DNA Analysis of Human Skeletal Remains in Slovakia: Laboratory Set-Up, Success Rates and Compliance of the Procedures with the ISO Guidelines

Aim: To evaluate the performance of a police laboratory that specializes in the DNA identification of skeletal remains in terms of success rates and compliance of procedures with international quality assurance standards and recommendations; to describe the correlations between sample type, post-mortem interval and level of decomposition of ostheological samples and autosomal STR typing in a dataset of 219 individuals (323 samples) in Slovakia; and to provide readers with comprehensive guidelines for the set-up and operation of a specialized bone identification DNA laboratory. This evaluation should serve as a reference for all planned specialized laboratories for the DNA identification of bone samples. Method: Skeletal remains were recovered from different locations throughout Slovakia, and the post-mortem intervals ranged from several days to 84 years. The preservation of these samples varied depending on the storage conditions prior to recovery. Therefore, the silica-based DNA extraction method that was successfully used in the identification of victims from mass graves in former Yugoslavia was used here as the method of choice. Results: The comparison of results from specific years indicated constant improvement in the overall success rate, from 71% in 2005/2006 to a maximum of 100% in 2009. There were several factors that influenced the success rate: a robust extraction procedure, continuous improvement of methods, bone sample selection, the introduction of DNA quantification and strict counter-cross contamination procedures. Conclusion: The results of this study clearly demonstrate that the proper application of scientifically sound procedures can lead to the efficient identification of unknown skeletal remains, thus solving serious criminal cases. The success of DNA typing was related to the type and the post-mortem interval of the skeletal sample; thus, the proper education of officers submitting case samples can result in an increase in the overall success rate as well as speed up the process of identification.