Should efforts to minimise DNA contamination of forensic swabs be standardised across Australia?

Across Australia, health professionals from differing disciplines provide health care for victims of suspected assault, which may include collection of samples for forensic analysis. Although some have been trained to collect forensic samples, few hold professional qualifications in forensic medicine. The current lack of standards and credentialled training for collection of forensic samples (in a manner that minimises the risk of contamination) poses an unacceptable risk to individual doctors and nurses, the profession and to the criminal justice system.

During the past decade, several high profile cases involving DNA contamination of evidence have been reported in the medical, legal and popular media. These cases highlight the costs in economic terms and in terms of human suffering, injustice and loss of confidence in the criminal justice system when errors occur because of DNA contamination.

A swab, and materials collected onto a swab, for forensic DNA identification might become contaminated at any time from the collection stage to the final stage of DNA identification. The process of DNA identification is a lengthy one that involves a number of people operating at different locations, at different times. There are many opportunities for a swab, or the genetic material obtained from the swab, to become contaminated with another person’s DNA.

It could be argued that there are two levels at which we should consider the need to avoid DNA contamination of swabs.

First, there is a need to avoid contamination of a swab with DNA from a member of the public who might be inculpated in a crime. These individuals cannot easily be excluded as suspects.

Second, there is a need to avoid contamination of a swab by DNA shed from a professional who has handled the swab or worked in the environment in which the swab was collected. By virtue of their employment, these individuals have a valid reason for their DNA being in the proximity of the swab. They might more easily be excluded as suspects, and most would readily volunteer to donate a reference sample to enable their DNA to be identified for the purpose of excluding them from further consideration in a criminal investigation. The compelling reason to avoid contaminating a swab with DNA from a medical professional or laboratory scientist is that the presence of any extraneous DNA affects the DNA scientists’ ability to interpret electropherograms. When mixed profiles are obtained, confidence in the scientists’ interpretation of the results is reduced. Some laboratories will not provide an interpretation of DNA results when a mixed profile of four or more individuals is obtained.

Wrongful convictions of innocent individuals have occurred because of DNA misidentification and other DNA-related errors in Australia and other countries — an outcome regarded as intolerable in a civilised society. Examples of wrongful convictions that appear to have resulted from DNA contamination are shown in Box 1.

Wrongful convictions have far-reaching consequences. In regions of the world where the death penalty exists, the outcome can be lethal.

As new case law increases everyone’s awareness of the phenomenon of secondary transfer of DNA, and techniques such as low-copy-number DNA amplification increase the risk of amplification of traces of contaminating DNA,6 defence lawyers are demonstrating greater willingness to challenge DNA evidence in court.

In the United Kingdom, at Terence and David Reed’s unsuccessful appeal ([2009] EWCA Crim 2698) against their 2006 conviction for the murder of Peter Hoe, the defence counsel argued that shards of plastic said to be from a knife handle and found near the victim were contaminated with the brothers’ DNA. Prosecutors argued that the DNA connected the brothers to the murder weapon. (The appeal was dismissed as there was sufficient evidence for conviction beyond the doubts over the DNA evidence.) In 2008, the UK police conducted a review of the use of low-copy-number DNA amplification techniques in light of the increased risk of erroneous interpretation of DNA identification results.7

In Australia, Canberra man Steven Hillier was acquitted of his ex-wife’s murder at a retrial in April 2010 (R v Hillier [2010] ACTSC 33). He had been convicted of murder in 2004. The conviction was quashed in 2006, and the Australian Capital Territory Director of Public Prosecutions subsequently challenged the appeal and sought a retrial. Hillier’s counsel successfully argued that a possibility existed that his DNA had been secondarily transferred onto his estranged wife’s clothing and doona.2

Prominent Australian lawyers8-10 have provided advice for barristers and judges on matters to consider during cross-examination and guidelines for determining admissibility of DNA evidence in Australian courts.

Quality assurance activities within laboratories minimise the risk of DNA contamination. National standards exist (National Association of Testing Authorities [NATA]) and DNA laboratory scientists must be credentialled.

Most scientists remain alert to the possibility of DNA contamination and openly acknowledge when contamination within a laboratory occurs. On rare occasions, scientists have denied responsibility for contamination or error. For example, the Victoria Police Forensic Services Centre (VPFSC) scientist involved in the contamination of a murdered child’s bib with a rape victim’s DNA suggested that an adventitious DNA match, not laboratory error, was responsible (inquest into the death of Jaidyn Leskie, Coroner Graeme Johnstone, July 2006). At the trial of a man wrongfully convicted of rape, the testimony of a VPFSC scientist suggests that the scientist had limited understanding of the potential for contamination at a site other than the VPFSC laboratory.5

Justice Frank Vincent’s conclusions5 about environmental contamination of the swab that led to the wrongful conviction of Farah Jama (Box 1) has been a powerful influence for change in the practice of clinical forensic medicine in relation to suspected sexual assault in Australia. There are a number of areas of improvement driven by the Victorian Institute of Forensic Medicine (VIFM), which has developed, in consultation with others, interim practice arrangements that act as guidelines for the collection of samples for forensic analysis.11 Key areas for improvement include the equipment and procedures used to collect samples and the environment in which samples are collected.

Swabs and slides within sexual assault kits should be as free of contaminating DNA as possible. Irradiation of swabs has proven to be an inadequate process for denaturing DNA. An unknown female suspect, linked to several unsolved serious crimes in Germany and Austria between 1993 and 2009, was eventually shown to be a worker involved with the manufacture of the swabs.12

Forensic-supply companies continue to develop and supply swabs, slides and kits that are increasingly easy to use and are designed to minimise the risk that DNA might inadvertently be transferred onto a swab via a swab sheath or equipment used during the procedure. Disposable single-use instruments such as pencils, pens, speculae, forceps and scissors are recommended. Documents for recording samples collected and envelopes used for transporting samples to a laboratory are treated to denature DNA.

Currently, there is significant variation between regions in Australia in relation to the design and suitability for purpose of some of the facilities where forensic samples are collected. Some facilities are clearly not “fit for purpose”. The structure of the facility should enable restricted access to a limited number of known individuals, adequate and documented cleaning to DNA elimination standards, furniture and surfaces that are maintained in a DNA-clean state, storage of equipment and supplies that prevents reuse or replacement of supplies that might have been contaminated and appropriate disposal of used supplies. Furniture and equipment within the examining room should be kept to a minimum and all surfaces should be able to tolerate cleaning with bleach. There should be a flow of patients from the entrance area into the examination room then shower facility. Suspects should not be examined in the area where victims are examined. These recommendations were set out in the VIFM submission to the Vincent inquiry.

Gloves must be worn and changed regularly, particularly during the interval between collecting samples from different sites and when labelling and packaging samples. In some overseas jurisdictions, medical practitioners shower and change clothing between cases. No agreement has yet been reached about the need for forensic practitioners to wear gowns, masks or hairnets. The requirement to use gowns and masks is likely to meet with opposition from paediatric forensic practitioners who are likely to express concern about the negative emotional impact that this apparel might have on child victims.

Cleaning procedures need to be at a standard that will denature DNA. Hypochlorite bleach has been demonstrated in DNA laboratories to denature DNA and is used for routine cleaning of floors and walls, as well as for cleaning work surfaces.

Techniques used to collect samples must ensure that material from one site is not inadvertently transferred to another site. Tamper-proof seals are used in some jurisdictions.

Following the release of the Vincent report, the Victorian Department of Justice sought to rectify problems within the Victorian centres where sexual assault victims are examined. To date, changes to cleaning practices and modifications to a small number of units have occurred, primarily as a direct request to health services, where most facilities are located. Although it was a clear recommendation in the Vincent report, no reduction in the number of sites where sexual assault victims are examined has occurred.

In July 2010, the UK Home Office published the second draft of the Codes of practice and conduct for forensic science providers and practitioners in the criminal justice system.13 The document was informed by a critical review of low-copy-number DNA amplification techniques and the use of this technology within courts. This comprehensive discussion document is regarded to be the first step in a process aimed at achieving better governance and higher standards throughout the sector.

In Australia and New Zealand, standards are being developed in line with the strategy for 2009–2012 developed by the Australia New Zealand Policing Advisory Agency National Institute of Forensic Science.14 Forensic science centres are assessed according to explicit criteria that test quality and the reliability of results in order to achieve NATA accreditation.

Within government in Australia, particularly Departments of Justice, there is an increasing awareness of the need for standards, monitoring and governance of those standards and the need for caution in relation to the use of DNA evidence in courts. The Public Defenders Office in New South Wales offered succinct advice to the legal profession in relation to the use of DNA evidence in court.15,16

In May 2011, the High Court, the highest court of appeal in Australia, dismissed convicted Canberra rapist Benjamin Forbes’ application for an appeal on the basis that he had been convicted on DNA evidence alone.17 This judgement indicates confidence in DNA technology and its use in the Australian criminal justice system.

At present, there is no governing or regulatory body for clinical forensic medical practice. Doctors are accountable to their employer and to the Medical Board of Australia. Nurses are likewise accountable to their employer and the Nursing and Midwifery Board of Australia. Most forensic practitioners belong to professional colleges, such as the Royal Australasian College of Physicians, the Royal Australasian College of General Practitioners, and the Australasian College of Legal Medicine. There is no overarching collegiate body to certify successful completion of forensic medical training.

The intercollegiate working group that developed guidelines for genital examinations of girls and young women did not provide explicit advice about the collection of samples for forensic analysis when sexual assault is suspected.18 The Australasian Association of Forensic Physicians has demonstrated an interest in developing standards and guidelines for collection of forensic samples, but this work is in its infancy.

It is unlikely that the medical profession will ever be able to exclude the possibility that a swab has become contaminated with DNA. The task before us is to minimise the risk, and to be seen to be minimising the risk, of DNA contamination.

Forensic medical practitioners urgently require national guidelines and standards to guide and govern forensic medical practice (Box 2). We also need:

• a national collegiate body to certify that practitioners have met training requirements and have demonstrated required competencies;

• a national group to negotiate across state boundaries with employers and governments to ensure that we are enabled and supported to provide a high standard of forensic medical care and to maintain an effective workforce;

• police and forensic scientists to share with us the desire to safeguard the integrity of forensic samples and the results obtained from their analysis;

• a well informed public that has realistic expectations of forensic services;

• a legal system that challenges, questions and pushes us to consider our failings; and

• a health system that supports and encourages us to continue to improve.