insufficient for telling
us the events that took place during a crime, but it’s useful for identifying people that may have
been present at the scene. In the case of People v. Robinson the court reviewed claims of
“unlawful collection of DNA evidence” and “statute of limitations” violations (Sucherman, 2011,
p. 3). Robinson was tried for a sexual assault case in 1994 – six years after the fact. Even though
Robinson’s constitutional rights were violated, the DNA evidence identifying him as the criminal
was very convincing. An expert witness at the trail explained that the probability of the
incriminating DNA pattern matching two people at 13 loci was 1 in 630 quadrillion (Sucherman,
2011, p. 3). The reliability of DNA testing shown here concerns its use in finding unknown
criminals. DNA is accepted as incriminating evidence even with regard to a defending party’s
claims of injustice. This article agrees with Jobling & Gill’s claim of DNA testing having a low
probability of matching a DNA profile with two people.
Furthermore, the topic of using DNA analysis for practical use is examined in regard to
its repercussions. In a research article by Berger (2006), the impact DNA exonerations are
having on capital punishment, incarceration, and court rulings was addressed. DNA exonerations
are the reason behind the diminishing public approval of the death penalty (Berger, 2006, p. 2).
The possibility of sending innocent people to their death can leave a bad aftertaste. DNA
fingerprinting was a promising tool for exonerating the innocent. In the 1990’s, to reduce the risk
of error in DNA testing, forensic laboratories who handled DNA were subjugated to guidelines
set by the FBI (Berger, 2006, p. 2). Even though guidelines were put in place, many mistakes as
a result of fraud or incompetence of specific analysts were discovered by post-conviction
examinations of DNA analyses (Berger, 2006, p. 3). Berger suggests that flawed DNA analyses
may be at fault for an unknown number of convictions. She argues that crime laboratories need
to improve their procedures for hiring, training, supervision, and review of their personnel in
order to make sure that flawed DNA analyses are not being conducted. The reliability of DNA
testing shown here relies on the implementation of analysis techniques in laboratories that deal
with DNA. It is a shame that some analysts have made fraudulent DNA analyses. If they had just
done their job properly, then maybe innocent people would not have to go to prison. Hopefully
the post-conviction analyses being carried out will catch any mistakes and repair the damage
done by flawed DNA analyses. Berger and Varsha would agree that the people handling DNA
need proper training in order to produce correct DNA analyses.
Finally, the topic of implementing DNA testing guidelines is evaluated in regards to how
they counteract DNA related issues. In a research article by Weathered (2004), the difficulties
facing DNA exonerations when challenging the reliability of evidence in a DNA related case
were discussed. The estimated percentage for wrongful convictions in the United States is .5 –
5% (Weathered, 2004, p. 3). As of 2004, 148 post-conviction exonerations in the United States
were carried out using DNA evidence (Weathered, 2004, p. 2). Considering the population of
people incarcerated in the United States (2 million as mentioned in Berger’s article), this number
does not appear to represent the estimated percentage of wrongful convictions. According to
Weathered, DNA evidence in exoneration cases were only available 20% of the time. As a
solution to the wrongful imprisonment problem, programs called “innocence projects” were
created. The “innocence projects” were institutions whose primary purpose was to get innocent
people out of prison. Applicants to the innocence projects faced issues regarding their possible
exoneration such as not having the right of crime scene evidence perseveration, slow or no
access to evidence, and no right to have DNA innocence testing conducted at forensic labs
(Weathered, 2004, pgs. 9-10). An example of these issues can be seen in the case of Larry
Johnson. In 1984, Johnson was charged with rape and sodomy and spent 18 years in prison
before he was exonerated (Weathered, 2004, p. 10). Johnson had applied to the Innocence
Project in New York in 1996, but was not granted post-conviction testing until 2002. Weathered
states that forensic evidence has been either lost or destroyed for about 75% of old cases in the
United States. To combat the issues facing innocence testing, new laws were created in the
United States and Australia to insure that potential evidence that could prove innocence is well
preserved and is accessible when needed (Weathered, 2004, p. 2). The reliability of DNA in this
case falls upon our justice system’s ability to preserve evidence and conduct post-conviction
DNA testing for people applying to Innocence Projects. It is a sad thought that many innocent
people are suffering in prison without a simple means to prove that they were wrongly convicted.
DNA testing is not at fault for the wrongful convictions. In fact, DNA fingerprinting has been
helpful in providing some people with the evidence they need to get exonerated. If the new laws
created for innocence testing turn out to be successful, then maybe more of the .5 – 5% of people
wrongfully convicted in the United States will get their freedom back.
All the results indicate that DNA fingerprinting has already been accepted as a reliable
source of evidence but complications involving the analysis and use of such evidence need to be
taken into account. It is evident that the main argument for DNA fingerprinting’s unreliability is
its human related problems. Berger and Weathered would branch off from there and argue that
the Criminal Justice System’s use of DNA is at fault for the slow progress of exonerating
innocent people. Some of the problems with DNA fingerprinting listed in Varsha’s article are the
same as the main problems in Berger’s article. The problems with DNA fingerprinting are
known and actions are being taken to reduce the impact human error has on its reliability.
References
Berger, M. A. (2006). The Impact of DNA Exonerations on the Criminal Justice System. Journal
of Law, Medicine & Ethics, 34(2), 320-327. doi:10.1111/j.1748-720X.2006.00037.x
Jobling, M. A., & Gill, P. (2004). ENCODED EVIDENCE: DNA IN FORENSIC ANALYSIS.
Nature Reviews Genetics, 5(10), 739-751. doi:10.1038/nrg1455
Lynch, M., Cole, S. A., McNally, R., & Jordan, K. (2010). Truth Machine: The Contentious
History of DNA Fingerprinting. Retrieved from
http://system2.lib.hawaii.edu:2052/lib/lcclib/docDetail.action?docID=10366842&p00=tr
uth%20machine
Starr, B. (2011) Ask a Geneticist. What type of test can be done to determine if you are a
chimera? Retrieved from http://www.thetech.org/genetics/ask.php?id=443
Sucherman, M. (2011). People v. Robinson: Developments and Problems in the Use of "John
Doe" DNA Arrest Warrants. California Law Review, 99(3), 885-913. Retrieved from
EBSCOhost.
Varsha. (2006). DNA Fingerprinting in the Criminal Justice System: An Overview. DNA & Cell
Biology, 25(3), 181-188. doi:10.1089/dna.2006.25.181
Weathered, L. (2004). A QUESTION OF INNOCENCE: FACILITATING DNA-BASED
EXONERATIONS IN AUSTRALIA. Deakin Law Review, 9(1), 277-293. Retrieved
from EBSCOhost.