This paper discusses what fingerprinting is, when it is used and the pros and cons of using it, using a variety of different references. It goes into the forensic science behind fingerprinting and gives assessment and analysis.
What is fingerprinting?
In a nutshell, fingerprinting, when matched positively to a suspect, is forensic evidence used in the investigation and trial of a crime. It must be remembered that “forensic science” has not always really merited the term “science”, as until recent years it has really been rather an inaccurate science. It has only been as recent as the 1990s that three developments focused on the shortcomings of “forensic science”:
The advent of DNA profiling, the Supreme Court’s “Junk Science Decision” and several well publicized crime laboratory scandals. (Gianelli, 2005). The term fingerprinting today does not really refer only to the marks that someone may leave on a window. It refers to DNA fingerprinting. It also cannot be ignored just how much of an impact forensic profiling and DNA fingerprinting can have upon a trial.
To understand DNA profiling, I believe that one first has to know that large portions of any single person’s DNA are the same as every other person’s. Because we’re all human beings and belong to the same species, a large chunk of our DNA is dedicated to our species-specific traits – we have feet instead of hooves, skin instead of scales, etc.
But other sections – or fragments – of human DNA are unique to the individual. These fragments are called polymorphic because they vary in shape from person to person. Essentially, DNA profiling is the process of separating an individual’s unique, polymorphic, fragments from the common ones. (Baden, 2006)
Currently, two types of genetic profiling are being used and scientists are always defining and refining other techniques which can be used.
Specifically, what is DNA fingerprinting?
Professor William Moody and Dr John Medina, are quoted in a website, Basics of DNA Fingerprinting, compiled by Kate Brinton and Kim-An Lieberman in 1994 as stating the following:
The chemical structure of everyone’s DNA is the same. The only difference between people (or any animal) is the order of the base pairs. There are so many millions of base pairs in each person’s DNA that every person has a different sequence.
Using these sequences, every person could be identified solely by the sequence of their base pairs. However, because there are so many millions of base pairs, the task would be very time-consuming. Instead, scientists are able to use a shorter method, because of repeating patterns in DNA.
These patterns do not, however, give an individual “fingerprint,” but they are able to determine whether two DNA samples are from the same person, related people, or non-related people. Scientists use a small number of sequences of DNA that are known to vary among individuals a great deal, and analyze those to get a certain probability of a match. (Moody and Medina, 1994)
The introduction of DNA profiling into the courtroom was not without controversy. In one of the first cases challenging DNA evidence, People vs Castro, the court reported the following: In a piercing attack of each molecule of evidence presented, the defense was successful in demonstrating to this court that the testing laboratory failed in its responsibility to perform the accepted scientific techniques and experiments.
Even top FBI officials, whom one would think the technologies would possibly assist the most in the resolution of their cases, agreed that DNA testing had shortfalls. Stringent standards have had to be developed and put in place to regulate this form of testing (Gianelli, 2005)
The Supreme Court’s Junk Science Decision
This decision occurred in the Daubert vs Merrell Dow Pharmaceuticals case – the Daubert court established a reliability test for the admissability of expert testimony. Forensic techniques became subject to scrutiny, something which was subject to argument from agreeing and opposing sides. There is also the Frye test which offers greater protection for defendants.
Thus, either under the Daubert or Frye method, forensic evidence is being scrutinized in a way which it never was before.
Forensic science abuse cases
The third development in forensic science was as a result of forensic science abuse cases – “tainted or fraudulent science” of which Fred Zain’s conduct at the West Virginia Crime laboratory is probably the most notorious. Amongst other things, he overstated the strength of results, altered laboratory results, reported that multiple items had been tested, when in fact only one had, etcetera.
He had been a treasured witness in this case, so much so that even after he left evidence was sent to him for testing (Gianelli, 2005). This case and others like it have led to some important reforms including accreditation of crime laboratories, proficiency testing, standardization of technical procedures, adequate funding, research, defense experts, pretrial exposure, etc. (Gianelli, 2005).
When is fingerprinting used?
There are many instances when fingerprinting is used, but I would say that the most convenient and practical application of this would be in particular in crime cases, in instances when there is no other supporting evidence. For example, consider the case of David Hicks who was convicted by a jury in Freestone County of the rape and murder of his grandmother.
No weapons or physical fingerprints linking Hicks to the crime were ever discovered by the police. There was also no witness who was able to place him at the scene of the crime. Based on this, under ordinary circumstances, a case such as this would have been dropped.
But the jury had one piece of evidence which was substantial enough for a death sentence to be returned: Prior to the trial, a sample of Hicks’ blood was compared to semen removed from his grandmother. These were analyzed for weeks, treated with enzymes, electric fields and radioactive markers, and reduced to “fingerprints” – electronic “smudges”, which, when compared, appeared to match. At the trial molecular biologists gave testimony that the odds of such samples matching were 96 million to one. It was only due to the presence of this evidence that the trial was able to reach such a satisfactory conclusion. It was even stated by one of the officials by the time that had it not been for the DNA evidence available they would not have been able to obtain a conviction in the case – Hicks would have walked free. (Ford and Thompson, 1990)
There are other instances too where DNA testing can be used, such as in paternity tests, although this would not be described as a DNA fingerprint.
Another possible application for this, although, according to the website Practical Applications of DNA Fingerprinting, unlikely to occur in the near future, is that of personal identification. At the moment, the technology required to isolate, keep on file, and then analyze millions of very specific genetic patterns is currently very expensive and impractical.
What are the pros and cons of fingerprinting?
The resilience of DNA is one advantage that DNA fingerprints hold over their older ‘pen and ink’ variety counterparts. For example, ten year old semen in a pair of underpants, tested using the modern technology of today, was used to clear a man wrongly convicted. Also, while fingerprints found in someone’s home can be explained away innocently, traces of one’s blood and semen upon the victim’s clothing is not so easily explainable. (Ford and Thompson, 1990). This evidence is also supported by the use of an expert testimony in court, giving further credibility to it.
Obtaining samples from prisoners before they leave after having completed their sentences is also beneficial – the theory is that subsequent crimes may be easier to solve, (Ford and Thompson, 1990).
Another, indirect, advantage of this is job creation – new lab technologists need to be continually trained up to develop new technologies and learn the existing ones.
There are certain cons that go hand in hand with this however. There are a number of disquieting questions about DNA fingerprinting. There are fears that techniques have been rushed into court and claims for the accuracy of them are exaggerated.
One concern is the amount of difficulty that is involved in accurately interpreting a print. Forensic DNA may be so contaminated, that when compared with pristine laboratory samples, accurate analysis is impossible. There are also doubts about analyses that give astronomical odds against errors. There are also justifiable concerns about how this evidence is going to be treated in court.
In one case in 1989, a judge, Gerald Sheindlin, ruled that DNA prints could not be introduced in one case, and he recommended pretrial hearings in all such cases. In November of the same year the Minnesota Supreme Court ruled that DNA cases would be inadmissible in Minnesota State Courts until scientific questions about the procedure had been resolved. (Ford and Thompson, 1990).
Obviously, in the past 12 years, great steps have been made in this regard and technology has been developed still further, but will we ever be able to get to a level where DNA testing is 100% accurate? We are not there yet.
According to the Birth Defects Genetic Centre in the University of Alabama (2003), who use DNA testing for parentage testing, the accuracy or specificity of the DNA testing depends on the sample and procedure that the DNA laboratory has used.
They go on to state that since we utilize the most advanced genetic testing procedure, we are able to achieve at least specificity of 99.9%. In most cases, DNA testing will result in specificities of 99.99% or greater. While 0.01 % is extremely low, it is still not 100%, but it is likely that this is as close as technology is going to get and it is a lot more accurate than previous methods ever could have claimed to have been.
Further problems lie in the following: VNTRs, because they are results of genetic inheritance, are not distributed evenly across all of human population. A given VNTR cannot, therefore, have a stable probability of occurrence – its make up and composition will vary to quite a large degree depending on an individual’s genetic background. (Brinton and Lieberman, 1994)
To exacerbate this problem, the difference in probabilities is particularly visible across racial lines. Some VNTRs that occur very frequently among Hispanics will occur very rarely among Caucasians or African-Americans. We can see that this would be problematic when utilizing the tests for forensic evidence. (Brinton and Lieberman, 1994)
Currently, not enough is known about the VNTR frequency distributions among ethnic groups to determine accurate probabilities for individuals within those groups; the heterogeneous genetic composition of interracial individuals, who are growing in number, presents an entirely new set of questions. (Brinton and Lieberman, 1994)
Further experimentation in this area, known as population genetics, has been surrounded with and hindered by controversy, because the idea of identifying people through genetic anomalies along racial lines comes alarmingly close to the eugenics and ethnic purification movements of the recent past, and, some argue, could provide a scientific basis for racial discrimination. (Brinton and Lieberman, 1994)
While it can be seen that the new technology in use has many distinct advantages over the methods that were used in previous years, there are also some cons that go together with this.
DNA technology is relatively new and there are always teething problems that go along with new things which have to be ironed out. But if we allow these teething problems to become so large that they actually deter us from what we want to do, then progress will never be made in anything.
I believe that a certain amount of moderation and caution must go together with using the technology, but that at the end of the day progress is good. Correct utilization of DNA fingerprinting will allow more accurate convictions of guilty persons to take place, swifter and more efficient resolutions to crime cases, and in cases where there is doubt as to whether the right person has been convicted, and there is the presence of an old DNA sample, the accurate result can be obtained and the mistake redressed. There are possibly unknown applications for DNA testing that will come to light as further progress is made in the field.
Baden, (2006), DNA Profiling, retrieved 12 April 2006 from the website http://www.kathyreichs.com/dnaprofiling.htm
Birth Defects Genetic Centre, (2003), “How accurate is DNA Testing” retrieved 12 April 2006 from the website http://www.southalabama.edu/genetics/bdgc/ptest003.htm
Brinton, K., and Lieberman, K, (1994), Basics of DNA Fingerprinting, retrieved 12 April 2006 from the website http://protist.biology.washington.edu/fingerprint/dnaintro.html
Ford, S, and Thomson, W (1990) A Question of Identity, New Scientist March 31 1990, Vol 125 38 – 43
Gianelli, P. (2005) Medical Malpractice, US and International Perspectives
Moody and Medina, (1994), retrieved 12 April 2006 from the website written by Kate Brinton and Kim-An Lieberman http://protist.biology.washington.edu/fingerprint/dnaintro.html