Challenges in DNA extraction from forensic samples

DNA extraction from forensic samples is the most critical step of all the analytical process since it impacts on the quantity and quality of DNA obtained from a sample: good DNA produces good interpretable profiles. Forensic evidences are highly variable and unpredictable; thus the choice of the DNA extraction procedure depends on some factors such as the type of the biological sample, the wide ranges of substrates where the sample may be placed, the amount of the biological evidence being examined, exposure to varying environmental conditions, variable degradation, and the presence of PCR inhibitors. The use of an appropriate method able to optimize DNA recovery from forensic samples is therefore essential in order to obtain high DNA quantity free of inhibitors useful for downstream applications. Several DNA extraction procedures (manual and automatic) have been developed during years in order to improve DNA extraction especially from challenging samples.