Establishing a Rank Order for Skeletal Element Sampling: Examining Differential DNA Yield Rates Among and Between Buried Human Skeletal Elements as Compared to Surface Recovered Skeletal Elements

As submitted by the proposer: DNA analysis plays a critical role in forensic identification, particularly when lengthy postmortem intervals and advanced decay are considered. Previously we compared DNA degradation among skeletal elements across three individuals, ranking the elements based on their overall DNA yield and ability to ascertain a full profile (Mundorff & Davoren 2014). We found that small cancellous bones yielded greater amounts of better quality DNA than larger, denser, cortical bones. We developed a rank order of skeletal elements according to the ability to obtain high DNA quantity and quality. However, these results were obtained using skeletons from individuals who decomposed on the ground surface. In several studies, DNA degradation in bones recovered from the ground surface actually conflict with data from buried remains. Moreover, we know that the burial environment strongly influences decomposition, so it is likely that differences in DNA yield between aboveground remains and buried remains are due to differences in degradation pressures from soil microbes and the intrinsic qualities of bone that contribute to DNA protection from degradation. Soil provides a challenging environment for DNA preservation. It is teeming with thousands of species of microorganisms that break down organic matter, including DNA, to derive energy and nutrients. Just as bone tissue type density influences DNA preservation, bone tissue type and surface area may also influence the rate and ability in which bacterial scavengers can physically access and colonize bone and feed on the DNA. The lack of a controlled study evaluating bones recovered from a buried context, coupled with the lack of consensus between previous studies on the most reliable skeletal elements for obtaining DNA, points to a gap in the existing forensic science knowledge base. This gap can only be bridged through a controlled study focusing on testing all skeletal element types from buried human remains for DNA quantity and quality, along with appropriate documentation of the physical and microbiological environment affecting the DNA preservation. Our proposed research will provide the needed comparison between buried remains and our previous aboveground data. A comprehensive comparison between these two decomposition environments does not currently exist. The proposed research will ultimately reveal the skeletal elements that will be most successful in yielding quality DNA from buried remains and will provide a clearer understanding of the mechanism of DNA preservation in bone and it’s susceptibility to degradation – a critical component in the forensic community’s ability to identify skeletal remains. Note: This project contains a research and/or development component, as defined in applicable law. ca/ncf