Forensic science: The coming paradigm shift

May 1st, 2014

By Claire Lewis and Cesarina Edmonds-Smith

The field of forensic science, like many others, is continually changing and improving. The current evolution is in the form of a much-needed paradigm shift. This much-needed attention in a field that has been hidden in the shadows for much of its duration seems to be bringing about this paradigm shift.

In an article written by Michael J Saks and Jonathan J Koehler (2005) 309 Science 892 at 895) describing ‘The coming paradigm shift in forensic identification science’ in the United States (US), four major forces that influenced the shift in the forensic identification (fingerprint, tool mark and ballistic analyses) were detailed. These four forces included a scientifically sound model for identification sciences; changes in the standards that make an expert testimony admissible; the discovery of incorrect convictions, later amended through DNA typing; and studies into the error rates of the various identifications sciences. They stated that these forces were pushing forensic science out of the realm of ‘pre-science’ to one of ‘empirically grounded science.’

Erroneous convictions do occur from time to time, especially when the evidence relies heavily on witness testimonies, however, what if the preferred methods of evidence analysis are not scientific? Then, inevitably, we land up with questionable results and often, wrongful convictions. In order to rectify some of these past wrongful convictions, cases have been reopened, and new scientific methods, such as DNA typing, applied. The application of new scientific methods may assist in some cases, however, DNA typing has incorrectly become known as the essential element of the wrongful convictions. While DNA typing is more scientific than the identification sciences, the exact odds of one person possessing the same DNA sequence as another is as yet unknown and therefore the accuracy of DNA typing must be approached with caution. DNA typing, while far more accurate than friction ridge, tool mark, or ballistic, analyses has its own flaws. This is particularly in cases where the sample is less than ideal, many of which are only now being discovered and is, therefore, not a 100% certainty and should by no means be relied on as the sole method to convict or acquit.

The use of DNA typing to correct erroneous convictions does display the inaccuracy of the original identification science methods. These wrongful convictions not only place doubt on past convictions but should also place doubt on future convictions, as although the methods have been shown to be inaccurate they are still in use by our forensic experts today. These identification science methods need to change in order to prevent incorrect convictions from occurring and it is hoped that the inaccuracy of these methods will drive the discovery of more scientific, accurate methods.

This leads to the question of whether identification science should even be considered a science at all. The comparison of friction ridges in fingerprint analyses or bullet striations in ballistics analyses is a subjective comparison whereas science is objective, by its own definition of dealing with a body of fact or truth. Although scientific methods may not find the exact truth, they should ­approach the truth as closely as is possible. Science is fact and should not favour one side or the other, but should rather remain impartial. Identification science methods, however, are performed by a single individual who determines whether or not two images match based on his or her opinion and experience. Opinion and experience are not scientific. Science is not meant to rely on experience. Therefore, new models for the identification sciences that are scientific need to be created in order to do away with the bias that comes with the current methods. This will drive forensics into new fields and will force research into new techniques.

In the US, forensic science testimony is measured in terms of the Daubert test as set out in Daubert v Merrell Dow Pharmaceuticals Inc 509 U.S. 579 (1993). A forensic practitioner’s testimony can now be gauged, with respect to a standard, to determine if it would be admissible in court or not. The Daubert test is comprised of three guidelines that –

  • the testimony is based on sufficient scientific facts or data;
  • the methods and principles utilised by the expert witness are reliable; and
  • the methods and principles are applied correctly and reliably (supra 584 – 587).

The judge has been assigned the role of deciding if the said testimony would be admissible or not. In order to determine the relevance and reliability of the evidence given by an expert witness, the judge would make use of the Daubert test. The Daubert test is comprised of four considerations: Empirical testing, peer review, known or potential error rates, and acceptability in the scientific community (supra 584 – 587).

Although the Daubert test is widely known and used in the US, there are currently no set tests in South African law by which expert testimony can be gauged. This is a major problem in many cases in South Africa as individuals who are not qualified to give expert evidence, according to the Daubert test, are able to testify. This lack of education/knowledge/experience by the ‘expert witness’ leads to evidence that has been incorrectly understood and/or incorrectly explained, leaving the presiding judge or magistrate, who is not versed in scientific reasoning and fact, to make their judgment based on incorrect science that will, in some cases, lead to the incorrect conviction or acquittal of the accused.

So far the encountered ‘expert witnesses,’ with the exception of a few, do not have degrees in science let alone postgraduate experience. Undergraduate studies, as South African forensic expert Dr David Klatzow puts it, teach you the language of your chosen field of science, and postgraduate studies teach you how to perform research and provide you with the licence to learn and apply your mind. Forensic science requires a multidisciplinary approach. For example, in South Africa, drunken driving or driving under the influence is a criminal offence and the courts rely heavily on the testimony of the doctor or nurse who drew the blood from the accused, as well as the laboratory analyst who ran the blood and determined the blood alcohol levels. Understanding the procedure of blood testing requires the knowledge of not just analytical chemistry but biochemistry, microbiology, statistics, physiology and chemistry all of which aid in the procedure and calculations. The employees at the South African Police Services  (SAPS) forensic laboratory have achieved, in most cases, a diploma in a single subject from a technical college. Therefore, the laboratory analysts very often do not understand the ‘language’ of their chosen field and sometimes cannot comprehend the questions being posed to them. They are not correctly trained, or even sufficiently trained to be classified as expert witnesses. Their training mirrors that of a laboratory technician. They follow standard operating procedures and, while this is excellent from a technical point of view, it does not ensure their understanding of the work that they are performing. A thorough understanding of multiple fields of science should be an absolute minimum requirement to be an analyst, which would be taught in any undergraduate programme in the field. This will ensure that the analysts understand all the facets of their work and the procedures they are following as well as being able to provide clear understandable testimony in court.

Another cause for concern with the training of these SAPS forensic laboratory analysts is that much of the training, if not all of it as with the ballistic, fingerprint and evidence collection units, is in-house training. This means that individuals who do not thoroughly understand their field, its protocols, and methodologies are teaching other individuals. This will inevitably create a dilution of the knowledge and of the correct operation procedures as messages will get lost or incorrectly portrayed along the way and result in substandard training and thus substandard analyses. In addition, some analysts may be hired with diplomas in fields that do not relate to the field in which they practise, this resulting in the analyst not possessing enough knowledge in the correct fields.

Sometimes the expert witness is a medical doctor and/or forensic practitioner, and while the medical fraternity does remarkable work every day, not every medical doctor is a researcher, and very few are true scientists. Medicine has its place in the law, just as science does but not many doctors or forensic practitioners are pushed to learn outside of their field of focus or specialisation. They interpret data based on the extensive knowledge they possess in their field of expertise. However, they do not often apply these interpretations to fields outside of their expertise that can influence an entire case. Therefore, the standards by which expert witnesses are measured require much revision. It is too often taken for granted by the courts that an individual is an expert witness but their qualifications are not taken into account and thus junk science is passed off as real science without anyone knowing any better. Just as a scientist’s knowledge of the law is limited so too is the courts’ knowledge of science and if one blindly believes what they are told by a so-called ‘expert witness’ without questioning whether the ‘expert witness’ is indeed an expert then anything said could be taken as evidence.

Studies have been performed into the error rates of identification sciences and some alarming results have been found. Michael J Saks and Jonathan J Koehler quote that spectrographic voice identification error rates are 63%, handwriting error rates are about 40% and sometimes approach 100%, bite mark false-positives run as high as 64%, and microscopic hair comparisons are about 12%. With regard to fingerprint analysis errors, about 25% of examiners failed to correctly identify all latent prints in a test, about 4 to 5% of examiners committed false-positive errors on at least one latent, and in one test, 20% of examiners mistook one person’s prints for those of his twin. These statistics display some of the error rates that occur in identification sciences. Other more infamous stories also detail how incorrect identification sciences have resulted in wrongful convictions or acquittals. These include cases of Brandon Mayfield, who was wrongly arrested for a bombing in Madrid, Spain in 2004; Hawley Harvey Crippen, who was wrongfully convicted and hanged for the murder of his wife; and Shirley McKie, who was wrongfully charged with perjury for allegedly lying about depositing her fingerprint at a crime scene. In addition the Daily Mail Online posted an article in which it detailed that 27 prisoners awaiting the death penalty had been found not guilty and were exonerated by means of DNA analysis (Louise Boyle ‘Shock report into FBI errors cast doubt on twenty-seven death penalty convictions’ 18-7-2013 Daily Mail Online., accessed on 19-01-2014). The Innocence Project, whose main objective is to correct erroneous convictions, stated that 250 people had been exonerated in the US by 4 February 2013 (, accessed 19-01-2014).

All of these cases display the inaccuracies of current forensic techniques that are universally utilised. These statistics are pushing the paradigm shift in the right direction, that is, towards more accurate scientific methods.

In addition to other complications, all of the above-mentioned factors that affect the paradigm shift worldwide are prevalent in South Africa. Forensics in South Africa need to participate with the rest of the world in rectifying these practices and ensure that these updated methods are employed. Forensic science is a growing industry in South Africa and the correct training methods need to be put into place to identify and challenge these identification sciences. Academic institutions also need to join the international community in providing research into new identification methods that are more scientific and able to withstand the criticism.

Claire Lewis MSc Med (ForSci) (Wits) and Cesarina Edmonds-Smith PhD (Chem) (UCT) MSc (ForSci) (Anglia Ruskin, Cambridge) are independent forensic consultants at ForScight in Cape Town.

This article was first published in De Rebus in 2014 (May) DR 38.