ICMP Science and Technology Director Dr Thomas Parsons reviews the evolution of DNA-led human identification techniques in the course of the last 20 years.
DNA testing for human identification is today used in forensic laboratories around the world, and may be familiar to many people through popular TV detective shows. However, there was nothing routine about the situation in 1999 when ICMP began to consider the use of DNA identification to help identify some of the 40,000 people missing as a result of the conflicts in the former Yugoslavia. At that time, it was not known if DNA testing could be applied on a massive scale in such a context.
When ICMP decided to attempt a DNA approach, DNA testing from degraded human bones was almost exclusively the domain of mitochondrial DNA (mtDNA) testing. mtDNA is present in thousands of copies per cell, so the chance that it remains in bones is comparatively high. The trouble with mtDNA is that it is not unique to an individual, and can be used for identification only together with other identifying information. This problem is exacerbated when there is a greater number of missing persons. In the Western Balkans, there was a huge number of missing persons, but there was little traditional identifying information that could be practically combined with mtDNA.
A small number of forensic labs around the world were beginning to explore the targeting of nuclear DNA (using the short tandem repeat – STR – markers that are now a mainstay of forensic DNA testing) from bones. There was also some experience from the analysis of ancient human remains that showed promise.
ICMP’s DNA laboratories jumped at the technical challenge, and quickly devised a new DNA extraction technique and enhanced PCR methods that produced STR results from most of the bone samples where this was attempted. This opened the way to a massive campaign to collect blood samples from family members of the missing and establish a DNA database of reference profiles against which DNA profiles from bone samples could be compared.
This was the launch of a new type of “DNA-led” identification that was quite different from the conventional approach, in which a hypothetical identity for a set of remains is developed and then subjected to a yes-no DNA test. However, this immediately posed an additional challenge – how to compare DNA profiles from bone samples against a large database of DNA profiles from family blood samples. Together with others, ICMP designeda computer program to do exactly this and in November 2001 this program produced its first DNA match – the identification of a teenage boy killed during the 1995 Srebrenica genocide. By the end of 2002, nearly 1,000 DNA identifications had been made.
The following years saw continuous refinement of the DNA process, including the development of a highly efficient modular laboratory workflow enabling high throughput bone testing. Progress was rapid, with a strong focus on addressing the limiting factors that presented themselves at any time, and a growing experience based on a wide range of difficult samples and genetic kinship analysis of complex cases. Over the years several improved iterations of DNA extraction methods were implemented and published.
The result was a dramatic increase in the rate of identifications. This in turn helped keep pace with the continued degradation of DNA in bones that were located and excavated from mass graves over the years. Additional DNA targets were added to the testing arsenal, increasing the number of standard STR markers that could be obtained, including parentage lineage markers such as Y-chromosome and mtDNA which were used to resolve many cases where additional information was needed for kinship analysis.
ICMP’s success in DNA identification was not completely laboratory based. The huge challenge of commingled skeletal cases from secondary mass graves required an approach that integrated physical anthropology and DNA sampling and testing to permit disarticulated skeletal remains to be re-associated and identified on a cost effective basis. Among the outcomes of this work was the world’s most extensive collection of data on the preservation of DNA in different bones of the skeleton, information which was used in turn to refine anthropological sampling effectiveness.
Forensic DNA analysis requires high standards of quality assurance, and at the turn of the millennium laboratories all around the world were coming under pressure to be accredited by rigorous oversight bodies and maintaining stringent standards. In 2006, when ICMP took the step toward accreditation, only around 30 percent of forensic DNA laboratories in Europe were accredited. Intense efforts led ICMP’s DNA laboratory and matching departments to be accredited in 2007 to ISO-17025 requirements, an international gold standard, with accreditation maintained to the present day. This is just one element of the quality assurance that has resulted in ICMP DNA results being accepted in major international war crimes trials.
Since 2004, ICMP’s DNA identification capacity has been applied throughout the world, including Thailand’s response to the December 2004 tsunami, the US response to Hurricane Katrina in 2005, and the Philippines’ response to Typhoon Frank in 2008. It has also been applied in many transportation disasters, and in cases of post-conflict identification such as those in Chile and Cyprus. In addition, forensic professionals from Libya, Iraq, Colombia, Vietnam, the Philippines and elsewhere have taken part in customized training programs offered by ICMP’s laboratory system.
Today, ICMP maintains a database of close to100,000 family reference DNA profiles, and over 50,000 profiles from degraded human remains. This has supported around 20,000 identifications globally.
ICMP continues to be a successful innovator in DNA identification. Among other things, it is developing a program based on “massively parallel sequencing” (MPS), a technique that has revolutionized the life sciences and which is set to further increase the power and reduce the cost of missing persons identification.
In the last 20 years, genetic science has changed exponentially, and ICMP has remained at the forefront of that change. It has successfully harvested the gains of technical innovation – and, importantly, it has done this in a field where these gains can mitigate human suffering and help to support recovery from conflict and disaster.