Examination of DNA yield rates for different skeletal elements at increasing post mortem intervals

Identification of contemporary human remains by DNA STR testing is mainly limited by the ability to isolate sufficient amounts of DNA from the skeletal samples. A key part of this work relies on selection of the skeletal element with the best chance of obtaining a DNA STR profile. DNA was extracted from 55 bone samples, from 3 recently skeletonized individuals, representing most element types in the human body. Comparison of DNA yields from samples within an individual showed that the small cancellous bones on average have much higher amounts of DNA per unit mass than dense cortical bones. Complete 16 locus STR profiles were obtained for all 3 individuals from 36 of the element types, 10 had full profiles for 2 of the 3 individuals, 3 had full profiles for 1 of the 3 and 5 did not have any full profiles. The sample types with the least STR loci were from the arms. Ten skeletal elements were tested from 12 additional skeletons ranging from 3-21 years post mortem interval (PMI). At increasing PMI the small cancellous bones continued to yield more DNA and STR loci than the cortical bones. These findings suggest that the current recommendation for selection of long cortical bone samples for DNA testing of skeletal remains should be re-evaluated.