Lawrence A. Presley
Unit Chief, Quality Assurance Unit, FBI Laboratory, FBI Academy, Quantico, VA

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The application of DNA technologies to criminal cases is a significant issue because of the potential ability of the technology to include or exclude suspects, and because "...forensic scientists have little or no control over the nature, condition, form, or amount of sample with which they must work" (1). Given the importance and complexity of forensic samples, the first NRC report in 1992 attempted to address the issues of quality assurance and standardization by recommending formal quality assurance standards and programs, and external mechanisms such as certification, laboratory accreditation and governmental regulation.

In 1989, the Technical Working Group on DNA Analysis Methods (TWGDAM) published the first set of quality assurance guidelines for RFLP analysis. By 1992, the National Institute of Standards and Technology (NIST) had established a standard reference material for RFLP typing, and this standard has helped to standardize forensic RFLP DNA typing throughout the United States. By 1992, some forensic scientists were working towards certification and "some 77 forensic laboratories" (2) were accredited by ASCLD-LAB. Thus by 1992, many of the recommendations of the first NRC report were already well on their way to being firmly established in the forensic community.

The quality assurance recommendations of the 1996 NRC report focused on high quality standards to minimize the occurrence of errors, and proficiency testing and audits, and duplicate testing of forensic samples. To a large extent, these recommendations have been addressed by TWGDAM. TWGDAM has published numerous quality assurance consensus standards which have been used as the prevailing standards for forensic DNA analyses. TWGDAM developed and published a series of formal guidelines which address quality assurance (1989, 1990, 1991, 1995), quality audits (1993), mitochondrial DNA sequencing (1993), proficiency test manufacturing and reporting (1994), and a consensus approach for applying the "ceiling principle" (1994). For example, the 1996 NRC report strongly recommends the retention of a portion of the forensic sample, "whenever feasible", for additional tests (3). In 1995, the TWGDAM guidelines for quality assurance addressed the same issue and recommended that "whenever possible, a portion of the original sample should be retained or returned to the submitting agency ..." (4). By 1996, once again, the forensic community had already established, primarily through TWGDAM guidelines, quality assurance practices that are consistent with both the 1992 and 1996 NRC recommendations. There are also more forensic laboratories participating in accreditation, proficiency testing and audits, and more analysts certified, in 1996 than there were in 1992.

The 1996 NRC reports echoed the 1992 NRC reports’ view that accreditation could be a potential mechanism to ensure adherence to quality assurance practices. The 1996 NRC reports recommends that "laboratories should adhere to high quality standards (such as those defined by TWGDAM and the DNA Advisory Board) and make every effort to be accredited for DNA work (by such organizations as ASCLD-LAB)"(5). The DNA Advisory Board may finalize standards in 1997, and the DNA Advisory Board has voted to accept accreditation as a mechanism to ensure quality standards adherence. In 1997, it is likely that an organization, perhaps ASCLD-LAB, will take on the role of accreditation for forensic DNA laboratories, and provide a means, perhaps formal audit programs, to ensure adherence to DNA Advisory Board standards.

It should be noted that the 1992 NRC reports did suggest quality assurance related initiatives which ultimately resulted in the DNA Identification Act of 1994, certification as a potential quality assurance mechanism, NIST standard reference materials, and mandatory accreditation (New York). Some recommendations of the 1992 NRC reports such as increased NIJ funding, and federally mandated accreditation have not come to fruition as recommended by the 1992 NRC reports.

The quality assurance chapters of the 1992 NRC reports focused on mandatory federal accreditation, governmental regulation/licensing, NIJ funding and the National Committee on Forensic DNA Typing (NCFDT), while the 1996 NRC reports focused on TWGDAM guidelines, accreditation, proficiency testing, audits, error rates, and re-testing of samples. One clear distinction between the 1992 and 1996 NRC reports is in the area of error rates.

Error rates were discussed in chapter 3 of the 1992 NRC reports (DNA Typing: Statistical Basis for Interpretation), and error rates were discussed in chapter 3 of the 1996 NRC reports (Ensuring High Standards of Laboratory Performance). The 1992 NRC reports on error rates suggested that proficiency testing be used to measure error rates, and error rates should play a role in the interpretation of results(6). The 1996 NRC reports indicates that proficiency testing is not "designed to measure error rates"(7), and suggests that error rates should not be combined with match probabilities in forensic DNA typing calculations. It further indicated that the risk of error is properly considered on a case by case basis(8). The 1996 NRC reports concludes that "errors can be minimized by scrupulous care in evidence collecting, sample handling, laboratory procedures, and case review"(9).

Accreditation, certification and possibly regulation by some governmental authority still remain as quality assurance areas for the forensic DNA community to further consider and implement in some form throughout the forensic DNA community.

References