DNA Extraction in Human Bodies: From Fresh to Advanced Stages of Decomposition

From the beginning of its application in forensics, DNA analysis has been considered the gold standard in human identification: it has become an indispensable tool in criminal investigation, disaster victim identification, and paternity testing. DNA typing can be divided into several steps that go from DNA extraction to PCR amplification and genotyping. The DNA extraction step is crucial because it determines whether there are any intact DNA molecules to be analyzed in the first place. Improvements in DNA typing success may be attributed to advances in PCR performance, which have been constantly increasing its sensitivity, tolerance to inhibitors, and multiplexing capability. However, DNA analysis will fail if the DNA is not efficiently extracted and purified from the biological sample. According to the ease of collection and decomposition state of the corpse, there are different biological substrates to choose from. Depending on the expected number of nucleated cells, biochemical composition of the tissue, and presence of inhibitory substances, each biological substrate requires a specific DNA extraction method. Therefore, the objective of this chapter is to give the reader a theoretical as well as practical basis for performing efficient DNA extraction from different biological substrates collected from fresh or decomposing bodies. The advantages and disadvantages of different methods as well as full protocols are presented so that the reader may choose one that is best suited for them.