Genetic analyses are performable from all the biological samples containing DNA. Thus, DNA extraction is the first and probably one of the most crucial steps of any genetic test. This chapter provides protocols for DNA extraction from both fresh blood and the big variety of biological samples that can be studied in the Forensic Laboratory. First, the general precautions which have to be adopted to prevent cross-contamination of the samples are underlined. All the extraction protocols (based upon Proteinase K/SDS lysis followed by ethanol precipitation) are carefully described while crucial steps are pointed out by footnotes. In addition, since PCR failure is common when handling aged/forensic specimens, strategies to remove substances acting as PCR inhibitors are described as well. At least, a simple and inexpensive PCR-based method allowing discriminating between removable and un-removable PCR inhibition is shown.
